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VAN NOSTRAND'S

Engineering Magazine.

VOLUME XXVII.
J"TTI_i"5T— IDIEOIEDVEQIEIFl.

1882.

J.3 1^

N E W V 0 R K :

D VAN" NOSTRAND, PUBLISHER
23 Murray Street and 27 Warren Street (up stairs).

1882.

CONTENTS

VOL. XXVII.

Page

Aerial Navigation 1

*' After effect," magnetic 169

Air currents in sewers 423

Alloy for glass and porcelain

surfaces 440

Alloy for silvering 438, 524

American railway system.... 84
Analysis of Potable water — 228

Analysis of water 143

Apparatus, base line 89

Arches under embankments.. 210 ;

Arlberg tunnel 79, 347 i

Armor plates 521 I

Armor-plate trials 436

Armstrong ribbon gun 172 |

Art castings in iron 434

Artillery, modern 296

Atlantic steamer, novel 260 ■

Australian railways 173

Automatic brakes 262

Base-line apparatus 89

Basin of the Mississippi 18

Batteries, secondary 48

Belgian Academy prizes 87

Birmingham sewage works ... 42

Bismuth filings 264

Blasting on Danube 519

Blasting under water 99

Boilers, marine 499

Boiler protection 524

Book Notices:

Abbe, Cleveland, Solar Ec-
lipse of 1878 263

Aine, Armengaud, Metallur-
gie . 85

Boiling, Carl A., Metallur-
zischer chemie 522

Broadhouse, John, Acous-
tics 437

Church, Arthur, M.A., La-
boratory Guide 351

(lark, D. K., Revision of
Courtney's Boiler Maker's
Ready Reckoner 263

Crookes, W., F.R.S., Dyeing
and Tissue Printing 175

De Cew, Gustav, Dynamo-
elektrischen maschinen. . . 522

De Parville, Henri, L'Elec-
tricitie et ses applications 351

Drinker, H. S., Tunneling. . 437

Edwards, E. Price, Eddy-
stone Lighthouse 85

Facey, J. W., Jr., Element-
ary Decoration 263

Geikie. A., LL.D., F.R.S..
Geological Sketches 437

Geikie, Archibald, LL.D.,
Text book of Geology. . . . 522

Gerber, Dr. Nicholas, Chem-
ical analysis of milk 523

Gerhard, Wm. P., House
Drainage 263

Gorringe, Henry H., Lieut.
Com. U. S. N., Egyptian
Obelisks 85

Harcourt, L. F. V., C. E.,
Rivers and Canals 86

Hasluck, Paul N., Metal
Turner's Handbook 351

Hospitalier, E., On Electric-
ity 350

Kimball, Rodney G., A.M.,
Olmstead's College Philos-
ophy, 3rd Revision 350

Knight, E. H., LL.D., Me-
chanical Dictionary 85

Page

Koppe, S. W., Glycerin 522

Larden, W., M.A., School

Course on Heat 263

Ludlow, Henry IL, Sub-
scales 522

Pierce, Benj., LL.D., Linear

Associative Algebra 264

Plum, Wm. R., LL.B., Mili-
tary Telegraph 263

Reynolds, Michael, Continu-
ous Brakes 350

Robinson, S. W., C. E., Rail-
road Economics 263

Routledge, R., Translation
of Du Moncel's Electric

Lighting 263

Sabourain, A., Voeabulaire

Raisonne de Magnetisme . 85
Shelton, A. J., F.C.S.,

Household Chemistry 174

Vidal, Prof. Leon, Cours de
Reproductionlndustrielles 85

Wright, Lewis, Light 437

Brakes, automatic 261, 262

Breech-loading gun, peculiar. 227

Bridge across the Forth 257

Bridge over Firth of Forth .... 81

British navy 258

Bronzing iron 173

Buildings, protection of 154

Building stones 426

Cadmium and Tin 264

Candle power of electric light

33, 105

Car wheels 521

Cast-iron water pipes, enam-
eled 349

Channel tunnel 431

Cheap railway 433

Clemenson's system 172

Cleveland Institution of Engi-

. neers 352

Co-efficient of safety in navi-
gation 416

Color blindness 348

Coloring cements 439

Compressed air engines 438

Concrete sewers abroad 208

Conservancy of rivers 281

Constant supply of water 115

Construction of harbors 71

Corrosion of steel and iron ... 82

Cost of electric lighting 113

Currents in Suez Canal 171

Curves and crossings for rail-
ways 56

Dangerous properties of dusts 438
Deaths and injuries on rail-
ways 261

Destruction of carbon elec-
trodes 77

Detection of color blindness. . 348

Dikes of the Isle de Re 279

Direct process 191

Drainage, house 265, 392, 461

Durability of building stones. 426
Dynamo electric machine 88

Eddy stone Lighthouse 120

Edmonton sewage works 42

Efficiency of secondary bat-
teries 48

Elasticity of various metais.. 201

i Electric light 33, 105, 503

i Electric light meter 197

i Electric lighting, cost of 113

Page
Electric railway in Ireland ... 434

Electric railways , 15

Electrical Exposition at Paris 372

Electrical perturbations 280

Electrical thermometers 32

Electrical transmission of en-
ergy 341

Electricity of flame 437

Electro dynamic attractions. . 439

Electro dynamometer 351

Embankments, failures in 413

Energy, storage of . . . 64

Engineering, mechanical 482

Engineering notes in Ceylon. . 262
Engineering, past and present 124
Engineering structures in

Italy 430

Engine, gas 77, 442

Engine, gas, theory of 354, 442

Experimental mechanics 377

Explosive, new 352

Failures in embankments 413

Flow of liquids in pipes 87

Floating compass 439

Force of air currents in sew-
ers 423

Formation of sand banks 71

Formulae for pile driving. 298-387

Forth Bridge 519

Foundations for piles 22

Framed roofs 510

Future electric railways 15

Gas engine 77

Gas engine, theory of 354, 442

Geology of Tokio 176

German ironclad 418

German magazine gun 349

Glass, new variety of 302

Girders and roofs 510

Girders, plate-web 49

Gordon's formula 419

Great lakes of America 437

Harbors on sandy coasts 71

House drainage 265, 392, 461

Hundred ton gun 171

Hydraulic propulsion 202-437

Improvement of rivers 102

Incandescent lamps 372

Incandescent light 113

Incandescent lighting 503

Industrial exhibition at Lille. 352
Influence of manganese on

iron 435

International heat of the

earth 439

Invention of a German chem-
ist 176

Involution of polynomials 185

Iron and steel 55

Iron and steel at high tem-
peratures 82

Iron and steel in Russia . . , 258

Ironclad, new 436

Iron importation 520

Isle de Re, dikes of 279

Isotropic elastic substances.. 352
Italy, buildings in 103

Journals under trains 433

Lacustrine canoe 17

Lakes, heights of 523

Lamp, new 440

Lamps, incandescent 372

CONTENTS.

Page
Largest lock in the world. ... 432

Light by incandescence 503

Light, electric 33, 105

Lightning conductors 523

Lightning, protection against. 154

Light-house, new 120

Limit of elasticity 201

Magnetic " after effect " 169

Manufacture of locomotives. . 348
Manufacture of steel and iron 174

Marine boilers 499

Materials for structures 177

Materials, strength of 135

Measurements, standard 186

Measurements, wind 100

Mechanical engineer 482

Mechanical improvements — 1

Mechanics, experimental 377

Melting steel by electricity. . . 173

Metal alloys 264

Meter, electric light . . , 197

Michelson's thermometer 88

Mississippi, basin of 18

Modern artillery 296

Modulus of elasticity 201

Moncrieff system 435

Monument to Alexander L.

Holley 212

Navigation, aerial 1

Navigation, safety in

Nordenf elt torpedo boat 83

Observatory at St. Petersburg 88

Painting iron surfaces 349

Panama canal 258

Paris tramways 172

Perpetual motion 176

Pile driving formulae 22

Pile driving practice 298, 387

Plate-web girders ... 49

Plumbing law, new 104

Plumbing, sanitary.... 265, 392, 461
Polynomials, involution of — 185

Power, transmission of 247

Prismatic bodies, torsion of. . . 31

Preserving india-rubber 264

Pressure of wind 140

Process, new 191

Propulsion, hydraulic 202

Protection of buildings from

lightning 154

Pump for compressing gases 385
Pure carbons for the electric

light 174

Purifying water 173

Page
Quality of iron and steel 55

Radiophone in telegraphy 32

Radius of gyration 419

Railroads of the F. S 348

Railway curves 56

Railway embankments 413

Railway enterprise 173

Railway of Euphrates valley. 520

Railway statistics 520

Railway, St. Gothard 253

Railways, electric 15

Rarefaction of air 264

Regimen of the Mississippi — 18
Rensselaer Polytechnic Insti-
tute 212

Reports of Engineering
Societies:
American Society of Civil
Engineers,

81, 170, 257, 347, 430, 517
Engineers' Club of Philadel-
phia 80. 170, 257, 347, 518

Resistance of viaducts to

wind 213

Rivers, conservancy of 281

Rivers, improvement of 102

Rock drills.. 347

Roofs and girders 51o

Russian arsenals 408

Rusty bolts 63

Safety in navigation 416

Sahara inland sea 81

Sanitary plumbing.... 265, 392, 461

Secondary batteries 48

Seismological science in Ja-
pan 88

Self-winding clock 174

Sewage contamination 143

Sewage works 42

Sewer gas 423

Sewers, concrete 208

Sewers, ventilation of 409

Silvering alloy 524

Standard measurements 186

Stanhous hydrate 176

Steam tramways in London. . 433

Steel-faced armor plates 259

Steel making in Staffordshire 173

Steel plates for boilers — 82

Steel, quality of 55

St. Gothard railway 253

Stone arches under embank-
ments , 210

Stones, building 426

Storage of energy 64

Page

Strength of materials 278, 513

Structures in Italy 103

Structures, materials for 177

Submarine blasting 99

Submarine warfare 83

Subscales, including verniers.

196, 303
Superfluous members of trus-
ses 314

Supply of water. 115

System of water meters — . . 224

Tests of materials for struc-
tures 177

Theory of gas engine 442

Thurston's address 482

Torpedo defence 522

Torsion of prismatic bodies . . 31

Tram car axle 348

Transmission of electricity. . . 168
Transmission ©f energy, elec-
trical 341

Transmission of power 247

Trials of machine guns 260

Trusses, with superfluous

members 314

Tunnel under Boston mount-
ain 257

Tunnel under the Elbe 432

Tunnel ventilation 440

Twin screw steamers 259

Fnderground railway in Paris 376
Fniversal theorem 185

Ventilation of sewers 409

Vernier, new form of 196, 303

Viaduct across Solway Firth. 170
Viaducts, resistance of, to

wind 213

Vibrations by railway trains . 352

Water, constant supply of 115

Water, contamination of 143

Water meter system 224

Water, potable, analysis of . .. 228
Water supply of Alexandria.. 257

Water supply of Venice 171

Weights of framed girders. . . 510

Weyrauch's formulas 513

Wind, effects of on viaducts. . 213

Wind measurements 100

Wind pressure 140

Work of mechanical engineer 482

Yield of steel plates 258

Zinc in boilers 524

VAN NOSTRAND'S

Engineering Magazine.

NO. CLXIIL-JULY, 1882 -VOL. XXVII.

A STUDY OF THE PROBLEM OF AERIAL NAVIGATION, AS
AFFECTED BY RECENT MECHANICAL IMPROVEMENTS.

By WILLIAM POLE, F.R.S., M. Inst. C.E.
Horn Selected Papers of the Institution of Civil Engineers.

In a few remarks appended by the
author of this paper to the discussion on
Mr. Thomycroft's communication " On
Torpedo Boats and Light Yachts for
High Speed Navigation," he ventured to
express the view that the remarkable re-
duction lately effected in the weight of
power-producing apparatus, might have
an important influence on the solution of
the problem oir the navigation of the air.
He considers it may not be out of place,
as a matter of mechanical investigation,
that he should offer to the Institution
some account of the facts and reasonings
on which this view is founded.

The serious discussion of the possi-
bility of commanding locomotion at will
through the air is often avoided from the
fear of encountering popular ridicule.
But the engineer and the student of me-
chanical science will know that there is
nothing unreasonable or inconsistent
with mechanical principles in the idea.
The problem of producing motion in a
given direction through the air is analo-
gous with that of producing motion in a
given direction through the water, and is
subject to the same general laws. Hence,
as the latter problem has been long ago
Vol. XXVII.— No. 1—1.

practically solved, one may fairly inquire
how far the former one is likely to admit
of solution also.

The complete form of the problem of
aerial navigation is, of course, that of
flying, and the study of the mechanical
conditions of that wonderful process is
one of the most interesting offered by
nature. But as hitherto no approach has
been made to any artificial imitation of
it, its discussion would be out of place
here ; and it is proposed to confine at-
tention to a modified form of the prob-
lem, in which one of its chief difficulties
has been removed. The invention of
the balloon, about a century ago, over-
came the great obstacle to aerial oper-
ations caused by the action of gravity,
and so immensely simplified the con-
ditions to be studied, as to bring the
problem much more within the reach of
practical skill. It is therefore to aerial
navigation by means Of balloons that
this paper applies.

The analogy between motion in water
and in air has already been pointed out ;
and it becomes closer when the aeronaut-
ic apparatus has the power of floating.
| Now it is known by every-day experi-

VAN NOSTEAND'S ENGINEEKING MAGAZINE.

ence that if, in the case of a boat or
steamer, an action can be applied, by a
force within the vessel, against the sur-
rounding water, the reaction will propel
the floating body in an opposite direc-
tion ; and similarly if a force carried in a
balloon can be made to act against the
surrounding air, it is equally certain that
a propulsion in the opposite direction
will be given to the balloon.

And it follows that if motion can be
given through the air, there will also be
a steering power; for the well-known
contrivance of the rudder will be as
effective, if properly proportioned, in the
rarer as in the denser medium. Hence a
balloon thus constituted will be capable
of navigating the air in any required di-
rection, or will be (to borrow a very ap-
propriate term from the French) a dirig-
ible balloon.

The problem, then, in regard to such a
balloon is, to ascertain by what means an
action can be caused against the air by
some force within the balloon itself ; and
to investigate the result of this force in
effecting the propulsion.

The discussion of this problem now to
be offered is of no speculative character,
and contemplates no novelty of invention.
It will be based entirely on existing facts,
and on trials made on a full practical
scale, which will furnish the data for
reasoning on the future possibilities of
aerial navigation. Hence it is proposed
(I.) To state what has been done ; (II.)
To infer from this what may be done ;
and (III.) To offer some considerations
on the subject of a practical character.

I. WHAT HAS BEEN DONE.

It is worthy of record that the analogy
between water and air navigation was
perceived by a great mind, at the time
the balloon was invented. As early as
December, 1783, i.e., only six months after
Montgolher's first public experiments,
Lavoisier, the most eminent chemist
and physicist of the day, gave before the
French Academy an admirable resume of
the conditions which should be fulfilled
in aerostatic machines, and which are as
perfectly applicable now as they were
then. In studying the subject he saw
clearly that, by reaction against the air,
an independent motion might be given to
the balloon, and might be made use of to
modify the direction impressed upon it

by the wind, or in other words to render
it dirigible. Accordingly, the last of his
conditions ran thus :

" Finally, by employing the force of
men, it appears certain that it will be
possible to cause the direction of the
balloon to vary from the direction of the
wind, under an angle of several degrees."

Lavoisier's idea was discussed by the
Montgolfiers, who proposed to adapt
oars to their balloons ; and other early
aeronauts from time to time made experi-
ments in the same direction ; but none
of these efforts were successful. Hence
the great expectations which had been
raised as to the new power of locomotion
gradually dwindled away, and an opinion.
set in that aerial navigation by balloons
was, in the nature of things impossible.
This view prevails widely at the present
day, and it is not unusual to see the most
preposterous and unmechanical notions
gravely put forward in support of it.
But the explanation of the failure of the
early attempts is obvious enough ; it lies
simply in the difficulty of finding any
adequate means of applying the power.
Oars were unsuitable with total immer-
sion, and no mechanical ingenuity could
imitate the beautiful action of a fish's fin,
or a bird's wing. To make the balloon a
manageable locomotive agent required a
degree of advancement in mechanical
practice which has only been attained in
very recent times.

It was not till half a century after the
invention of balloons that the introduc-
tion of the screw propeller removed the
first difficulty, by providing an efficient
apparatus for acting against the air.
This apparatus was at once of the sim-
plest character, suitable for total im-
mersion, easily worked, and capable of
applying, in the most effectual way, al-
most any amount of power that could be
desired. After its introduction the prac-
ticability of aerial navigation could be no
longer doubtful.

The first person who made a serious
attempt to utilize the screw for balloons
was a young French engineer whose name
has since become famous in the engineer-
ing world on other grounds, M. Henri
Giffard, the inventor of the "Injector,"
one of the most elegant contrivances
ever introduced into engineering. It was
about 1850 that M. Giffard turned his at-

THE PROBLEM OF A. E RIAL NAVIGATION.

tention to the matter, but he found there
was much to be done before the experi-
ment could be carried out with any
chance of success. In the first place he
saw that the ordinary form of the balloon,
namely globular, was very unsuitable
when lateral motion through the air had
to be effected ; the well known analogy
of vessels for water navigation demand-
ing that the shape should be elongated,
diminishing at the bow and stern. To
complete the analogy, it was also necess-
ary that this elongated vessel should
have a keel and a rudder. As a power
to work this screw, he took the bold step
of using a steam engine, adopting, how-
ever, ample precautions against fire,
among which was the ingenious expedi-
ent of turning the funnel downwards,
and producing the draft by a steam blast,
as in the railway locomotive.

His balloon was 12 meters diameter
and 44 meters long. The car was sus-
pended by a net in the usual way, and
there was a large triangular sail attached
to the stern, serving as keel and rudder
combined. The steam engine was 3 HP.,
and worked a two-bladed screw 3.4
meters diameter, which could be given
one hundred and ten turns per minute.
The general appearance of the balloon will
be seen from the accompanying figures.

M. Giffard ascended from Paris on the
24th September, 1852. Having arrived
at a convenient height, he started his
engine, and the independent motion pro-
duced thereby became at once evident
by the prompt obedience of the balloon
to the action of the rudder. It was
"under way," and could be steered like
a ship at sea. He found that the screw
gave an independent velocity through
the air of from 2 to 3 meters a second, or
41- to 6 J miles an hour.

He intended to continue his experi-
ments, but he found that, in order to get
the best results, many improvements
were necessary which would take time.
His attention was then occupied on other
mechanical subjects, but in 1867 and
1868 he had occasion to construct two
large captive balloons, in which were
perfected some of the improvements he
had in contemplation, in particular the
impermeability of the envelope, a more
mechanical construction of the valves,
and a better and cheaper mode of pre-
paring pure hydrogen.

During the siege of Paris in 1870, bal-
loons were used to a large extent, as is
matter of history, in order to get de-
spatches out of the city. They were, un-
fortunately, not available for communi-
cation in the other direction ; but it oc-
curred to the authorities that if they
could be given even a slight independent
motion they might be made so, and this
led to another experiment under the au-
spices of M. Dupuy de Lome, the emi-
nent naval architect to the French Govern-
ment. He constructed a balloon, of an
elongated shape, 14.84 meters diameter
and 36.12 meters long. The car carried
a screw propeller of two sails, 9 meters
diameter, intended to be turned by four
men, a relay gang being also taken up to
relieve them. The experiment was inter-
rupted by the Communist Insurrection,
but it was completed afterwards, and the
ascent was made on the 2d February,
1872. Careful observations were taken
during the voyage, and they established
beyond a doubt the efficiency of the pro-
pelling apparatus in giving a velocity to
the balloon independent of the wind. It
was found that when all eight men w^re
working together at the screw, giving it
27^ revolutions per minute, an independ-
ent velocity was obtained of 2.82 meters
per second, or about 6.3 miles per hour.

As a matter of fact M. de Lome did
not accomplish much beyond what M.
Giffard had done many years earlier ; but
his work has a peculiar merit of its own,
namely the full and able manner in
which, applying to the subject his great
knowledge of marine navigation, he has
discussed all the elements of the prob-
lem. And by the lucid detailed descrip-
tions and explanations he has put on
record, both of his calculations and of his
experimental results, he has given a firm
basis for the extension of the principle
to a wider range.

The importance of these two trials, as
bearing on the practicability of aerial
navigation, cannot be denied ; but doubts
have been expressed whether the results
given can be implicitly accepted. It is
said (1) that the determination of the in-
dependent speed must be so difficult as
to be liable to error ; (2) that the results
of the two trials, with such different
amounts of power, are very discordant,
and (3) that had such marvelous ac-
counts been credited at the time they

VAN nostrand's engineering magazine.

must have been followed up. In M.
Grffard's case, there is, it is true, only the
unsupported statement of an engineer of
known reputation and great skill ; but
with regard to M. de Lome's trial, a ref-

credible that the full detailed particulars
communicated to such a body as the
French Academy, by a man of such high.
position, can have been otherwise than
trustworthy. The discrepancy between

M. H. Giffard's Dirigible Balloon, 1852.

erence to the "Comptes Kendus" will
show abundant evidence of the correct-
ness of his statements. He pre-arranged
with great care the modes of observa-
tion ; he was accompanied and assisted
by several other persons, and it is in-

the two trials will be explained else-
where; and the apparent neglect of the
experiment is easily accounted for by the
circumstances of the time, and the want
of any sufficient inducement for its re-
newal. The best answer, however, to

THE PROBLEM OF AERIAL NAVIGATION.

these objections is, that the results are
perfectly consistent with mechanical
principles, as will now be shown.

II. WHAT MAY BE DONE.

Under this head it is proposed to
investigate generally, as a mechanical
problem, the capabilities of balloons for
aerial navigation.

Assuming

that

a suitable elongated
shape, of circular section, has been de-
termined on, let the maximum diameter
be represented by <7, and the length by
I. Then the contents will be pro-
portional to d1 1 and the ascending
force of the gas may be expressed
by Ad2 1 ; where A is a coefficient
coefficient depending on the shape of the
vessel, and on the specific gravity of the
gas compared with that of the surround-
ing air.

The weight of the envelope will vary
as the maximum diameter multiplied by
the length ; and for the sake of simplic-
ity, one may, probably without much
error, apply the same proportion to the
net, the car, and all other parts of the
structure generally, including the pro-
peller, apart from its motive power.
Therefore, using another coefficient to be
obtained from experience, the weight of
the structure may be expressed by B d I.

Hence the available ascending power \
=Ad*l-Bdl, or=(Ad-B)dl.

Now this available ascending power |
has to support the weight of

1. The motor.

2. The necessary stores, "such as fuel,

water, &c.

3. The cargo.

The proportionate weight to be al-
lotted to each of these respectively will
depend on various considerations which I
it is impossible to reduce to any general j
rule. For the present purpose attention .
may be confined to the first item, the
motor ; and there may be allotted to it a ;
proportion of the whole available weight
represented by r ; so that the weight of i
the engine, or whatever the motor may i
be, will be = r(A.d—B)dl.

If then S represents the weight of the
motor for each (useful) HP., then,

v
Useful HP. of motor carried = -(Ad—

The next question is how the power of
the motor is to be expended.

The first element in the calculation is
the resistance of the balloon to motion
through the air. This is a point of great
importance, and it will be necessary to
treat it more at length hereafter. For
the present, it may be safely assumed, in
accordance with the analogy of bodies
moving in fluids generally, to vary, for
moderate speeds, as the square of the ve-
locity, and it may be represented by Xv2,
where X is a coefficient depending on the
dimensions and form of the balloon.

The HP. necesssary to propel the bal-
loon at a given velocity v, will be equal
to the resistance multiplied into the
velocity, and divided by a certain con-
stant number dependent on the units in
which the quantities are taken. Call this
H. (For resistance in lbs. and velocities
in feet per minute, H = 33,000. For
velocities in miles per hour, H=375 ; in
feet per second H = 550.)

Hence,

HP. =

Xe;3
H

B)dl

(I.)

which represents the power necessary to
propel the balloon through the air.

The next question is as to the effi-
ciency of the propeller. This has been
often investigated for water navigation.
Rankine, in his elaborate article on
" Propellers," gives the efficiency of the
screw of the " Warrior " = 77 \ per cent.
Mr. Isherwood makes that of two small
boats by Maudslay and Penn = 65J- and
71^ respectively. Mr. Froude reduces it,
for high-speed working, to 57J, but this
great loss is attributed to causes which
would hardly apply to air navigation.
M. de Lome estimated the efficiency at
72 \ per cent., taking a probable " slip
ratio " of 21 \ per cent. But as will be
hereafter shown, the actual slip in his
trial was a little greater, and therefore
the efficiency may be put down at 70 per
cent., which is fairly borne out by nauti-
cal experience. According to this, for
every 7 HP. directly expended in pro-
pelling the vessel, 10 HP. must be ap-
plied to the screw shaft, and the equa-
tion becomes —

r, m , ™> . • -. 10XU3

Useful HP. of motor earned = — == —

7.H

.... (ii.)

VAN nostkand's engineeking magazine.

Equating now (T.) and (II.) and reduc-
ing—

If all dimensions are expressed in feet,
weights and pressures in lbs., and ve-
locities in feet per second, then H = 550,
and

•» = ^(Ad-B)dl. . . . (III.)

An equation which expresses, in com-
pact form, the relations between the chief
elements that enter into the problem.

The next step is to obtain the values
of the important coefficients A, B, and
X.

Ascendiug power. — Supposing the bal-
loon to be tilled with pure hydrogen, the
levity of one cubic foot will be = 0.0751
lb. The Content of the balloon, accord-
ing to M. de Lome's proportions, was
about 0.434 d'l cubic feet, so that on this
supposition the floating power would be
= 0.0327 d2l. In fact the floating power
was = 0.03 d2l, the difference being no
doubt due to the impurity of the gas.
The coefficient may therefore be taken
at its lower value, i.e.,

A = 0.03.

Weight of the structure. — There is no
means of calculating this a priori, as it
comprehends such a variety of items, de-
pendent entirely on practical consider-
ations. The coefficient must therefore
be taken from examples on record. In
M. de Lome's balloon the weight was
3885 lbs. = 0.673 dl: in M. Giffard's it
appears to have been less. The former
is the more authoritative, therefore

B = 0.673.

Resistance of the balloon to motion
through the air. — This is the most im-
portant element of the whole investiga-
tion, and is at the same time the most
difficult to determine, from the scarcity
of experimental data on a' large scale.
It is, however, some palliation of the
difficulty to know that the resistance of
vessels propelled in water is also a quan-
tity liable to much variation and uncer-
tainty, notwithstanding the large amount
of experience gained in water navigation.
The proper course to adopt here is to
apply mechanical analogies as carefully
as possible.

The resistance of ships to motion
through water may be estimated accord-
ing to either of the three elements of
their dimensions: — (1) The area of
immersed midship section ; or (2) the
skin friction ; or (3) the cubic displace-
ment. It will be advisable to apply each
of these to the case of the balloon, and
see how they correspond.

(1) By the midship area. This plan
was adopted by M. de Lome, and the
following is a resume of the way he
treated it. He proposed in the first in-
stance to get a velocity of 8 kilometers
(4.97 miles) per hour. He took the re-
sistance to a plane surface passing per-
pendicularly through the air a*t this
speed at 0.665 kilogramme per square
meter. But, as is well known, this is re-
duced in a very large proportion by the
pointed form. The elaborate modern in-
vestigations of Mr. Froude have shown
that, theoretically, the head resistance
may be almost annihilated if the most
suitable form is adopted ; and M. de
Lome gives, as a matter of practical
experience, the fact of a reduction, in
well-formed steamers, to an amount vary-
ing between one-fortieth and one-eight-
ieth of the resistance due t© the mid-
ship section. For his aerial structure,
however, he was content to allow a
double proportional resistance, taking
the coefficient for the balloon at one-
twentieth. For the car, accessories, and
suspending apparatus he took a coeffici-
ent of one-half. This brought out the
resistance as follows : —

Square meters. KiL

Balloon 154 X 0.665 XgV^5-12

Car,&c 14X0.665X i=4.68

Total resistance =9.80

= 21.6 lbs.

This would be the quantity Xv2 for a
velocity of 7.3 feet per second, and a
midship diameter of 48.67 feet. From
which it follows that the resistance, esti-
mated according to this method,

= 0.000171 dV.
The calculation may be checked in
another way. According to the data of
wind pressures usually adopted by En-
glish engineers, namely, those given by
Smeaton to the Royal Society, in his
paper on Windmills, the pressure on each

THE PKOHLKM OF AERIAL NAVIGATION.

square foot of flat surface = ^-v*, where
v is in feet per second.

The area of the midship section will

be= J2 ; and that of the car, &c, may

be taken at one-eleventh of this. Hence,
allowing the same reductions for the
form as M. De Lome did, the total re-
sistance—

in _, n _\ v'1

= 0.000172 «JV,

agreeing almost identically with M. de

Lome's estimation.

(2) By the skin friction. — This is a

mode which has been sanctioned by
recent scientific investigations. Pro-
fessor Rankine has stated that if W =
wetted surface of a ship in square feet,
the resistance in lbs. may be taken as =

CW(sr>eed in knots)" . ~ .
AJs — — where C is a con-
stant something greater than unity,
whose exact value depends on the lines
of the vessel. For the "Warrior," 9,000
tons, he found it =1.275 ; for the "Fairy,"
168 tons = 1.124. Taking the higher
value and putting v = the speed in feet
per second, the resistance will be

~ 224*

Now if air be substituted for sea water
the resistance will be diminished in the
ratio of the densities, i.e., 793 to 1 ; and
further, the surface of the balloon ex-
posed to the friction of the surrounding
fluid may be taken as proportionate to
d I ; in M. de Lome's structure it was
about = 2.3 dl. Hence on tins mode of
estimation, the resistance for the balloon,
taken on the same coefficient as the
" Warrior," will be

2.Sdlv*

= 224x793

= 0.00001295 dlv\

Adopting then M. de Lome's allow-
ance for the balloon, of double the pro-
portional resistance for a good ship, and
adding, as he also does, 88 per cent, for
the car, &c, the resistance comes out ac-
cording to this mode of estimation

= 0.0000477 dlv\

(3) By the displacement. — This mode
combines both the former elements of

midship section and skin surface. If D
= displacement of a vessel in tons, and
v her speed in knots per hour, then the
rule given is

Resistance in lbs. = CxvTM

where C is a coefficient varying from
0.8 to 1.5, according to the form and
condition of the ship. Taking C = 1 for
a moderately good example, and chang-
ing D to cubic feet, and v to feet per
second, the resistance is

v2V%

30.5

The displacement of the balloon has
been given already as = 0.434 d2 1, and
proportioning for the densities of air and
sea water, the resistance becomes

= 0.0000238 rf* J*

Increasing as before, and adding for the
car, &c, it is

= 0.0000886 {& l)f v\

These three values of the resistance
may be compared in the case of any bal-
loon where the proportion of length to
diameter is given. In M. de Lome's
balloon, for example, I = 2.43 d.. Sub-
stituting this and reducing, the resist-
ance becomes, when estimated

By midship section = 0.000172 d2 v'2;
" skin friction = 0.000116 cF o'2;

" cubic displacement = 0.000160 d'2 v'2.

The estimation by skin friction is the
smallest, for the obvious reason that in
this structure the proportion of length to
transverse dimensions is so much less
than is usual in ships. The general com-
parison, however, shows that the esti-
mate by midship area adopted by M. de
Lome, is fairly corroborated by other
methods quite independent, and it may
therefore be safely taken as representing
the resistance.

It is now possible to apply the for-
mulae to M. de Lome's case, and see how
j the results correspond with those of ex-
: periment. The values of S and r must,
however, be first obtained from his
data.

The motive power he used was eight

men, and he states that, when they were

all working together, they produced

eight-tenths of a horse power. The men

i weighed 1325 lbs., which gives —

VAN nostrand's engineering magazine.

S = 1656.
And as his total available ascending
power was 2,046 kilograms =451 5 lbs.,
the proportion r allotted to his motor

was Hff— °-3 nearlv-

Returning now to equation III., arid
making Z=2.43 d, and X=0.000172 d\ it
becomes —

v8=440,000^(Ac/-B).

Wherefore, inserting the values of A, B,
r, and S, previously given, the velocity-
comes out =9.2 feet per second, or

= 6.25 miles an hour,
which is almost identical with the speed
actually obtained on the trial.

This agreement of the calculated and
the observed velocities shows, in the
first place, that the result obtained by
M. de Lome is in perfect accordance
with what might be expected according
to ordinary mechanical laws ; and sec-
ondly, it gives a practical warrant for
the more extended application of the
reasoning. It is clear that since the
power exerted is known, the estimate
made of the resistance must hold good,
at any rate for moderate .velocities ; and
although there are no experimental data
for higher speeds and greater power, yet
the analogy of experience in marine en-
gineering will justify the wider applica-
tion of the rules, if the principles on
which they are constructed are sound.

It is therefore proposed to examine
what might be expected to be the per-
formances of dirigible balloons, if, in the
provision of their power, due advantage
were taken of the most recent improve-
ments in mechanical engineering.

It will be evident that the kind of
power used by M. de Lome was exceed-
ingly disadvantageous, by reason of its
great weight. He fully admitted this,
but his object was a limited one, and,
under the circumstances, he took, no
doubt, the wisest mode of attaining it ;
for an independent velocity of a few
miles an hour would, by taking proper
advantage of the wind, certainly have
sufficed to enable balloons to enter the
city. For more extended applications,
however, human power is out of the
question, and it is necessary to go back
to M. G-iffard's plan of using steam, with
which, for this purpose, no other kind of
motor at present in use could compete.

But although steam power is lighter
than that of men, still down to a late
period it has been too heavy to be of any
real utility in a case of this kind, where
the carrying capability is so limited. Ac-
cording to the usual practice with en-
gines used for steam navigation, it may
be reckoned that the motor employed
has weighed 4 to 5 cwt. per HP., which
is also about the weight of small fixed
engines in the ordinary market at the
present day. At this rate the amount of
power which could be carried in a bal-
loon would be so small as not to do much
towards the successful solution of the
problem of aerial navigation.

But recent improvements have much
changed matters in this respect ; for in
cases where economy of weight has been
desirable, the skill of engineers has suc-
ceeded in effecting it to a very remark-
ble extent. In the modern locomotive,
for example, much has been done to in-
crease the power that can be developed
by an engine of a given weight, and if
those parts are excluded which properly
belong to the vehicle, and not to the en-
gine, the weight would probably come
out not more than about 1 cwt. per HP.

But even this has been much improved
upon within the last few years, as will
be seen by the paper by Mr. Thorny -
croft, already referred to. It shows that
in the arrangements of power for the light
boats there described, the author has
succeeded in bringing the weight of the
whole propelling machinery down to
43.5 lbs. per indicated HP.; which, omit-
| ting the screw and its long shafting and
| bearings, would probably give not much
j more than 40 lbs. for the motor alone.
I In the discussion which followed the
reading of the paper, opinions of high
I authority were expressed that further re-
I ductions were possible, particularly in
! regard to the boiler; but the figure* al-
ready obtained will suffice for the pres-
ent obj'ect.

It is, however, necessary, in order to
make this correspond with the terms of
the forgoing formulae, to transform it
! into the weight per useful HP. The loss
j between the power indicated in the cyl-
inders and that available at the end of
i the crank-shaft varies, of course, in dif-
ferent engines, but it is usually reckoned
from 15 to 25 per cent. Professor
I Rankine estimated the loss on the en

THE PROBLEM OF AERIAL NAVIGATION".

gines of the 4i Warrior '' at 22J per cent,;
Mr. Isherwood made that of Maudslay's
and Perm's engines 13 and 14i per cent,
respectively. Mr. Froude estimated it
higher, namely, 33.3 per cent.; of which
7.1 per cent, was due to the several
pumps. In engines of the light and
simple character of those here contem-
plated, without any air, bilge, or condensa-
tion pumps, probably 20 per cent, allow-
ance would be ample: i. e. for every 4
HP. applied to the screw shaft, 5 HP.
must be indicated in the cylinders. This
brings the weight to something over 50
lbs. per useful HP.

But there is another point to consider.
If steam power is used, the weight of a
store of fuel and water must be also
taken into account in the burden to be
earned. 1 he consumption of fuel for
the lightest engines is given by Mr.
Thornycroft at a little under 4 lbs. per
indicated HP. per hour ; probably some
kind of liquid hydro-carbon might be
most advantageous for this purpose, and
might also lead to a reduction in the
weight to be carried.

The water, however, is at first sight a
more formidable consideration, the
quantity necessary being from 25 to 28
lbs. per HP. per hour. Such a large ad-
dition would, a few years ago, have
rendered steam ballooning almost im-
practicable ; but fortunately here again
recent improvements have come in aid.
The water used in steam engines is not
like the fuel, decomposed and dissipated ;
it is only changed in form, and can be re-
produced by cooling. M. Giffard saw
this, and with the skill of an accom-
plished practical engineer he proposed
to introduce a system of air condensa-
tion. The Abbe Moigno gave, in the
"Mondes " of 15 Oct., 1863, an account
of various improvements which M. Gif-
fard had then on hand, and the follow-
ing passage refers to this point :

"The provision of water which it is
possible to carry in the air being neces-
sarily very limited, it is desirable to use
the same water, by condensing the steam
after it has produced its mechanical ef-
fect. This new improvement has been
carried out as rapidly as the former ones;
any of our readers may, whenever they
please, see, in the Avenue de Suffren, No.
40, suspended to the ceiling of the work-
shop, a series of flat tubes offering a

large surface, which condense the steam
I of a 1 0-horse engine."

The air condenser has been used in
this country by Mr. Perkins and Mr.
i Cradock, and it has within the last
; year or two been successfully applied by
j Messrs. Kitson & Co. to tram cars run-
ning in the streets of Leeds. It is
therefore no longer a mere theoretical
possibility, but an accomplished fact in
steam engineering. From data the au-
thor has obtained it appears that with a
moderate surface about three-fourths of
the water may be recovered, and that a
condenser adapted to this purpose may
be estimated to weigh about 20 lbs. for
each useful HP. of the engine.

From these data the weight may now
be made up more accurately. The
weight of the engine, with the con-
denser, may be taken at 75 lbs. per use-
ful HP., i. e.

S=75,
instead of 1656, as in M. de Lome's bal-
loon.

The store of fuel and water necessary
to be carried may be estimated, accord-
ing to present data, at from 10 to 12 lbs.
per HP. per hour ; but there is little
doubt that this quantity, as well as the
weight of the engine, could be reduced
if the necessity for doing so should
arise.

In proceeding now to apply the for-
mulae to new cases, it is necessary to de-
termine a proportion of length to diam-
eter. This in M. de Lome's case was
made 2.43 : in M. Giffard's balloon, it
was 3.66. There can be no doubt of the
advantage of length in diminishing the
proportion of resistance to capacity, and
in giving better steering properties ; and
even M. Giffard's proportion (which he
found answer perfectly well) is very
small when compared with those com-
mon in water navigation. In the fol-
lowing calculations, therefore, the pro-
portion -.=3§ will be adopted.

Cli

This will lead to a new comparison of
the estimated resistance, as determined
by different methods. By substituting
the value of I in terms of d in the vari-
ous resistance equations, it will be found
that the following values appear —

By midship section = 0.000172tfV ;

By skin friction = 0.000175tfV ;

By cubic displacement = 0.0002 UefV.

van nostrand's engineering magazine.

Here, it will be observed, the effect of
the increased length is to bring out
higher values of the resistance accord-
ing to the two latter modes of estima-
tion. On this ground it will be safer to
adopt them in preference to the former ;
and in the absence of any special experi-
ence as to which of the two is the more
applicable, the mean may be taken, i. e.

X=0. 000193c/2.

It is further necessary to determine r,
the proportion of ascending power to be
devoted to the motor, and this may be
conveniently made one-third. A sixth
may then be added for a store of fuel
and water, which would suffice to keep
up the maximum power for three or four
hours, but would last much longer under
ordinary working, when advantage would
be taken, to the utmost extent possible,
of the direction of the wind. (This store
of consumable material might take the
place of the ballast used in ordinary
aerostation.) The remainder of the net
ascending power, one-half, would be
available for cargo.

It may be advisable to add to the con-
stant B, to allow for some increased
weight that may probably be necessary
in the propeller, to meet an increase of
power and speed. Instead of 0.673, let
B = 0.72,

an increase of 7 per cent, on the whole
weight of the structure.

Substituting the above values in equa-
tion III., it becomes, in round numbers,
for the maximum possible speed through
the air —

v3 in feet per second =975(t/— 24) ) ,TV
vl in miles per hour=313(d-24)j ^ V,->

It remains to say something of the
necessary size and velocity of the screw
propeller. This instrument must, no
doubt, be large, owing to the compara-
tive rarity of the medium against
which it is to act ; but an idea may be
formed of its proportions according to
the analogy of water navigation.

In regard to the diameter, the usual
rule is to make the area of the screw cir-
cle proportional to that of the immersed
midship section. M. de Lome states
that the most favorable proportion, for
good ships, is ± ; but considering the in-
creased coefficient of resistance which he
had allowed for his vessel, he fixed the

diameter of his screw at 9 meters, which

gave a proportion to the area of ;— | or

loo

In English steamers, the propor-

2.65'

tion varies a great deal, but it may gen-

1 1

erally be taken as from ^— - to 5— g. M.

m . o o . o

de Lome's screw was very nearly three-
fifths the maximum diameter of the bal-
loon, and, in default of any experience
to the contrary, this proportion may be
retained.

In order to calculate the velocity of ro-
tation, it is necessary to estimate the
amount of slip. In M. de Lome's trial,
the pitch of the screw was 8 meters, the
number of revolutions 27-J- per minute,
and the speed of the balloon 169.2
meters per minute. Hence the advance
of the vessel for each revolution was 6.15

meters, giving a " slip ratio " of , or

about 23 per cent.

M. de Lome's pitch was eight- ninths
the diameter, but this is unusually fine,
the general ratio varying from 1 to 1.5.
With steam power, no doubt the pitch
might be advantageously increased, but
in the absence of experience it may not
be advisable to depart too widely from
what has been done, and the ratio may
be put = l. M. de Lome originally pro-
posed this pitch, and why it was reduced
he does not explain.

Calculating on the above slip and
pitch, if n= revolutions per minute —

?l =

78 v

diameter of screw'
or, reverting to equation IV. —

which will give the number of revolu-
tions for the maximum speed of any
diameter of balloon on the data before
named.

Returning to equation IV., the ex-
pression shows that a certain magnitude
of balloon is necessary to obtain any
power of navigation, and that the capa-
bility will increase with the diameter.
Some different sizes may be calculated
in order to illustrate the application of
the formulae, and the results are shown
in the following Table.

TIIK PROBLEM OF AERIAL NAVIGATION.

Dirigiblk Balloons.

As calculated from data in accordance with the actual trials of Messrs. Qiffard and Dupuy
de Lome, combined with the results of the most recent improvements in steam motors.

Maximum diameter

Feet.

110

Feet.

147

Feet.

183

Feet.

75
275

Feet.

100

367

Total ascending force

lbs.
2,970
2,370
600

lbs.
7,040
4,220

2,820

lbs.

13,750

6,600

7,150

lbs.
46,400
14,850
31,550

lbs.

110,000

26,400

83,600

140

370

}

Weight disposable for cargo, after
allowing for fuel and water

Cwt.

Cwt.
32

Tons.

Tons.
18*

Maximum speed through the air,

18
76

Diameter of screw, in feet

Revolutions per minute for maximum

The smallest size of balloon that
would be of any use would be about 30
feet in diameter. This would carry an
engine of about 3 HP., giving a maxi-
mum speed of 12 miles an hour. The
weight available for cargo would be,
however, only about sufficient for one
person.

Next take 40 feet diameter, the size of
M. Giffard's balloon. This would carry
12 HP., would attain 17 miles an hour,
and would carry 12^ cwt. of cargo. M.
Giffard's engine was only 3 HP., but his
balloon was inflated with common coal
gas instead of hydrogen, and was there-
fore deficient in ascending force. The
power he had ought to have produced
a speed of 10 miles an hour ; the reason
bis result fell so much short of this was
the small size of the screw, which was
only about one-fifth the proper area, and
was therefore quite unable to utilize
beneficially the power employed. It is
well known, in water navigation, that the
loss by slip increases largely when the
screw is unduly reduced in size.

The next example is about the size of
M. de Lome's balloon, 50 feet diameter,
and the calculation shows what it would
have done had he used more favorable
proportions, and availed himself of the
modern steam power. He could at this
rate, have carried an engine of 32 HP.,
which would have turned his screw three

times as fast, and would have given him,
with the higher pitch, a speed of 20 miles
an hour.

By increasing the diameter to 75 feet,
the balloon would have a velocity of 25
miles per hour. Even 100 feet diameter
would not be an unreasonable magnitude,
and this, keeping the same proportion of
power to weight, would give a speed
through the air approaching 30 miles an
hour, and would have 18 \ tons dispos-
able for cargo.

These are no doubt startling results,
but they arise legitimately from the data
now in existence, and it will be seen
that their significance, in giving a new
aspect to the problem of aerial naviga-
tion, is largely due to the mechanical im-
provements effected in quite recent times.
Before the invention of the screw pro-
peller, there were no feasible means
whatever of attacking the problem ; and
even after Giffard and Dupuy de Lome
had shovvn how the screw might be ap-
plied, it was not till within the last year
or two that the weight of the motor and
its stores had been so reduced as to give
any hopeful prospect of useful results.
That there is now such a prospect, so far
as mechanical reasoning can justify it,
hardly admits of a doubt.

PRACTICAL CONSIDERATIONS.

It only now remains to inquire into

VAN NOSTRAND'S ENGINEERING MAGAZINE.

some of the more important considera-
tions bearing on the question in a prac-
tical point of view. And these divide
themselves into two classes : — first, as to
the construction of the balloon, and sec-
ondly, as to its use.

In regard to the first head, the provi-
sion of the gas, and its preservation in
an envelope that shall be at once light,
impervious, and strong, are conditions
of ordinary study for balloons generally.
M. Giffard devoted much attention to
them, and the large captive balloons he
constructed were filled with hydrogen at
a very moderate cost, which was retained
for a long period with scarcely any loss.
M. de Lome also considered his arrange-
ments in this respect satisfactory. All
other matters of a strictly aeronautical
character, may safely be left to the many
eminent experts in the art.

But for this purpose an unusual form
of balloon is necessary, and important
questions arise as to its stability. M.
de Lome, with his great experience in
analogous questions in naval architect-
ure, saw the importance of this point,
and took great pains to investigate the
problem. His reasonings may be found
fully detailed in the " Comptes Bend us,"
and it will suffice here to say that he not
only determined the stability theoretical-
ly, but found his expectations fully
borne out by the result of his trial. M.
Giffard before him had had doubts on
the subject, but adds that his experi-
ment had fully reassured him, and had
shown that the use of an elongated bal-
loon was in all respects the most ad-
vantageous possible.

As an instance of the care bestowed by
M. de Lome on the mechanical design,
one contrivance is worth mention. As a
balloon rises or falls, the contained gas
expands or contracts in bulk, by reason
of the variation in the atmospheric press-
ure. With the ordinary globular bal-
loon the envelope is only partially filled
at starting, and room is left in the lower
part for the expansion. But with a nav-
igable balloon it is desirable that the ex-
ternal shape should be maintained
smooth and unalterated at all elevations.
This M. de Lome accomplished by tak-
ing advantage of a suggestion made by
General Meusnier at the end of the last
century, namely, by putting inside the
balloon an air pocket, or reservoir, the

expansion or contraction of which would
compensate for any difference in the
bulk of the gas caused either by varia-
tion in height or by loss in escape or
leakage. This internal vessel was con-
trollable from the car, and it might be
given a more extended application in
regulating the vertical movements of the
balloon generally. M. de Lome states
that the behavior of his balloon, not only
as to stability, but as to ease of manage-
ment, was all that could be desired.

In regard to the propelling apparatus,
the design of a suitable steam motor
would be only a simple task to mechani-
cal engineers accustomed to work of the
kind. The construction of the propeller
itself would involve more difficulty, owing
to the absence of experience on any large
scale of power and speed ; for in large
balloons it must be of considerable size.
M. de Lome made one of 30 feet, which
appears to have answered very well for
his small speeds ; but with the higher
velocities the thrust would be, of course,
increased. The 30-feet screw, when pro-
pelling at 20 miles an hour, would have
to convey a thrust of about 360 lbs., and
this would require a corresponding in-
crease of strength. For the largest bal-
loon in the table the screw must be 60
feet diameter (about the usual size of a
windmill) and it would convey a thrust
of about 3,000 lbs. The design and con-
struction of such screws, so as to make
them combine the necessary strength
with the necessary lightness, would no
doubt call for considerable mechanical
skill.

There is also another point requiring
attention, in regard to the position of
the screw. To maintain perfect stability
during the propulsion through the air,
the propelling force ought to act in a
horizontal line with the center of all the
resistances, which would be a little be-
low the line of the axis. When it is
placed lower, there results a tendency to
throw the balloon a little out of level.
M. de Lome calculated this, and found
the deflection was, in his case, less than
a degree, which was inappreciable. At
higher speeds it would be increased, and
probably, with a 100-feet balloon, pro-
pelled at 30 miles an hour, it might
amount to several degrees, and its effect
would require correction in some way.

An arrangement must also be made to

THE PROBLEM OF AERIAL NAVIGATION.

meet the disturbing effect of the loss of
weight by the consumption of fuel and
water, without wasting the gas ; prob-
ably M. de Lome's internal pocket
might be made useful for this purpose
also.

These are, however, after all, only mat-
ters of practical mechanics, and one can-
not doubt the ability of engineers of the
present age to deal with them satisfac-
torily if the requirement should arise.
On the ground, therefore, of practical
construction, there appears no reason to
doubt the feasibility of carrying out the
principles arrived at by theoretical con-
siderations. It is possible that by prac-
tical necessities the estimated weights or
resistances might be somewhat increased ;
but there is considerable margin for this,
and it must be borne in mind that all the
data have been taken on things as they
are. "When the whole arrangement came
to be carefully studied and tried, it is
certain that improvements would take
place, and what might be lost in some
particulars would probably be recouped
in others.

But, assuming that dirigible balloons
can be constructed, it is desirable fur-
ther to inquire what practical considera-
tions might affect their use.

It is hardly necessary to say that the
introduction of a locomotive machine
which would transport a large number
of people through the air, in any direc-
tion required, at the rate of 20 or 30
miles an hour, would be a remarkable
novelty, and would offer many advan-
tages. Comparing it with ships and
boats, it would be far swifter, much less
expensive in first outlay and cost of
working, would require no harbors,
would produce no sea-sickness, and
would escape the greatest dangers in-
herent in water navigation. As a means
of land transport, it would be quicker
than common road traveling, and would
compare fairly with the ordinary speed
on railways, while it would dispense with
the costly provisions requisite for both
these modes of getting over the ground,
and would be free from the multitude of
liabilities to accident attending them.

But it may naturally be objected that
such a mode of locomotion would have
peculiar dangers of its own. No doubt
balloons have hitherto been very subject
to accidents, and the bare idea of any-

thing going wrong at a height of thous-
ands of feet above the earth is very ap-
palling. But much of this impression
will vanish before common -sense reason-
; ing. It must always be borne in mind
that for the purpose of locomotion there
would be no reason for ascending high
into the air ; it would only be necessary
to keep at a sufficient altitude to clear
terrestrial impediments, and this would
not only do away with much of • the ter-
ror of the idea, but would greatly in-
1 crease the probability of a safe escape
from accidents of whatever kind.

It is worth while to consider in what
direction danger might, in extreme cases,
lie. The loss of gas, by rupture of the
envelope or otherwise, is a remote possi-
bility ; but the experience of many actual
cases has proved that the resistance of
the air to the large surface exposed has
sufficed to prevent any rapid fall. Spe-
cial measures might be easily provided,
and at low elevations over land no seri-
ous catastrophe need be feared on this
ground. In crossing over water precau-
tions would still be possible, and the
case, would not be so hopeless as in many
marine casualties. The danger of fire,
if properly guarded against, need not be
greater than in a ship at sea. Indeed,
M. Giffard, who has tried the experi-
ment, expressly states that the idea of
such danger is quite an illusion .

The accidents that arise to ordinary
i balloons almost always occur in the de-
scent, which, if the wind is high, requires
i great care and skillful management. In
! this case the propelling power would be
i most especially useful ; the aeronaut
! could choose his place of landing with
precision, and by turning his head to
the wind he could avoid the dragging
which is so dangerous, and which has so
often brought a fatal termination to bal-
loon voyages.

On the whole there can be no good rea-
son to believe that the danger would be
more formidable with this than with
other kinds of locomotion. One cannot
ignore the frightful casualties that so
frequently now occur in land, river, and
sea traffic ; and when it is considered
how many of their causes would be ab-
sent in the free paths of the air, one may
even venture to assert that balloons
would be the safest, as well as the pleas-
antest, mode of traveling.

van nostkand's engineering magazine.

As a set-off against this, however,
there is one great disadvantage attend-
ing aerial locomotion, namely the un-
certainty it must always be liable to, in
consequence of the effect of the wind.
The course of any floating vessel is nat-
urally affected by the general motion of
the medium in which she floats. With
water the currents may amount to a few
miles an hour; with air they will be
much more, so much as seriously to in-
terfere with the locomotive capabilities
of the balloon.

According to data gathered from the
meteorological reports of Greenwich Ob-
servatory for the year 1877, it appears
that —

During 17 days in the year
mean velocity of
wind was between
" 103 days in the year
mean velocity of
wind was between
" 127 days in the year
mean velocity of
wind was between.
75 days in the year
mean velocity of
wind was between .
" 29 days in the year
mean velocity of
wind was between.
10 days in the year
mean velocity of
wind was between.

Miles per hour.

the

the
0 and 5

the

the
.... 5 " 10

the

the
....10 " 15

the

the
....15 " 20

the

...20 " 25

the

...25 " 30

361
3

days in the year the
mean velocity of the

wind was between

day in the year the
mean velocity of the
wind was between. . . .

365

The mean over the whole year was 13
miles an hour. At higher levels these
velocities are exceeded ; but, as has been
before stated, if balloons were used for
the purposes of locomotion, there would
be no necessity for them to travel at any
great altitude.

Now the course of a navigable balloon
will be, like that of a steamer in a tide-
way, a compound of its own independent
velocity with that of the general motion
of the surrounding medium. This can
easily be calculated by the ordinary rules
of navigation, and the following table
shows the manner in which the composi-
tion of the two motions will influence the

locomotive capability of the moving
body. It is formed on the assumption
that an independent speed of 30 miles
an hour might be given to the balloon,
and that the wind blows with velocities
varying from 0 to 50 miles an hour. The
wind is assumed due north, but the re-
lations will be the same for any other
direction.

Aerial Navigation. ■

Table showing the speed, in miles per hour,
that could be commanded on any proposed
course, by a dirigible balloon having an inde-
pendent motion through the air of 30 miles
per hour. Wind supposed due north, blowing
with velocities varying from 0 to 50 miles per
hour.

Proposed Course.

Velocity
of wind.

Calm

u
o

30
27
25
20
16
9

30
35
40
45
50
55
60
65
70
75
80

The practical result of this would be
as follows :

(1.) In storms and gales, say exceed-
ing 40 miles an hour, it would not be
prudent for the balloon to travel at all.
Ships only sail " wind and weather per
mitting," and balloons must submit to
the same restriction.

(2.) In high winds, say from 30 to 40
miles an hour, it could only go in a
course generally corresponding with that
of the wind ; but it would still have a
considerable range of direction and a
high velocity, and, what is of the great-
est importance, it would have the power
of steering, and would be able to com-
mand its descent at any time, and in any
place, without danger.

(3.) In light and moderate winds, un-
der 30 miles an hour, which the Green-
wich observations record to prevail all
the year with the exception of a few
days, it could travel in any direction,

AS TO THE FUTURE OF ELECTRIC RAILWAYS.

the speed varying from 5 to nearly 60
miles an hour.

It must also be added that with con-
trary winds the voyages must be neces- ,
s.irily short distances at a time, from the
impossibility of carrying large stores of
fuel and water to keep up the full power
lor any long period. But with favorable
winds, such as* the trades, almost any
distance might be run, as the use of the
engine would be limited to what was ne-
cessary for steering purposes.

These conditions would no doubt
render aerial navigation unsuitable for
traffic that requires regular and punctual
transit, and would, therefore, much limit
its commercial value. It could never,
for such purposes, compete with rail-
ways, or lines of river or sea navigation.
But still a great variety of cases exist
where its peculiar advantages would tell
in practical use ; and probably, if such
a means of locomotion were once intro-
duced, increased employment for it
would soon arise.

SUMMARY.

The foregoing investigation appears
to warrant the following conclusions.

1. The problem of aerial navigation by
balloons is one as perfectly amenable to
mechanical investigation as that of
aquatic navigation by floating vessels ;
and its successful solution involves noth-
ing unreasonable, or inconsistent with
the teachings of mechanical science.

2. It has been fully established by ex-
periment that it is possible to design and
construct a balloon which shall possess
the conditions necessary for aerial navi-
gation, i. e., which shall have a form of
small resistance, shall be stable and easy
to manage, and, if driven through the

air, shall be capable of steering by a
proper obedience to the rudder.

3. If, by a power carried with the bal-
loon, surfaces of sufficient area can be
made to act against the surrounding air,
the reaction will propel the balloon
through the air in an opposite direction.

4. The modern invention of the screw
propeller furnishes a means of applying
power, in this way, to effect the propul-
sion ; and the suitability and efficacy of
such means have been shown by actual
trial.

5. Sufficient data exist to enable an
approximate estimate to be made of the
power necessary to propel such a balloon
with any given velocity through the air.

6. The recent great reduction in the
weight of steam motors has rendered it
possible to carry with the balloon an
amount of power sufficient to produce
moderately high speeds, say 20 or 30
miles an hour through the air ; and by
taking advantage of other recent improve-
ments it would also be possible to carry
a moderate supply of fuel and water for
the working.

7. The practical difficulties in the way
are only such as naturally arise in the
extension of former successful trials ;
and such as may reasonably be expected
to give way before skill and experience.

8. The practical utility of aerial loco-
motion must always be considerably re-
stricted by the effect of the wind, which
it is impossible for any flying body to
evade. But still, such a system would
have peculiar advantages of its own ;
and on the whole, dirigible balloons may
form a feasible and useful ^ddition to the
present means of transport, and are,
therefore, worthy the attention of the

AS TO THE FUTURE OF ELECTRIC RAILWAYS.

From "The Builder."

The application of electricity to loco-
motion is a subject on the exhaustive
knowledge of which so much of the fu-
ture welfare of the human race depends,
that it is desirable to refer to those state-
ments by Professor Ayrton on the sub-
ject, some of which are to be found in our
columns (ante, p. 384). Nor is our ob-
ject in thus doing so much either to sup-

port or combat the opinions of the lec-
turer, as to bring forward some of those
considerations which the practical knowl-
edge of our railway system from its very
cradle have rendered more familiar to the
engineer than to the electrician.

Professor Ayrton has not omitted to
point ou"} that the work done in the mov-
ing of the locomotive engines forms a

van nostkand's engineeking magazine.

very serious part of the whole work done
by our railways. This, no doubt, is so ;
and that it is so to a greater extent than
has been as yet estimated will be seen by
what we have to remark.

That the engines on the railways of
the United Kingdom travel a much longer
distance than the 222 millions of train
miles of which the Board of Trade returns
yield us the sum, there is, of course, no
doubt. In some of the accounts of the
companies, the mileage of engines is, or
rather was, returned as a separate item
from the train mileage ; but we find no
information on this score in the " Rail-
way Returns " or in the " Index to our
Railway System " at present. We are,
however, in possession of two sources of
information on this subject, to which it
may be of service now to direct attention.
One of these is the Report on the Rail-
ways of New South Wales, which, as
published at Sidney, is not by any means
so well known in this country as ought
to be the case. The other is a series of
elaborate tables of the working elements
of the Richmond and Danville Railroad
Company, which we o»we to the courtesy
of the general superintendent of that line.

On the New South Wales Railways in
1876 (the latest year for which we have
a report at hand), the total number of
engines and tenders was 101, — 51 being
for the passenger, and 50 for the goods
traffic. The passenger engines weighed
a little over 38 tons, and the goods en-
gines a little over 49 tons each, the weight
of the tender being included. The car-
riages forming the passenger stock
weighed a little over 6 tons 1 cwt, on the
average, and were 344 in number. The
goods vehicles were 3,198, and weighed,
on an average, 4 tons 16 cwt. The gross
mileage of the engines in the year was
2,160,242 miles, of which 993,522 were
run by the passenger engines. .

The Government Commissioner for
Railways in New South Wales in that
year, Mr. John Rae, to whose conscien-
tious appreciation of the duties of his po-
sition we owe the above data, has gone a
step farther in his tables, and has given
us not only the materials for calculation,
but the outcome of very minute compu-
tations. It is not necessary to add very
much labor to the published tables to
come to the following results :

For the passenger traffic on all the New

South Wales lines, in the year 1876, the
proportionate weights of engines, vehi-
cles and loads were: —

Engines 51.3

Vehicles 45.3

Loads 3.4

100

For the merchandise traffic, the corre-
sponding proportions were :

Engines 34.8

Vehicles 42.4

Loads 22.8

100

The value of statistical information of
this kind becomes very great when we
enter into such questions as that of the
economy possible to be effected by elec-
tric power. From 35 to 51 per cent, of
the gross work done on these railways
consisted in moving the locomotives
themselves. But, in addition to this, the
disadvantage at which the locomotive
works is shown by the difference of the
formulae used to express the resistance
to the carriage and to the entire train.
For a train consisting of an engine and
tender weighing 50 tons, and 100 tons of
carriages, the total resistance, at thirty
miles an hour on the level, is 3,000 lbs.
But the resistance to the carriages alone
is only 1,328 lbs. Thus, it is not only
in the weight to be moved, but also in
the mode of moving the weight, that
the locomotive is so costly, that an econ-
omy of 56 per cent, would be secured by
dispensing with its use. How much of
the proportions of 45 and 42 per cent,
of the gross load that is formed by the
vehicles is due to the extra strength re-
quired for the resistance to locomotive
energy is not so obvious.

Turning now to the tables kindly fur-
nished by Mr. T. M. R. Talcott, the gen-
eral superintendent of the Richmond and
Danville Railroad Company, we have
somewhat different results, although the
difference may probably be accounted for
by the lower speed at which the traffic is
usually carried on in the United States,
as compared to that to which we are ac-
customed, and by the larger volume of
traffic. On the average of the three years,
1875, 1876, and 1877, the proportionate
weights were as follow : —

\- TO I'll 1 : FUTURE OF ELECTRIC RAILWAYS.

For passenger traffic

Engines .
Vehicles.
Loads. . .

32.80
61.58

100

For merchandise traffic —

Engines 15.86

Vehicles 51.98

Loads 83.17

100

As tlit- Now South Wales lines are in
an early stage of development, it may be
I hat we have here two extreme
-, within the limits of which the pro-
portionate weights will be found to
range on different lines. Roughly aver-
aging the above, we find that the weight
of the locomotives is abont 35 per cent.,
that of the vehicles -49 per cent., and that
of the load 16 per cent, of the total
»ht moved.

On this view, as far as the mere ques-
tion of the weight of the locomotive is
rded, it may be doubtful howT far the
loss of power by electric leakage will
serve to counterbalance any economy
effected by the abandonment of the en-
gines. But the question of the diminu-
tion in the weight of the vehicles has to
be borne in mind. As to that, we are
not prepared at the present moment to
offer a decided opinion. But there can
be little doubt that the important item
of capital outlay would be enormously
reduced, both by the diminution in the
strength of the permanent way and of
the works of art that would be neces-
sary to carry the traffic, if the heavy en-
gines were abandoned, and in the much
greater steepness of the inclines which
it would be not only possible, but easy,
to work, under those conditions.

We are, further, in possession of in-
formation derived from an experience
which 'is now almost forgotten, but
which bears very directly on this ques-
tion. It is now some thirty-six years
since Mr. Robert Stephenson designed
the mode of working the Blackwall Rail-
way by stationary power. Mechanically
regarded, the plan was a success ; and a
financial result was also admirable. But
a practical difficulty arose from the con-
stant twisting and breaking of the rope.
And what rendered this so formidable as
to lead to the abandonment of the sys-
Vol. XXVII.— No. 1—2.

fcem was fche fact, that on the fracture <>f

the rope fche whole traffic of the railway,
on both lines, was brought to a stand-
still.

But the most interesting part of this
experience is this. The cost p<t train

mile was Is. 6Jd.; the trains, however,
being much Lighter than those which on
fche railways of the United Kingdom now
cost an average of 2s. lid. per mile. Of
this cost, however, by far the greater
part was incurred in moving the ma-
chinery and the rope. Out of 324 indi-
cated horse power, it was found that 251
horse power wras thus expended ; so that
only 63 horse power, or under 20 per
cent, of the whole, was employed in the
direct traction of the vehicles and load.
The cost, notwithstanding, works out
as low as 0.187d. per ton per mile, which
we make to be 10 per cent, lower than
the average cost of propelling a ton for a
mile on the railways of the United King-
dom in 1879. But as the traction of the
load and vehicles only absorbed 20 per
cent, of this power, we get a cost, for
that part of the duty alone, of 0.038d.
per ton per mile, or less than one-fifth
of the cost of the railway power of to-
day. We do not insist too much on the
accuracy of the comparison, because the
cost now includes some 30 per cent, in
the form of traffic expenses, which were
not so heavy on the Blackwall line.
Still, on the rough statement that, (1)
stationary power is somewhat less costly
than locomotive power, even under cir-
cumstances unfavorable for the former,
and (2) that these circumstances may be
so unfavorable as to increase the power
required for the traction of load and
vehicle alone from 63 to 324 horse power,
we think it is tolerably clear that any
mode of using stationary power, which
can draw a train , saving the weight of
the engine, and applying its force in
such a manner as not to lose more than
30 or 40 per cent, between the motor and
the work, has an immeasurable future
before it.

A large Lacustrine canoe has been
found at Bex, Switzerland, in a fine
state of preservation. Bex is 4000
feet above the sea level, and near-
ly 3000 feet above the Valley of the
Rhone.

VAN" NOSTRAND'S ENGINEERING MAGAZINE.

THE BASIN AND KEGIMEN OF THE MISSISSIPPI RIVER.*

By PROF. C. M. WOODWARD.

The Upper Mississippi unites with the
Missouri River about twenty miles above
St. Louis, so that the Mississippi, as it
rolls by the city, contains only the waters
of those two streams. The basin of the
Missouri River includes an area of 518,-
000 square miles ; that of the Upper
Mississippi about 169,000 square miles ;
hence the drainage of 687,000 square
miles of the earth's surface forms the
river at St. Louis.

The great extent of this joint basin is
better appreciated. when it is compared
with other areas well known. It is
eighty-eight times as large as the State
of Massachusetts, or equal to the com-
bined areas of England, Scotland, Wales,
Ireland, France, Spain, Portugal, Hol-
land, Belgium, Switzerland and Italy.
Again, it is equal to the sum of the areas
of the basins of the Vistula, Oder, Elbe,
Rhine, Seine, Loire,* Garonne, Douro,
Tagus, Ebro, Guadiana, Rhone, Po and
the Danube. It is however probable that
the volume of water discharged is not
proportionately great.

The basin of the Upper Mississippi is
wholly devoid of mountains, though the
country is well wooded and abundantly
supplied with lakes and streams. The
average annual rain fall is 35.2 inches.

The Missouri basin includes the east-
ern slope of the Rocky Mountains for a
length of about 800 miles. From these
mountains several large streams issue,
and flow for hundreds of miles across the
great barren plain with little increase of
size. "Comparatively little rain falls
upon the mountains and plains, and
hence the size of the main river is pro-
portionately small when the drainage
area alone is considered."! The average
annual rainfall in this basin is 20.9 inches,
and that of the two rivers combined is
24.4 inches. The river drainage is less
than one-fifth of this average.

The average discharge per second of
the Upper Mississippi is given as 105,000
cubic feet, and that of the Missouri as

Hence the discharge

* A History of the St. Louis Bridge, by C. M. Wood-
ward. St. Louis : G. J. Jones & Co.
t Humphrey's and Abbot's Mississippi River.

120,000 cubic feet
of the river at St. Louis is 225,000 cubic
feet per second or 7,080,000,000,000 cubic
feet per year. The maximum discharge
must be at least four times this average.

At the mouth of the Missouri, the Mis-
sissippi takes on its peculiar character of
a deep and boiling torrent. Its width is
increased but not so much as its depth.

The river is subject to great changes
both seasonal and irregular. The high-
est water is during the " June rise. "
(which may be a month or two early or
late), and low water is usually in Decem-
ber. The greatest range ever observed
at St. Louis between extreme high and
extreme low water is 41.39 feet, the high
water being that of 1844 when the water
was 7.58 feet above the city directrix.
The city directrix is the curbstone at the
foot of Market street, and marks the
height of the water in 1828 ; it serves as
the datum plane for all the city engineer-
ing at St. Louis. The bridge levels are
generally referred to the same line.
Thirty-four feet below the city directrix
is known as "low water."

The velocity of the current where it is
greatest, opposite, to St. Louis, varies
from 4 ft. per second (or 2f miles per
hour) at low water, to 12^- feet per sec-
ond (or 8^ miles per hour) at extreme
high water. The average slope of the
water surface is about 6 inches per mile
near St. Louis.

At all times the river water is turbid,
and when it is allowed to stand a few
hours a sediment is deposited ; but the
amount of matter held in suspension
varies greatly. The sediment consists of
finely divided vegetable and mineral mat-
ter gathered from tributaries through al-
luvial districts, and from the bed and
banks of the stream. In order to appre-
ciate the difficulties to be surmounted
in bridging the Mississippi at St. Louis,
it is necessary to clearly understand the
laws which appear to obtain in the action
of the river upon its banks and bed, and
so determine its power to transport sed-
imentary matter.

This " carrying power " has reference

THE BASIN AND REGIMEN OF THE M I-- I -M 1MM RIVER.

11)

not only bo the amount of sedimentary

matter it can hold in suspension but also
to tin.1 amount of materia] which under
the influence of the impulsive force or
momentum, of the water is driven along
in a more or less fluid state. The dis-
tinction here mule is one of degree rather
than of kind. Water moving slowly in
a smooth, regular channel, can carry
little mineral matter ; but, increase
its velocity and volume and it will sweep
along not only sand and mud, but gravel
and large pebbles. When from irregu-
larities in the bed of a stream, the body
of the river is full of whirlpool s— cross
and vertical currents — the action is anal-
agous to that of jets driven by high
pressure.

It appears that this transporting power
of a river depends upon : (1) The spe
citic gravity of the sediment, (2) the size
of the sedimentary particles ; (3) the rela-
tive or internal velocity of adjacent
masses of water ; (4) the depth of the
stream ; (5) the absolute velocity of the
stream.

1. Woody fiber and the tissue of vege-
etable cells, loam, clay, particles of lime-
stone, sand and gravel form the main
burden of the river. The specific gravity
varies from 1 to 3.

The specific gravity of the strictly sus-
pended matter is given as 1.9 by Hum-
phreys and Abbot.

2. The size of the particles is very im-
portant. The heaviest materials, if in a
finely-divided state, may be transported
by the running water in rivers. If the
particles are supposed to be similar in
shape, we easily see that their stability in
running water is less as they become
smaller. Their weight, and consequently
the resistance which they offer to being
raised or pushed along by currents, varies
as the cube of any one of their dimen-
sions, as, for instance their thickness ;
while the force to which they are ex
posed (the pressure or impact of the
waters upon their surface) varies only as
the square of the thickness. For exam-
ple take two similar blocks of granite, or
two grains of sand, the larger of which is
three times as thick as the smaller; the
weight and therefore the friction of one
is twenty-seven times that of the other ;
while its surface, and hence the force
with which water would press upon or
strike it, is only nine times as great. It

is evident that the smaller particles might
be transported or pushed along, while the

larger would stand unmoved. It follows
that, for a given current of water, there

is a point of fineness for each substance

at which the particles become transport-
able. As a consequence we should ex-
pect in a diminishing river current to
find the larger and denser particles left
behind first, the smaller and lighter next,
and so on, the finest and lightest only
being deposited where the water is sta-
tionary.

3. In a stream full of whirlpools and
boils (or vertical currents in opposite di-
rections) the water is intermittently im-
pinging upon the bed and banks. These
currents not only prevent the deposit of
what would otherwise come to rest on the
river bottom, but when not fully loaded
with sedimentary material, they seize
upon all within their reach and carry it
along. So far as velocity in the direc-
tion of the axis of the stream is con-
cerned, the greatest "difference of veloc-
ity '' in adjacent water layers, or masses,
is found near the bed and banks of the
stream ; but where cross and vertical
currents exist, the resultant difference in
velocity is likely to be greatest, where the
onward flow is greatest.

4. The modifying effect of depth on
the power to transport solid matter in a
sediment-bearing stream is shown in two
ways :

In the first place as the depth increas-
es, the internal relative motion of adja-
cent layers is diminished (" still waters
run deep," and conversely) ; this alone
lessens the transporting power. In the
second place, the relative motions of a
deep stream are powerful, and slowly
moving masses of water produce great
inequalities of pressure on the materials
of the bed. These unequal pressures suf-
fice to keep the loose material on the
bottom in constant motion, thus increas-
ing the transportation. A paragraph in
Mr. Elds' report of Miy, 18GS, is so per-
tinent that I quote it here. " I had occa-
sion," he says, u to examine the bottom
of the Mississippi, below Cairo, during
the flood of 1851, and at sixty-five feet
below the surface I found the bed of the
river, for at least three feet in depth, a
moving mass, and so unstable that, in
endeavoring to find a footing on it be-
neath my bell,my feet penetrated through

van nosteand's engineeeing magazine.

it until I could feel, although standing
.erect, the sand rushing past iny hands,
driven by a current apparently as rapid
as that at the surface. I could discover
the sand in motion at least two feet be-
low the surface of the bottom, and mov-
ing with a velocity diminishing in pro-
portion to its depth." At Carrollton,
gravel, sand and earthy matter were
found moving along the bottom at a
depth of about 100 feet by Professor
Forshey. It is obvious that increase of
depth diminishes rather than increases
the " suspending " power per unit of
volume, though it adds largely to the
motive force of the stream.

The absolute velocity of the water is
of course a very important matter, both
from the momentum with which it strikes
all obstacles, and from the fact that in-
crease of absolute velocity always in-
volves increase of relative motion. With
a given channel, depth of stream, nature
of sediment, there is a maximum load for
each velocity, and the load increases as
the velocity increases, though the law is
not exactly known. The practical limit
to the power of waier to hold matter
heavier than itself in suspension suggests
that the solid particles afford each other
a sort of protection from the impulsive
force of the water, and that the amount
of this protection increases as the num-
ber of particles in suspension increases,
and that at a certain point the protec-
tion is so efficient that the water is un-
able to prevent their fall. This protec-
tion is of course mutual among the par-
ticles. Thus, if we suppose several grains
in contact and in a row, we see that the
efficiency of the force is much less than
with a single particle, as the surface of
action remains the same, while the force
to be overcome is increased. As the ki-
netic energy of the water is proportional
to the square of its velocity, it is prob-
able that the law referred to above would
prove that the carrying power of a river
is, other things being equal, proportional
to the square of its velocity.

These main principles, derived partly
by theory, and partly by observation, are
well confirmed by the behavior of the
Mississippi at St. Louis. At " low water "
the water is least turbid, the velocity is
small, the stream shallow and confined
to the main channel. It can carry but
little solid matter, and it finds its load in

the deposits made during the subsidence
of the last flood. This is comparatively
heavy material, and settles readily when
the water is stationary. When from any
cause a rise takes place, the increasing
tide seizes upon the lighest and finest
materials first, and it is noticed that the
suspended matter in samples of water at
such times settles slowly and with
great difficulty. But the demand of a
flood is not easily satisfied. If the water
enter the stream comparatively clear (like
the Upper Mississippi), it is much under-
charged and quickly attacks the old de-
posits along the river bed, and if the
flood is great, it even scours out and
carries away sand bars and islands. It is
generally true in the Mississippi that
changes in level of the surface are accom-
panied by contrary changes in the bed —
i. e., as the surface rises, the bed falls
under the erosive action of the flood, and
as the surface falls, the bed rises by de-
posit. The heavier materials are trans-
ported with far less than the mean veloc-
ity of the stream, and as the flood begins
to subside, they are left behind in the
form of new bars and alluvial deposits to
form new islands.

A flood from the Missouri invariably
brings great quantities of matter into the
Mississippi ; and if at the time the Upper
Mississijypi is low, the result on the re-
turn of the river to its normal flow is a
large increase of mud and bars, which
under the action of a joint flood, or one
from the Mississippi alone, disappears.
In this way the bed of the stream is con-
tinually changing : but every change is
towards the Gulf of Mexico, into which
not only the lighter suspended matter
finds its way, but ultimately the sand
bars as well.

The depth of scour of the river is
sometimes very great. An obstacle in
mid-channel, like the wreck of a boat, the
pier of a bridge, or a thick gorge of ice
may serve to give to the current a new
direction and increased velocity, forcing
it far below the normal bed of the river.
In 1854 Mr. James H. Morley, chief en-
gineer of the Iron Mountain Railway,
took soundings through the ice across
the Mississippi near the site of the pres-
ent bridge. He found a depth of 78 feet,
when the river was only 10 feet above
low water. The " line of scour " was
thus shown to be at least 68 feet below

THE BASIN AND REGIMEN OF THE MISSISSIPPI RIVER.

low water, instead of 30 feet below, as
was assumed by Mr. Boomer's conven-
tion of engineers in 18(57. Soundings
made in 1876 off the east abutment of the
bridge where, when the abutment was
constructed, the water was not more than
15 or 20 feet deep, showed a depth of
nearly 100 feet. The materials of which
the bed of the river at St. Louis is com-
posed were seen by borings, and later by
the excavation under the bridge piers, to
be the heavier debris of river floods.
Even the bed rock when laid bare, was
smooth and water worn. It is clear that
either the mighty river had at one time
its normal bed on the rock, or else it has
in ages past during its countless floods,
again and again scoured down to the
rock itself. In the light of these facts,
he would be a rash engineer indeed who
should place any reliance upon the un-
certain footing of the river bottom as a
support for the foundations of his
bridge.

The river ordinarily freezes over in
winter. The ice coating is however
generally composed of huge irregular
fragments of ice from the North. No
sooner does the cold weather set in than
the river is full of cakes of ice. Under
the influence of intense cold, the cakes
freeze together and form large ice
fields. These, in some narrow pass or
across the head of an island, gorge to-
gether, become stationary, and unite in-
to a strong bridge of ice. The surface
of the river above is soon crowded full
of ice, and the river is closed. During
the formation of an ice gorge, large cakes
of ice are carried by the current under-
neath the surface layers to such an ex-
tent that the gorge is, at times, a solid
mass of 20 feet or more in thickness.
The scouring action of the water under
such gorges is obvious. Since the erec-
tion of the bridge the piers have helped
to form an ice gorge' above it, leaving the
water clear below. This has proved of
great value to the navigation of the low-
er river, and has caused very deep water
between and above the piers. Founda-
tions less deep and strong would have
been exposed to great dauger.

River ice is regarded as very treacher-
ous. Previous to the construction of the
bridge, the river would occasionally in
mid-winter be closed to boats and teams
for days together ; sometimes the most

daring footman could not cross. At such
times when all communication with the
East was suspended, when anxious trav-
elers were visible on the other shore, the
people of St. Louis earnestly prayed for
a bridge which should put them beyond
all danger of an " ice blockade.'' The
river has been known to close early in
December and remain closed till the lat-
ter part of February. After freezing
over the water usually rises a few feet,
from the action of the ice gorge.

There is something almost sublime m
the immense volume and apparently irre-
sistible power of this great river. The
ease with which it devours island after
island, and forms for itself a new chan-
nel ; the wTild deluge of waters with
which, without apparent loss of volume,
it covers thousands of miles of fertile
fields ; and the unequaled strength and
depth of the current, — suggest a power
so far beyond human control as to seem
almost lawless ; and yet nothing is more
certain than that, in all its moods and
phases, it is wholly obedient to nature's
law\s, and that the engineer who would
grapple with the problems involved in
the practical management of the Missis-
sippi must study and master those inflex-
ible ordinances.

Said Charles Ellet forty years ago :
" The power of this great river does not
prohibit any attempt to restrain, to force,
or to change its current ; on the con-
trary, it may be almost wholly subject to
the control of art . Apparently, it varies
its depth, alters its direction, reduces or
increases its width, with regard only to
its boundless power ; but these move-
ments are all made in obedience to cer-
tain laws, uniform and universal in their
action, to the rule of which it is as com-
pletely subject as any other effect in na-
ture to the cause by which it is produced.
To govern it the labor of man must be
applied with a knowledge of the influ-
ences which it recognizes ; and that
power which renders it apparently so dif-
ficult to restrain may then be made the
means of its subjection."

While Ellet thus wrote, James B. Eads
was studying the habits of the river from
the deck of a Mississippi steamboat, or
on the bed of the river under a diving-
bell. Over thirty years later, after an
intimate acquaintance with the river for
nearly forty years, Mr. Eads eloquently

TAN WOSTKAND'S ENGIJtfEEKING MAGAZINE.

gave utterance to the same thought :
"My experience of this current has
taught me that eternal vigilance is the
price of safety, and constant watchful-
ness is one of the first requisites to in-
sure success, almost as much as knowl-
edge and experience. To the superficial
observer, this stream seems to override
old established theories, and to set at
naught the apparently best devised
schemes of science. But yet there moves
no grain of sand through its devious
channel, in its course to the sea, that is
not governed by laws more fixed than
any there were known to the code of the
Medes and Persians. No giant tree
standing on its banks bows its stately
head beneath these dark waters, except
in obedience to laws which have been
created in the goodness and wisdom of
our Heavenly Father to govern the con-
ditions of matter at rest and in motion.

"It was necessary for this young engi-
neer* to master these laws before he dare
attempt to plant one of these stately
piers. Once assured by careful study,
patient experiment and close observation
that he was applying those laws rightly
to accomplish his end, the vagaries of
the stream were to him as easily compre-
hended, and as simple as the ordinary
phenomena of every-day life. No half-
way knowledge of the laws which control
this ceaseless tide, or govern the effects
of temperature, and the strength of ma-
terials, would suffice to accomplish what
he has done — to place these piers in this
river, and to spread across its turbulent
bosom, like gossamer threads, this beau-
tiful and strong iron structure, over
which the commerce of mighty States is
henceforth to roll with speed and
safety."

* Col. c.
Bridge.

Shaler Smith, Engineer of St. Charles

PILE FOUNDATIONS AND PILE-DRIVING FORMULAE.

From a Circular of the Office of Chief of Engineers,

The following correspondence respect-
ing pile foundations and pile-driving for-
mulae is communicated to the Corps of
Engineers.

The Chief of Engineers approves the
suggestions contained in Major Weitzel's
letter of the 4th of October, and desires
that the officers of the Corps will, at
their leisure, communicate to this office
any views they may have on the subject
of this correspondence, which he deems
of great practical importance, and also
the results of their experiences with pile
foundations.

He also desires that whenever an of-
ficer of the Corps has occasion to con-
struct a pile foundation, he will cause to
be kept an accurate record of the driving
of the piles, embracing the kind, and
average size and weight of the piles, the
weight and fall of the ram, and the pene
tr;ition at each blow, or at least at each
of the last (say five) blows, a copy of
which record he will send to this office
with a plan of the foundation, on which
is marked the estimated weight each pile

is to carry, and also a description of the
soil.

By command of Brig. Gen. Wright.

George H. Elliott.

Major of Engineers.

Abstract of a letter from Major G.
Weitzel, on the pile and grillage founda-
tion for the Martello tower at Proctors-
ville, La.:

The foundation was constructed in
1856 and 1857.

The site of the tower at Proctorsville,
as determined by actual borings was
found to have the following character,
viz.: For a depth of nine feet there was
mud mixed with sand, then followed a
layer of sand about five feet thick, then
a layer of sand mixed with clay from four
to six feet thick, and then followed fine
clay. Sometimes clay was met in small
quantities at the depth of six feet, as
well as small layers of shells. By drain-
ing the site the surface was lowered
about six inches.

The foundation piles were driven in a

PILE FOUNDATIONS AN1> PILE-DRIVING FORMULAE.

square of twenty piles on a Bide, four
from center to center. Twenty-four

omitted to leave room for fresh
water cisterns, and two extra ones were
driven to strengthen supposed weak
The total number at tirst driven
therefore 378. The piles were driven
to distances varying from 30 to 35 feet
below the surface, or from 10 to 15 feet
into the clay stratum. The average num-
ber of blows to a pile was 55, and mainly
bard driving. After all these piles were
driven, ten additional ones Avere driven
at different points to strengthen supposed
weak points. Each one of them required
over 100 blows to drive it.

Before beginning the foundation I
drove an experimental pile exactly in the
center of the site. It was 30 ft. long,
12±"xl2" at top and 111" X 11" at butt.
s sharpened to a bottom surface
about 4 inches square. Its head was
capped with a round iron ring. Its
weight was 1.611 pounds and the weight
of the hammer was 910 pounds. Its own
weight sank it 5' 4", and it required 64
blows to drive it 29' 6" deeper. The
fall of the hammer at the first blow was 6
feet, increasing each successive blow by
the amount of penetration, excepting the
last ten blows when the fall was regula-
ted to exactly 5 feet at each blow.

The penetrations in inches were as
follows :

12—12—16—11*-

^-H-'i-^.-n-

6—6-6J-— 6|— 6§— 6

5£— 4f— 4J— 34— 3— 2f— 2£— 2| — 2f

2§— 3J— 2|— 2J— 3— 3— 2— 2£— 2J-

-104-

-6J-62-
-6-6g

-101-

]— 6-
-6£— 6-

-2^-2f-2i-25_2^-2^_2^-3-f-
a 1 i l __a 1 3 ■; a

8 4 4 28 4 9

This pile according to Colonel Mason's
formula, should have borne 52,556
pounds. I loaded it with 59,618 pounds
and it did not settle. I afterwards in-
creased the load to 62,500 pounds, when
it settled slowly. The greatest weight to
be carried by any one pile was between
30,000 and 35,000 pounds.

The tops of the piles were sawed off
on a level, and the whole surface be-
tween them covered with a flooring of
three-inch planks tightly fitted in, the
upper surface of this floor being flush
with the tops of the piles. They were
then capped in one direction by string-
ers 18"xl8" and 85' long. Each of
these stringers wTas constructed by

splicing two shorter ones of equal
length by means of the regular scarf
joint. These were bound together by
12"xl2" stringers 85' long (formed by
splicing two shorter ones) running over
the line of piles in the perpendicular
direction. These 12"xl2" stringers
were let into the 18"xl8" so that their
top surfaces were flush. In the little
squares thus formed, and next to the
18"xl8" timbers, were laid short pieces
12"'xl2" timbers, and the intervals
filled in up to the level of the latter
with concrete. The whole grillage was
then leveled off with short pieces of 6"
Xl2" planks. This grillage was, there-
fore 18 inches thick. Long sheet piling
was driven for the scarp of the wet
ditch, the upper ends resting on the
inside of the stringers on the outer
row of piles.

In order to distribute the weight of
the tower uniformly over this founda-
tion, strongly reversed groined arches
were turned, the space between their
backs and the grillage being filled in
with solid concrete masonry.

When the brick work of this tower,
which was carried up even on all sides,
was about half completed and the foun-
dation had on it less than half the load
it was designed to carry, the appropria-
tion became exhausted and the work was
stopped. This was in the spring of 1858.
When I visited the work about six months
thereafter I found a marked settlement.
The four salients apparently remained
intact, but on every side the settlement
wras about the same, and largest about
the middle, so that the courses of brick
which were laid perfectly level had the
form of a regular curve.

I was serving at that time as assistant
to Brevet Major G. T. Beauregard, Cap-
tain of Engineers. In addition to his
military works, he was in charge of the
construction of the new Custom House
in New Orleans, La.

In order to ascertain the cause of this
settlement he directed some experiments
to be made by the architect of that build-
ing, Mr. Roy.

I do not remember the details of these
experiments. I was on duty at Forts St.
Philip and Jackson, and afterwards sta-
tioned at West Point while they were
made. The civil war also intervened.
Subsequently, however, to the latter, I

VAN nostranjd's engineering magazine.

met Mr. Boy, and be told me briefly tLat
the experiments proved that piles of dif-
ferent cross sections driven in the same
Louisiana soil and under exactly the
same conditions, do not have a power of
resistance proportional to the area of
their cross section, and that the capacity
of resistance per square inch in cross-
section of pile diminishes as the area of
this cross-section becomes greater. That
is to say, a pile 4" square in cross sec-
tion does not have four times the resist-
ance to pressure of one 2" square. This
decrease, he said, became quite marked
as the cross section of the piles increased.
He believed that the piling for the
foundation at Proctorsville was driven so
closely that the whole system assumed
the character of a single pile about 81
feet square in cross section, and that
therefore its capacity of resistance per
square foot was very much reduced as
compared with the capacity of resistance
per square foot of my experimental pile.
I have never since had an opportunity
to test the accuracy of this conclusion,
but I believe that some of the officers of
our corps are so situated that they can
do it, hence this communication.

From a second letter from Major Weit-
zel to Brigadier- General Wright :

The table of experiments sent by Mr.
Eoy with his letter, and the result of the
experience gained at Proctorsville, La.,
show conclusively, it seems to me, that
although Mason's rule may hold good
for an isolated pile, it cannot be de-
pended upon for a system of piles, such
as are driven for foundations. In order,
therefore, to determine the factor of
safety for such foundations, the views
and experiences of the officers of corps, it
seems to me, would be valuable, and then
if a proper system of experiments could
be made by such of the officers as have
facilities for doing so, it might lead to
practical results in solving this very im-
portant question.

On September 21, 1881, Major George
H. Elliot wrote me a private letter on
this subject. He can undoubtedly fur-
nish you a copy of it. It is very inter-
esting, and the conclusions which he ar-
rives at, seem to me very practical.

I also asked a brief opinion of Lieu-
tenant Colonel C. B. Comstock on the
general subject of pile driving, without-
mentioning to him the special case which
produced my original letter. He has au-
thorized me to use his reply. It is as
follows :

" The energy with which a ram strikes
the head of a pile is spent in changing
the form of the pile, of the ram, in heat-
ing them and making them vibrate, and
in most cases mainly in overcoming the
friction of the earth against the pile, and
in moving the particles of the earth
among themselves, thus causing further
friction.

" The formulae only consider the re-
sistance during the very short period of
the blow. It would be strange if such
resistance were always, for all soils, the
same as when, sometime after the pile
had been driven, it was loaded until it
began to move. Possibly the latter re-
sistance is sometimes the greater, usually
it is doubtless much less, for most ma-
terials require a less force to change
their form slowly than rapidly. A sub-
stance like clay, that is plastic, might re-
sist driving piles very strongly and yet
furnish a very much smaller resistance
to a permanent load. Not knowing the
relation of the two resistances, a formula
which does not include that relation
(i. e., the character of the soil), may be,
even for isolated piles, much in error.
The only way to get a reliable
formula seems to be to determine
for characteristic, well defined, and care-
fully described soils, the ratio between
the resistances given by some good
formula like Bankine's, and the actual
load, which will start the pile very slowly
down and keep it going.

" In soft material a certain load spread
over the surface will carry the whole of
it down bodily to considerable depths.
As soon as a sufficient number of piles in
this area are driven and loaded, they will
do the same, and additional piles are use-
less. In such a case the economical in-
tervals for piles could only be found by
experience."

I submit herewith Mr. Boy's table of
experiments :

PILE FOUNDATION- AND PILB-DRIVING FOBMCLJB.

kr>

A Tabu oi I izi i eumints ox the CoupnEssiBrLrrx 01 Soil of Niw Obu
La., made by Mr. Johx Roy, ix tjie Years 1851 axd 185*2.

8-rf

boa

■Oh

,£3 —

a •""

■_ s

•—• ~j

ZZ ■*—

v a >

do
a
%

Si/t' of bearing, in
square incli

Weight

in pounds,
applied.

o*4

* S
re 2*

*M -

C S3
£> O

«*-. a •

w (h «j

.a w*a

i*" —

P © o ^

—

102.000

o «

3 S £ .S

X* H= tV

6.87fi

1760

Qx l,=- M

85.500

102.0.(0

17(50

tf= A

57.375

102.000

1760

1x1 = 1

102.000

1760

•-»

1x1 = 1

102.0 0

102.000

1760

1 x 2%= %%

2D8.250

102.000

26^

1760

4 x 4 =16

1032. 000

102.00)

1760

1 xlO =16

1632.00.)

102.000

1760

4 x 4 = 10

1632.000

102.000

120

161

1760

/-± ^ -4 — T«

1.125

18.0.10

1760

H* 1 = %

4.500

18.000

3 ■

1760

&x i = Q

0.000

18.000

1760

:4xl = *i

13.500

18.0 '0

1760

1x1 = 1

18.030

18.000

1760

1x1 = 1

36.000

30.000

1760

%x 1 = %

27.000

36.000

i-X

1760

%x i = y2

18.000

36.000

17J0

x 8 = 40

642.000

16.050

1760

1x1 = 4

170.000

42.500

1760

6 xl2 =144

2552.000

17.720

107

400

6 xl2 =144

3362.400

23.350

TS"

182

400

6 x24 =288

15530.00)

54.097

300

20^x20^ = 433

18703.000

43.300

400

12 xl2 =144

5132.00)

35.640

400

24 x24 =570

23150.000

40.200

<$M

300

Weight increased.

45724.000

70.380

300

Weight increased.

57600.000

100 000

18^

300

1x1 = 1

102.000

333

Weight increased.

202.000

121

333

4 x 4 = 16

1632.000

102.000

1&H

333

Weight increased.

3232.000

202.000

54^

121

333

1x1 = 1

103.000

102.000

300

Weight increased.

202 . 000

202.000

300

4 x 4 =16

1632.000

102.000

300

Weight increased.

3232.030

2.2.000

61K

300

Notes — Nos. 23 and 34 were made at the new Custom House, by a Commission of 17. S. Engineers, appointed
by the Treasury Department.

It will be seen, by the above table, that, contrary to the general opinion, a larger surface sinks more than
in proportion to its area.

A very interesting article on this sub-
ject appears in the number of Vax Nos-
traxd's Exgixeerixg Magazixe for October,
1881. It is entitled " Note on the Friction
of Timber Piles in Clay," by Arthur
Cam,eron Hertzig, Assoc. M. Inst. C.E.

Major George H. Elliot to General
Weitzel : Your letter of the 4th of Au-
gust to the Chief of Engineers, relating
your experience in the foundation of the
Martello tower at Proctorsville, La., has
suggested a comparison of the pile driv-
ing formulae accessible to me.

Assuming in these formulae, the case
of the test pile at Proctorsville, -which
was thirty (30) feet long, twelve (12)
by twelve and one-half (12 £) inches at
: top, eleven (11) by eleven and one-half
(11 J) inches at botton ; which weighed
sixteen hundred and eleven (1611)
pounds, and was driven by a ram weigh-
ing nine hundred and ten (910) pounds,
falling five (5) feet at the last blow ; the
last blow driving the pile three eighths
(§) of an inch, the discrepancies be-
tween the results are remarkable. The
extreme supporting power of this pile,

van itostkakd's engikeerestg magazine.

obtained from some of these formulae, is
as follows :

Pounds.
Trautwine . . . . 58,802
Rankiue* 128,50J

Pounds.

Ny strom 17,971

Mason 52,556

Weisbacb 52,556

Major Sander's formula does not give
the extreme supporting power of the pile,
but the safe load only — in this case, 18,-
200 pounds. McAlpine's formula in this
case gives a negative result, as it always
does when W + 228a/F is less than 1, W
representing the weight of the ram in
tons, and F its fall in feet.

Assuming another case, a case in
which the weight and fall of the ram are
much greater, the discrepancies are still
more remarkable. Say that the pile is
of the same size and weight as the one at
Proctorsville ; that it makes the same
penetration at the last blow, and is
driven by a two thousand (2000) pound
ram, falling twenty five (25) feet. The
extreme supporting power and safe load
in this case, according to the various au-
thorities, are stated in the following
table, in which, you will observe, the
relative positions of khe names of these
authorities are not the same as in the
preceding table.

Names of authors of
formula; and rules.

Mo.Upinel1)

Trautwine (2)

Hodgkinson (3)

Nysirom (4)

Rankine(5)

Do. H

Ma-on (8)

WcUhach (9)

Tne Dutch Engineers (10)

S.eve-llyt11)

Sander.- (ls,i

H.-iswelH18)

Rondelet(14)

Perronct (IB)

Rmkine (16)

Mahan(17)

Wheeelur(18)

Rmkiue(19)

Miban C"0)

Wheeler (al)

185,009

219,117

403,450

490,824

810.000(6)

851.200

886.080

J-86.080

886.080

886,<»8J

61,6S9

73,079

40,345

81,804

81,000

130,954

221, 20

48,739

110,760

200,000

2 0,000

69,375

125,802

150,003

150,000

30,0,i0

3 i.COO

30,000

* Assuming the modulus of elasticity to be
750 tons.

(l) McAlpine's formula is P=80(W + .228

VlT— 1), in which P represents the extreme

These discrepancies show that some of
these formulae, or, at least, some of their
factors of safety* are misleading, and it
seems to me that all of them which have
not been based upon experiments on the
capacity of soils to sustain pressures,
must be so.

Let us see what supports a loaded pile.

supporting power of the pile in tons, W the
weight of the ram in tons, and F its fall in feet.
(Journal of the Franklin Instiiute, 3d series,
Vol. LV.). His co-efficient of safety is £.

(8)Trautwine'sformulaisP=- VFxWx.023>

p+1
in which P and F are the same as in Mc-
Alpine's formula; W the weight of the ram
in pounds, and p, the penetration at the la-t
blow, in inches. His co-efficients of safety are
from ^ to -|, "according to circumstances."
In this case and in similar ca^es, I have as-
sumed the arithmetical mean. In ibis case, ^.

(8) This case supposes that the pile is driven
to 1he bed rock through soft mud, and is not
suppporled at the sides. I have assumed in
Hodgkinson's rule (Mahan's Civil Engineering,
p. 80), TV as a co-efficient of safety.

W3F

P— —7^ -., m

(4) Nystrom's formula is
which P represents the

P(Wxm)2'
extreme supporlmg
power of the pile in pounds; W the weight of
the ram, and w the weight of the pile— both in
pounds; F the fall of the ram, and p the pene-
tration jit the last blow. His co-efficient of
safety is ^.

(5) Rankine has a rule that " the factor of
safety against direct crushing of the timber
should not he les* than 10."

(6) Resistance of the pile to crushing.

(7) Assuming in hU formula the modulus of
elasticity to be 750 tons. His formula is

2esp

4WF6S 4tf3s8p3

+ •

in which P repre-

l ' I* I

sents the extreme supporting power of the pile
in tons; W the weight of the ram, and e the
modulus of elasticity, both in tons; F the fall
of the ram, I the length of the pile, and p the
penetration at the last blow, all in feet, and *
the average section of the pile in square inches.
His factors of safety lor use with his formula
ate "from 3 to 10."

W2 F

(8) Colonel Mason's formula is P— . ^n — x~»

W-4-«0 p

in which P represents the extreme supporting
power of the pile; W the weight of the lam; w
the weight of the pile; F the i»\\ of the ram;
and p ths penetration at the last blow. His
factor of safety at Foit Montgomery was 4.

(9) Weisbach's formula is the same as Ma-
son's. His co-efficients "for duration with se-
curity" are from Tlv to TV, the arithmetical
mean if which is T*\s-

(10) Quoted in Proceedings of the Institution
of Civil Engineers (British), Vol. LXIV. Their
formula is the same as Mason's. Their factors
of s.ifety are from 6 to 10. I have assumed the
arithmetical mean of these to find the mean co-
efficient of safety.

PILE FOUNDATIONS AND PILE-DRIVING FORMULAE.

I conceive that there is below the bot-
tom of the pile in ordinary soils a colloi-
dal mass of earth, a, b, c, </, (Fig. 1,)
the particles of which are acted upon by
pressures derived from the weight of the
pile and its loud, and the form and di-
mensions of which depend on this weight ;

It may be n question in ■ Lii^ case, whether the !

mean co-cflicii nt of saf< ly should be t*1^. t\t °r i
}. T '. 4 is the gcometn'ca1 mean of \ and ^a, which
are the co-efficients of safety corresponding to
the « xtnme factors of safcy, aod il \v:is usi-d
hy the Engineer of the Porismoulh (Eniihtnd) :
Docks, as I nuan co-emYient, to fiod the safe \
value of P f'>r the piles of his work, fiom the i
formula and factors of safety of the Dutch En-
gineers. A similar doubt arises in finlimr a
meau co-efficient of safety from Rankine's fac-
tors <>t safety.

(,x) Quoted in Thomas Stevenson's "Deshrn
and Construction of Harbours." His formula
is the same as Mason's. No factor of safety is
givi n.

(18) Tne extreme supporting power of a pile
is not «iiven in the formula of Major Sanders,
which he contributed to the Journal of tne
Franklin Institute, and which may be found
in Vol. XXII., (3rd Series). The formula is

WF
P= q— , in which P represents the safe load of

the pile; F the fall nt the ram; andp the pene-
tratiou at the la*t blow.

(lsj Major Sanders' formula adopted by Has-
well.

I14) 427 to 498 pounds to the square inch of
head of pile. Quoted in Professor Vose's" Man- !
ual for Railroad Engineers."

(15) From his rule found in (Envres de Per-
ronet. ■ ■ Nous estimons pour ces rations, quel 'on
ne doit point charger ks pilots de S a 9 pouces de
grosseur, de plus de cinquante milliers; ceux c'un

de plus de cent milliers; et ainsi des avtres a
proportion du quarre de leur diametre ou de la
superficie de leur tete."

1 millier=K-79.22 pounds. 1 pied=12.8"

(16) 1000 pounds to the square inch of head
of pile.

(17) The same.

(18) The same.

(19) "Piles standing in soft ground by fric-
tion."

l*°) "Piles wlrcb. resist only in virtue of the
friction arising from the compres-ion of the
soil."

(-1) "When they resist wholly by friction on
the side*."

* By the term "factor of safety," whh-h is
used by many of the authorities on founda-
tions, is meant the number which is to be mul-
tiplied into the working had, in any case, to
find the "extreme supporting power" of the
pile, or the resistance of the soil, to which, for
Safety in that ca^e, the pile is to be driven.

The ierm "oo-etti< ient " of safity is used by
McAlpine. It is a fraction which is to be mul-
tiplied into the "ex.reme supporting power" of
the pile to tind its safe load. It is the recipro-
cal of the corresponding " factor of safety.

and on the kind of soil ;| that at every
section ey f ; c, /', of the pile below the
surface of the ground, the particles of
earth in contact with the pile, are, by
reason of friction, pressed downward,
and that these pressures are distributed
(spread) in the same way that the press-
ure at the foot of the pile is distributed ;
that is, through the particles of the
earth surrounding the pile, which are
limited by conoidal surfaces, of which,
(in homogeneous soils), the pile is a
common axis.J

Are the particles of earth, within these
conoids of pressure and distant from the
pile, acted upon by the blows of the
ram?

General Tower, in remarking upon a
recent device by a citizen of Virginia,for
an armor protection of fortifications,
consisting of a thin iron or steel plate
backed by springs, said that even if the
plate were one foot thick, suspended by
chains, anc^ without any backing what-
ever, it would be penetrated by a shot
from an 81- ton gun in about -r^Vo" of a
second, and before the plate could move
perceptibly.

Is it not probable, reasoning from
analogy, that the blows of the ram upon
the head of a pile reach only the par-
ticles of earth which are in contact with
or very near the foot and the sides of the
pile ; that the action (occupying only a
small fraction of a second) is too quick
to be communicated to more distant par-
ticles composing the conoids of pressure,
and that subsequently the forces which
hold these particles in place may be dis-
turbed, and the particles may yield, un-
der continued pressures communicated
successively through the pile, and the
particles of earth in contact with and
near the pile ?

It might appear at first sight, that if
pressures are more disturbed laterally
in the earth below and around a pile, the
resistance to pressures must be greater
than the resistance to blows, but the

t None of the books available for reference throw
any lijrht on this subject. Kai.kine has a theory con-
cerning the pressures within an earthen mass derived
from its own weight, but he gives no result" of experi-
ments if any have been made , touching the action of
earth un<l»;r exterior pressures.

X In sticky soils, no doubt, the action of the parti-
cles oi eartu adjoining a piie, is, in part, oue of draw-
ing or puhint; downward the particles of earth ex-
terior to them, and the distance to which this action
extends, depends on the degree of adhesion of these
particles.

VAT* NOSTRAND'S ENGINEERING MAGAZINE.

truth is, that it cannot be said that one is
greater or less than the other, except by
empirical comparisons between the ef-
fects of blows and the results of press-
ures.

When these comparisons in the case
of any kind of soil have been made, the
true relation between these effects and
these results may be discovered, and cor-
rect and reliable factors of safety for use
with formulae for the sustaining power of
piles, into which formulae enter the terms
common to all pile-driving formulae,
(viz., the weight of the ram, its fall and
the average penetration of the last
blows), may be made for that kind of
soil, but I think it evident that no pile-
driving formula or factors of safety based
only on theoretical deductions from the

formula Ps=-^-, can be relied od, even

for single isolated piles, or for piles
driven at considerable distances apart.

Now, let us examine the case of an or-
dinary pile foundation in any compress-
ible soil. Say that the piles are driven
three (3) feet apart, in rows the same
distance apart, from center to center.

Would a safe load for this foundation
be equal to the safe load of a single iso-
lated pile in that soil, multiplied by the
number of piles ?

I think not, for, if it be true that be-
low and surrounding the piles, there
exists within the soil the conoids of press-
ure before alluded to, and if the sur-
faces of these conoids make any consid-
erable angle with the vertical, then the
pressure upon the earth below and be-
tween the piles, may be much greater in
the case supposed, than in the case of an
isolated pile.

Let Fig. 2 represent a plan of the piles
of this foundation, and let Fig. 3 repre-
sect a section through one of the rows.
Let a, 6, c, (/, Fig. 3, represent a sec-
tion through the axis of the conoid of
pressure arising from the pressure of the
pile and its load, at the foot of the pile
A, and let a ', b\ c\ d\ represent a simi-
lar section through the conoid of press-
ure at the foot of the pile B. Let us
pass a horizontal plane at any short
distance — say eighteen (18) inches — be-
low the feet of the piles (which we sup-
pose to be driven to a uniform depth),
and let i, i, i, i, and k, k, k% Jc, Fig. 2,

represent in plan, and let mt n, and m!
n, represent in section, the areas cut
from the conoids of pressure by this
plane, and it will be seen that consider-
able portions of each of these areas, ma}'
be acted upon by pressures derived from
both of the piles and their loads. The
same may be said of the earth within the
conoids of pressure surrounding the
piles, and it appears, therefore, that the
forces acting upon the particles of earth
below and surrounding a pile, may be in
equilibrium, and the particles may be at
rest, in the case of a loaded isola£ed pile,
when the equilibrium may be disturbed,
and the particles may sink with the pile,
when the same load per pile is laid upon
a foundation composed of piles driven in
the same soil at such distances apart that
their conoids of pressure intersect each
other.

McAlpine, before constructing the
Brooklyn Dry Dock, made experiments
with loads upon piles,* and of his formula
he says :

" The co-efficient is reliable for such
material as was found at that place."

This material was " a silicious sand
mixed with comminuted particles of
mica and a little vegetable loam, and was
generally encountered in the form of
quicksand."

McAlpine also says :

"It is very desirable that similar ex-
periments should be made in soils of dif-
ferent kinds, which would make this for-
mula applicable to all the cases usually
met with in constructions."

Major Sanders experimented by load-
ing sets of piles of four each, and Colonel
Mason made his formula when the fort
(Montgomery) which he was construct-
ing on a pile foundation, had been nearly
completed.

Which of the other pile-driving for-
mulae and factors of safety given by the
authorities I have quoted, were deduced
from experiments in loading more than
single isolated piles, I do not know, but
some of the formulas appear to have been
based only on theoretical considerations,
and some of the factors of safety appear
to be simply conjectural.

None of the formulae are accompanied

* As far as I can determine from his paper read be-
fore the Franklin Institute, January 15, 18G8, these
experiments were made (by means of a lever;, upon
isolated piles only.

PILE FOUNDATIONS AND PTLK-nniVIXO FOKMULJE.

VAN NOSTRAND'S ENGINEEEIKG MAGAZINE.

by tables of factors of safety, correspond-
ing to specified kinds of soil.

It is factors of safety that are most
needed. There are many formulae.
Doubtless most of them are good, and

W F

one of them— P=^ X-,— has been

deduced independently by several dis
tinguished authors ; but can any of them
be used safely and confidently, when the
factors of safety furnished by the authors
of these formulae produce results so dis-
cordant?

An engineer having to construct a pile
foundation, must take some pile-driving
formula and factor of safety, as he finds
them. He has no time to make proper
experiments in the soil he has to deal
with, for that would require years of
time.

It is not enough for his purpose that
an author of a formula prescribes for use
with it, a single factor of safety of 3, for
example, for he knows that that factor
can only be a proper one for one kind of
soil, and he is not told what the kind
of soil is. It may be more, or it may
be less easily penetrated than his own.
In the former case, by the use of an un-
necessarily large factor of safety, he
would make his foundation unnecessarily
expensive ; and in the latter, his founda-
tion would be in danger of yielding,
sometime, under its load. Neither is he
satisfied to be told to use a factor of
safety from 3 to 10 ; from 6 to 10, or
from 10 to 100, "according to circum-
stances." He wants his own case and
its proper factor of safety to be, as
far as possible, definitely stated, or else,
it seems to me, he would prefer to drive
the piles of his foundation in every case
of importance, as far as they will go, or
to the equivalent of their " absolute stop-
age,"* which, he knows, would make
his foundation as safe as a pile founda-
tion can be made, though it may be ex-
pensive.

I think that the want of reliable and
definite factors of safety can, in a man-
ner, be supplied, without waiting for ex-
periments made for the purpose.

*p=. 0067" when W=830 pounds and F=5'. See Ma-
han's Civil Engineering. It is the retus dv mouton de-
scribed in (Eiores ds Perroaet. By Mason's formula,
It appaar.5 th.it this equivalent would be reached when
sevenr7i blows from a two thousand 2,000) pound
ram, falling twenty-five 25; feet, would sink a sixteen
hundred and eleven (1611; pound pile one (1; inch.

While it is difficult, no doubt, to make
minute descriptions of soils by giving
the proportions of their physical constit-
uents, I think that a table of useful fac-
tors of safety, corresponding to quite a
large number of the ordinary and easily
recognizable soils, could be made for
use with any good formula, say Mason's,
from the past recorded experiences of
the officers of the Corps of Engineers.
This could be done by dividing the
values of P deduced from that formula,
(substituting in each case for W, F,
tr, and p, the actual weight and fall of
the ram, the average weight of the piles,
and the average penetration at the last
blows) by the actual weights of the struc-
tures per pile.

A comparison of all the factors of safe-
ty, obtained in this way, which would
arise from cases in which foundations in
any specified kind of soil have carried
their loads for some years without any
evidence of settling, would probably
show that no two of them would be pre-
cisely the same, and that some of them
would be excessive. These latter, which
would lead to unnecessarily expensive
work, and any inadequate factor which
might be developed by a failure of a
foundation, like the one at Proctorsville,
to carry its load, could be rejected. A
fair judgment could then be taken in
respect of the others, and a single safe
and reliable factor for that kind of soil,
could be determined on.

From the foregoing considerations, I
come to the following conclusions :

1st. Pile-driving formulae should be
accompanied by tables of factors of safe-
ty, corresponding to all the common
and easily recognizible kinds of soil.

2nd. These factors of safety should be
determined on after extended experi-
ments on the supporting power of piles,*
although approximate factors' which
could be used withoub hazard, could be
found from examinations of the records
of the driving of the piles of actual
foundations, provided the weights of the
superstructures are known, and descrip-
tions of the soils have been preserved ;
and provided, also, that the foundations
have carried their loads during sufficient
lengths of time.

* The case mentioned by you shows that the testing
by loading should extend over considerable lenuths
or time. Even the foundations of Fort Montgomery
and Fort Delaware have settled more or less.

NEW FORMULA FOR TTTF TORSION OF PRISMATIC BODIES.

3rd. In experiments on the support'
ing power of piles the loads should not
rest upon single isolated piles, but they
should cover ;i number of piles, driven at
those di stances apart which are usual in
pile foundations.

4th. In every case of construction of

a pile foundation, the record of the driv-
ing of the piles, should include suih a
description of the soil, obtained for bor-
ings, as would enable an engineer, hav-
ing to found a work in a similar soil, to
recognise it.

EXPERIMENTAL PROOFS OF SOME NEW FORMULA FOR
THE TORSION OF PRISMATIC BODIES.

By PROF. J. BAUSHINGER.
From "Der Civilin^enieur," for Abstracts of the Institution of Civil Engineers.

The author commences with nearly a
column of explanation of the symbols
used, and then applying his formulae to
five bars of the following sections : (1)
circular ; (2) elliptical, with axes in ratio
of 1 : 2; (3)square; (4) rectangular, with
sides in ratio of 1:2; (5) rectangular,
with sides as 1 : 4, he deduces the follow-
ing equation : —

dt : d% : d,

d4 : d =
1: 1.25 : 1.13: 1.40:9.1,

where c?, is the amount of rotation which
a cross section of the circular bar takes
relatively to a parallel one at a fixed dis-
tance from it under the action of a given
force ; d9 is the corresponding amount in
the bar of elliptic section under the same
force, and so on.

It should be noticed that the dimen-
sions of the bars are so adjusted that the
areas of Njs. 1, 2. 3 and 4 are equal to
each other, and the area of No. 5 (sides
as 1 : 4) half either of the others.

By an approximate formula the above
quotation becomes =

d1 : d, : d, : di : d =

1:1.25:105:1.31: 8.9.

Experimental results were obtained as
follows : — Five pairs of bars of cast iron
each 100 centimeters long and of the
above sections were twisted in a Wer-
ders testing machine as explained in the
author's already published JZisais de
lleslstame. The cross sections, the rel-
ative rotations of which were measured,
were 50 centimeters apart, and the rota-
tion was measured on the arc of a circle
of 350 centimeters radius (or rather on

the tangent to such a circle) by means of
telescopes, special precautions being
taken to eliminate errors and secure
exact readings. Tables of results are
given, from which it appears that taking
the circular bar as the standard of com-
parison, experiment agrees well with
1 he Dry in the case of the bar of elliptic
section ; but the agreement is not so
close as could be desired with the square
and rectangular bars. With them the
observed rotations are greater than the
values given by the first of the above
equations, and harmonize still less with
those of the approximate equation, which
are smaller than those obtained from the
rigorous formula.

Reference is made in the paper to ex-
periments on torsion, the particulars of
which are given in tables 122 to 147 of
the Essais de Resistance already referred
to. These experiments were made on
bars of Siemens Martin steel of various
degrees of hardness, of Bessemer steel
similarly varying, and of iron both granu-
lar and fibrous in texture. The bars
w«re 660 millimeters long, and circular
or square in section, the diameter or side
being in each case 10 centimeters. By
the formula the relative amount of rota-
tion of two bars of the same material
should be given by

tf, : dt :: 1 : 0.698,

and though there is some discrepancy
between the experimental and theoretical
results in individual cases, yet the aver-
age of thirteen pairs of bars gives

d9 :: 1 : 0.696.

VAN nostkand's engineering magazine.

The thirteen values range between
1 : 0.633 in iron bars of fine grain,
and

1 : 0.747 in Bessemer steel bars.

A further proof of the formulae is ob-
tained by deducing from them the mod-
ulus of shearing elasticity (?;), and com-
paring the results with those obtained
from the formula,

V 211 + A*)'

where e is the modulus of tensile or com-
pressive elasticity, and jj. is the ratio be-
tween the sectional contraction or dilata-
tion, and the increase or diminution of
length produced by direct tensile or com-
pressive stresses. Tables of values are
given, and they agree as well as could be
expected when the minute quantities to
be measured are considered, and it is
worthy of notice that the ratio jx is prac-
tically independent of the form of the
cross section.

A formula given by^ the author for the
maximum sheering stress produced in a
section by torsion, cannot be proved di-
rectly, since it is impossible to measure
the stress at any precise spot. The
method adopted was to increase the mo-
ment of torsion till rupture ensued, and
to compare the correspondiDg values of
maximum stress as given by the formula
(which may be callei the "strength of
torsion") {torsions f est igkeit), in the case
of bars of different sections. As might
be expected, the form of the cross sec-
tion had in this case very great influence
on the result; the section of greatest
strength being the circular, and next to
it the square, the least favorable being
the rectangular with sides as 1:4. The
proportional figures for the maximum
stress produced by an equal moment of
torsion were

1:1.414:1.269:1.795:2.539,

the order of the bars being that previ-
ously given.

Tne author proposes to make further
experiments on the torsion of bars of
similar sections but of varying dimen-
sions.

Application of the Radiophone to
Telegeaphy. — By E. Mecadier. — The au-
thor causes each radiophonic transmitter
to induce vibrations in the electric circuit
corresponding to a definite musical tone,
and by intermitting the rays of light
falling on the perforated revolving disc,
by a disc attached to a Morse key, ob-
tains in each receiving telephone Morse
signals in musical tones. By instructing
each operator to distinguish only those
signals corresponding to a given tone, it
is found possible to transmit numerous
messages in either direction at one and
the same time. The selenium cells of
the radiophones and the telephones are
all included in a single direct circuit. —
Comptes rendus cle VAcademie des
/Sciences.

Electrical Thermometers for Observ-
ing Temperature at a Distance. — By Max
Lindner. — In 1877 Herr Eichhorn made
experiments with several platinum wires
hermetically sealed into the sides of a
thermometer, at such distances that a
rough graduation was possible by the
electrical contact made by the rising or
falling mercury ; and in this year he used
the instrument in a malt manufactory,
with much success, for the regulation of
the heating arrangements.

For use in brewing, the firm of Oscar
Schoppe, of Leipsic, enclose the thermom-
eter in a wooden case, and they can
connect the several wires at will with
electro magnetic bell arrangements, so
that a bell rings as soon as the tempera-
ture reaches a certain height. The dis-
tances to which these wires have to be
taken are usually small, and onfy a few
wires are necessary, so that the cable is
not of an expensive character. The in-
sulating material of the silk- covered wires
of the cable is asphalt. The temperatures
of cooliig vessels, as well as heating ves-
sels, are controlled by means of these
thermometers, which are also employed
for opening and closing ventilators, &c.
They act very well everywhere, and may
be depended on, and this is in favorable
comparison with the bad action of the
ordinary thermo-electric thermometers.
Zeltschrift fur Angewandte Eltktric-
itatslehre.

CANDLE POWKK OF THE ELECTEIC LIGHT.

CANDLE POWER OF THE ELECTRIC LIGHT.

By PAGET Ulcus, LL.D.
From Proceedings of the Institution of Civil Engineers.

Very varying statements are constantly
before the public as to the candle power
of diverse devices affording the elec-
tric light. None of these statements ap-
pear to be compatible, neither does any
law of difference immediately present it-
self. Just as in a diagram of results the
sanguine mathematician may picture to
himself the curve representing a definite
law where the unimaginative observer
can perceive only a chaotic zigzag of dots,
so with a little bias there, and a small
subtraction here, some order may be
evolved from the figures relating to the
electric light. Such an attempt is made
in what follows.

The most salient point for a unit of
comparison is the number of heat units
represented by electrical measurement,
in ratio with the candle power meas-
ured optically. But at the outset a diffi-
culty, or rather an uncertainty, is experi-
enced ; this refers, however, only to arc-
lights, of which there are two systems of
measurement — one system with the car-
bons on the same axis, the other with the
axis of one of the carbons forming a very
acute angle with the axis of the other
carbon, so that the glowing crater of one
carbon forms a reflector to the point of
the other. In the latter case, consider-
ing the light of the former as unity, the
light may be about 1.66 time stronger as
measured. This has been pointed out by
Mr. Douglass, M. Inst. C.E., in a Report
to the Trinity House. Another source
of discrepancy is the want of knowledge
of the specific heat of the vapor of the
electric arc, and of its temperature, both
unknown quantities; if the one were
known, the other could be determined.

Taking the ratio of units of heat repre-
sented per candle power, the subsequent
figures will show a large margin of econ-
omy for arc lighting over incandescent
lighting. This will of course be true
of the arc considered only as a furnace
producing a greater heat in a smaller
space then by incandescence; and it ap-
pears to the author to be true for an-
Vol. XXVH— No. 1—3.

other reason. Whatever may be the spe-
cific heat of the vapor of the electric arc,
it is certain that over the given resistance
of the arc, as compared with an equal re
sistance of the incandescent lamp, the
mass of the arc, measured by the mole-
cules it contains, is far less than that of
the solid carbon; and the amount of work
to be done by the current from this cause
will be so considerably less, as to lead to a
prophetic renunciation of greater econo-
my of expended energy than is really
found.

To return to figures. Suppose a light
of 1000 candle power, measured with the
carbons on the same axis, be produced
with 4.5 ohms resistance and 10 webers
of current, there will be represented 108
gramme degrees of heat, or nearly 0.1
gramme degree per candle power per sec-
ond. This is deducible from the figures
given by the Brush system. It does not
include the heat due to consumption of
carbon in air, which is inconsiderable.

In a Siemens lamp tested by the au-
thor, about 3,000 candle power, of dif-
fused beam, was obtained with 36 webers
current, when the lamp had 1 ohm of re-
sistance in the arc; this corresponds to

(OOPT \
q"7wT/ 0*112 un^ Per

candle power. In a Serrin lamp, fed
from a Gramme machine, the author ob-
tained a light of 3,600 candle power with
45.7 webers current, the arc having 1£
ohm resistance, corresponding to 624
heat units, or 0.17 unit per candle. A
Crompton lamp, fed by a Burgin machine
gave a light said to be of 4,000 candle
power; but assuming this to be from bi-
axial position of the carbons, about 2,000
candle power would correspond to 180
heat units for 16 webers on 2.93 ohms,
or about 0.09 heat unit per candle power.
On (about) the same resistance of arc in
a Crompton lamp, 24 webers yielded the
author 3,600 candle power, or about 403
heat units, corresponding to 0.12 heat
unit per candle power.

Numerous measurements are recorded,

van nostkand's engineeking magazine.

all varying greatly, partly and chiefly be-
cause of the variations in the measure-
ments of candle power. All the measure-
ments, as recorded by the author, have
been made by the same method from the
diffused "beam."

Their mean may therefore be taken for
comparison with subsequent numbers.
It is 0.118 gramme degree per candle
power.

As 1 gramme degree =42 million ergs,
1 candle power represents 4.9 million
ergs. As a foot pound is 13.56 million
ergs, each candle power represents 0.364
foot lb. per second, or 1,511 candle power
per HP., a rough check upon the foregoing
figures.

The late Mr. L. Schwendler, M. Inst. C
E., has stated in a Paper (fragmentary
to the author) that the standard candle
does work at the rate of 610 meg-ergs in
a second, whilst the unit of light is pro-
duced electrically at the rate of not more
than 20 meg-ergs in a second. This lat-
ter figure is very high if it refer to arc
lighting, for, although at the trials under
the auspices of the Franklin Institute,
when only 380 candle power per HP.
were obtained, there were estimated to
to be (6.5x0.252=) 1.6 gramme degree =
67 meg-ergs per candle power, great
strides have since been made. Mr.
Schwendler's figuies are now at along
discount, and would appear correspond-
ing to a still lower state of the art if the
figures given by others be correct as to
candle power of the lights. As has been
stated, however, the figures given in this
Paper are intended to be only intercom-
para tive.

Another type of lamp is the Werder-
mann, which may be termed an arc incan-
descent lamp, because the light is obtained
from the incandescence of a cone of car-
bon resting at its apex on a negative elec-
trode of larger section, and from the arc
that plays between the sides of the carbon
cone and face of the negative electrode.
Ten of these lamps, giving 40 candle-power
light, each burning 4.5 millimeter carbons,
yielded about 0.88 heat unit per candle
power. A series of these lamps averaged
306 candle power, with 50 webers current,
the resistance of each lamp being 0.1337
ohm. This corresponds to 80 heat
units per lamp, or to 0.262 heat unit
per candle power. Thus, the small light
is a sub-multiple to a considerable degree

of the larger light, want of economy com-
mences to be evident, and an average can
no longer be taken.

A Joel lamp, one of a series of ten, is
said to have afforded 320 candle power,
with an electro-motive force of 130 volts,
sending a current of 50 webers through
the series, corresponding to 156 heat
units per lamp, or 0.49 heat unit per
candle power.

These notes, however crude, have
more weight when purely incandescent
lamps are considered. In this case
measurement becomes easy, for the light
approximates in color to that of the
standard candle employed, and the resist-
ance of the incandescent fiber is suf-
ficiently constant to yield concordant re-
sults.

One of Maxim's earliest lamps was
measured by the author, and found to
indicate 3.6 ohms when cold, and 1.9 ohm
when giving 11.5 candle-power light with
a current of 5.5 webers. This corre-
sponds to 0.83 unit per candle power, or
about 140 candle power per HP. It
should be remarked that with this cur-
rent the loss due to heat per unit of re-
sistance in the conductors would be 3
per cent, as against the 0.1 per cent, for
a weber current. Another Maxim lamp
of about 64 ohms when giving 50 candle
power, and 116 ohms when cold, with 1.3
weber current, would correspond to 0.52
heat unit per candle power. An Edison
lamp, in the author's possession, meas-
ures 61 ohms when cold and 33 ohms
when hot, and indicates, with 1 weber of
current, 11 candle power, equivalent to
0.73 heat unit per candle power.

A Swan lamp had not, at the time of
the author's measurements, found its way
to America ; but there are several state-
ments as to the candle power of this
lamp. It would appear that with 160
volts and 24 webers of current, 24 rows
of two lamps in series, or 48 lamps, each
of 84 ohms resistance, gave 48 candle
power each. Assuming that this was the
resistance of the lamp when cold, that
the resistance when incandescent would
be 33 ohms, and that there would then
be 2 webers passing through each lamp,
this would correspond to 0.66 heat unit
per candle power. These are, however,
assumed figures.

It should be clearly understood in
estimating the work done in any carbon

CANDLE POWER OF THE ELECTRIC LIGHT.

ar)

focus that the resistance of the carbon
decreases with the increase of tem] >
hire, and that, if the current be directly
taken from a dynamo machine, con-
structed on the mutual accumulation
principle, there will be considerably more
current flowing through the lamp than
an estimate based on a potential measure-
ment will allow.

The following table furnishes a com-
prehensive view of the results obtained.
(The figures are only roughly calculated.)

A 5-feet gas-burner supplying K; candle
power light would cost for a 4-light chan-
delier, for 20 cubic feet of gas, in New
York $2.50 X -02 = $0.05 or 5 cents an
hour. At $40 a year cost, or adding 25
per cent, for profit, at $50 a year, 1 HP.
can be had for about 300 working hours

a year ; and ' = 6.16 cents an hour,
oOU

or — — — 4.15 cents per hour for the elec-

Table I.

Actual Dif-

Candle Power

Gramme De-

Foot lbs. per

fused Light

per HP. in

gree per

Candle Power

per Second.

Minute per

Remarks.

in Focus.

Focus.

Candle Power

1,000

1,774

0.10

Arc.

Brush.

3,000

1,650

0.11

• t

Siemens, as found.

3,600

1,030

0.17

Serrin.

3,600

1,500

0.12

< i

Crompton.

....

1,500

0.12

(Mean.)

200

0.88

164

Incandescent.

306

684

0.26

«<

Werdermann.

320

363

0.49

Joel.

214

0.83

154

Incandescent Maxim.

280

0.64

119

a n

345

0.52

(f u

245

0.73

136

Edison.

270

0.66

123

" Swan, estimated.

It is at present impossible to estimate
the loss due to decrease of resistance in
the carbon by expenditure of heat, but it
must be considerable.

The author hopes that from this it will
appear in how far the incandescent light
is theoretically more costly than the arc
light, as about 6 to 1. But in practical
use there are other considerations, not
the smallest of which is the attendance
arc lights require to maintain their store
of carbon.

The light employed in ordinary domes-
tic avocations is approximately 1 candle
(standard) at 1 foot distance. Assuming
an average distance of 8 feet for domestic
lighting, the electric chandelier must be
of 64 candle power to give the same
" surface intensity," in a room 16 feet
square and of slightly more than ordi-
nary height. The incandescent lamp will
give this light at an expenditure of 0.6
heat unit per candle power, or 38.4 heat
units per light center, or say four chan-
deliers per HP.

I trie chandelier. This shows that, even

J now, were a reasonable commercial profit

taken, the electric light, in the United

States at least, could compete with gas.

A paper by Sir William Thomson and
Mr. Bottomley, entitled " The Illuminat-
ing Powers of Incandescent Vacuum
Lamps, with Measured Potentials and
Measured Currents," * read at the last
meeting of the British Association, con-
tains a table from which a valuable law
can be deduced, a law that the author
first enunciated before the Institution in
1878. It is that the light in an electric
system varies as the fourth power of the
current whose resistance or potential is
constant, or as the second power of the
work in circuit. To illustrate this,
columns a, b, c and cl have been taken
from the tables in the paper referred to,
and e and / calculated. The agreement
is sufficiently close.

The value of the candle power in heat
units is higher than observed by the

* Vide" Nature," vol. xsiv., p. 490.

VAN nostkand's engineering magazine.

author, and this is probably due to the
method employed in measurement of the
light, which is more wasteful of the ob-
served rays than that used by the author.
The law just referred to is illustrated
by the following table :

1 able II.

'■d «m

« o •

5 O ^3

§^

"3 S3 J5

0.093

56.9

1.21

11.6

1.00

1.0

65.5

1.46

0.129

25.0

2.16

1.9

70.2

1.64

0.156

42.0

3.62

2.8

74.1

1.81

0.181

44.0

3.79

3.9

76.1

1.82

0.187

55.0

4.75

4.1

78.0

1.99

0.210.

63.0

5.42

5.2

80.3

2.06

0.224

66.0

5.70

5.9

81.9

2.06

0.228

76.0

6.54

6.2

84.6

2.06

0.235

82.0

7.05

6.5

87.0

2.10

0.247

84.0

7.24

7.2

90.9

2.17

0.267

102.0

8.80

8.4

99.1

2.21

0.296

114.0

9.85

9.8

Considering that in the measuring gal-
vanomoter, although^ very accurate in-
strument, the deflections are merely pro-
portional to the effect, and liability of
error will be small ; and that in the pho-
tometer used (an inaccurate instrument)
the measurements vary with the second
power of the distance, whilst the light
under measurement varies with the fourth
power of the current, the departures from
agreement of the observed and estimated
figures may be fully ascribed to errors of
observation.

DISCUSSION.

Mr. J. W. Swan remarked, through the
Secretary, that even if the material was
not as large, nor the conditions, under
which the observations were made, as
perfect as could have been wished, the
paper at least formed an interesting con-
tribution on a difficult and important sub-
ject. He doubted, however, whether the
facts adduced were sufficient to establish,
or even to strongly supportj the theo-
retical views expressed, more particularly
with regard to the comparative economy
of the arc light and of the incandescent
light. He failed to see why it might not
be possible to obtain as large an amount
of light for a given expenditure of energy
invested in a series of incandescent lamps

as in an arc light. It was perhaps not
possible to raise the carbon filament of
an incandescent lamp to quite the same
degree of intense brilliance as the crater
in the positive electrode of an arc lamp ;
but there was full compensation for the
somewhat lower incandescence of the
carbon filament in the large radiating
surface obtained through a multiplication
of such filaments. He had seen pro-
duced by incandescent lamps the light
of between 2,000 and 3,000 candles
by the expenditure of 1 HP. He did not
say that the lamps were durable at the
exceedingly high temperature to which it
was necessary to heat the filaments in
order to obtain this result ; but that was
a practical consideration, and he merely
submitted the fact as bearing upon the
theoretical view sought to be established
by the tables. He noticed a discrepancy
in the figures on which the calculation of
the HP. product of light from Swan lamps
was based. It was stated that there were
24 rows of lamps with two lamps in each
row, that the light given by each lamp
was 48 candle power, that the current
was 24 webers and the potential 160
volts. The resistance of the lamps cold
was mentioned, but the resistance hot
was assumed, and this assumption was
supposed to introduce an element of un-
certainty into the calculation. But if the
current and the electro-motive force were
known, and both these were stated, the
one as 160 volts and the other as 24
webers, that was one weber through each
of the 24 lines, and therefore through
each lamp — a current more likely to be
correct than the 2 webers also men-
tioned, and which presupposed a total
current of 48 webers instead of 24 given
as the total; then it followed that the
light per HP. was 438 candle power, and
not 270, as given in the table of measure-
ments. Probably it had been overlooked
that as two lamps were in series, the 160
volts electro-motive force, and one weber
current, lighted two lamps, and that the
united light of the two must therefore be
taken as the product of this expenditure
of energy. Whether this was the cor-
rect explanation of the error or not, it
was certain that with the correction he
had suggested the result was much more
concordant with the numerous other
measurements. Referring to the remark,
" that from this it will appear in how far

c.YXDLE POWER OF THE ELECTRIC LIGHT.

the incandescent light is theoretically
more costly than the arc light, us about
6 to 1," he would only add, that it ap-
peared to him that a much broader basis
of observation than that supplied by the
tables of measurement contained in the
paper was required to support the theory
Bought to be erected upon it.

3Ir. H. Wilde observed, through
the Secretary, that in considering that
part of the paper which related to incan-
descent lighting, the following observa-
tions might perhaps be found useful. In
the various accounts and descriptions of
this method of lighting which had ap-
peared from time to time, a striking feat-
ure was the absence of any precise infor-
mation as to the amount of disintegration
of the carbon tilament during the trans-
mission of the electric current, and on
which the durability or life of the lamp
depended. The determination of this
question, as would be obvious, preceded
all others in order of importance, when
the new method of lighting was com-
pared with other illuminants in point of
economy and convenience. From ex-
periments which he had made, with
Swan's lamps of the most recent manu-
facture, he had found that the carbon
filament, after being maintained at the
parliamentary standard of a single gas
light of 16 candles, broke down in one
hundred and forty to one hundred and
fifty hours. In these experiments care
was taken to maintain the light as nearly
uniform as possible, and the comparison
was made by Rumford's photometer and
a standard wax candle. After the lamps
had been lighted for some hours, a de-
posit of carbon was formed in the in-
terior of the glass globe, which was at-
tended by a visible diminution of the
thickness of the carbon filament. This
deposit increased in density sufficient to
diminish the available light from the
filament by 3 or 4 candle power before it
broke down. The depth of coloration of
the glass globe afforded a ready means
of estimating, approximately, the number
of hours which a lamp had been in oper-
ation at a given candle power. Further
observations indicated that the durability
of the carbon filaments of incandescent
lamps was inversely proportional to the
square of the luminous intensity. Hence,
the life of a carbon which was one hun-
dred and fifty hours at a power of 16

candles would be extended to six hun-
dred hours at a power of S caudles ; while
with a power of 32 candles the life of a
carbon would be diminished to thirty-
eight hours. It would therefore appear
that this lamp was only practicable for
light below 16 candle power.

There was no reason to expect a better
duty from other incandescent lamps in
which a carbon filament was used than
was obtained from the Swan lamp, as the
metallic lustre and ring of the filament
in this lamp showed that the conversion
of the hydro carbon, of which it was com-
posed, into pure carbon, had been com-
plete. The determination of the dura-
bility of the filament of an incandescent
lamp thus afforded a basis of comparison
with other methods of illumination in
point of economy. Now, 750 cubic feet
of standard, or 16 candle gas, were the
equivalent of the life of a Swan lamp of
the same illuminating power for one
hundred and fifty hours, which, with gas
at 3s. per 1,000 cubic feet, the price in
London, amounted to 2s. 3d. for the same
amount of light for one hundred and
fifty hours as from a Swan lamp. In
this sum was included the cost of manu-
facture, distribution, and profit on the
gas, which was not more than the manu-
facturing cost of renewing the incandes-
cent lamp alone. He left untouched the
subject of the generation, distribution,
and subdivision of the electricity for
lighting incandescent lamps over large
areas, as it was attended with so many
difficulties, electrical and mechanical,
that all comparison with regard to cost
would be purely hypothetical ; but which,
even if these chfficulties were overcome,
would place the cost of incandescent
lighting largely in excess of the cost of
gas light. While viewing, as he did, the
substitution of incandescent for gas light
as a retrograde step in general domestic
and public lighting, there were special
applications of the new illuminant which
were of undoubted value. The lighting
of the interior of steamships by incan-
descent lamps had so far been attended '
with very promising success ; but in this
case considerations of cost were far out-
weighed by the superior advantages of
comfort and convenience which the new
illuminant afforded over oil lights, for
which it was substituted. Other uses
would without doubt be found hereafter

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

for incandescent lighting ; and although
its application might not be so universal
as the promoters of it anticipated, the
invention promised to be a permanent
and valuable addition to the resources of
artificial illumination.

Mr. H. E. Jones said, although no pro-
fessed electrician, he had nevertheless
been struck with what seemed to him to
be two fallacies in the paper. First, the
author appeared to assume that there
was a distinct ratio between the heat
units observed and the amount of light
given. That was certainly contrary to
his experience of photometric experi-
ments with other lights. In fact, with
regard to gas lights it was exactly in the
inverse ratio, for the most heat from gas
light was coincident with the worst illu-
minating power. That part of the paper,
however, with which he found most fault
was an error in the statements which had
been made from time to time about the
electric light and which in his view dis-
credited those connected with it. An at-
tempt was made to draw a comparison
between the cost of electric light and
that of gas, but in estimating the cost of
the electric light the author stopped
short at the HP. cost of production. In
the appendix to the Report of the Elec-
tric Light Committee, June, 1879, p.
243, it was stated that of the total cost,
37.11 francs, of a certain number of
lamps, something like 31 francs attached
to the carbon, altogether independent of
machine and HP. In the present case
the author had taken the cost of gas at
2^ dollars per 1,000 cubic feet in New
York, and to compare the cost of the
electric light with that, there must be
added expenses of distribution, manage-
ment, wear and tear of machinery, and
interest upon capital, which altogether
was no very small item. The published
accounts of a large Metropolitan Gas
Company showed that the rates and
taxes, the collection and the making up
of the accounts in the office, the distri-
bution expenses, cost of inspecting the
lighting, and so on, came to three quar-
ters of the net cost of material for the
gas, deducting the product received from
the coal used. "When the advocates of
the electric light had obtained a busi-
ness, which they had not at present, they
would be confronted with these ex-
penses ; they would also be confronted

with the dividend payable to their share-
holders, which would have to be met
by a balance at the bank, and not by bills
and promissory notes, paid for the as-
sumed privilege of lighting some other
part of England with a light which, as
shown in London, made outsiders think
that it was a commercial success. It had
been shown in the streets of London;
the misguided foreigner came over and
thought that the city was being lighted
in competition with gas in the most suc-
cessful manner ; the figures of cost were
kept out of sight ; and the foreigner went
and bought a concession of some patent
for electric lighting. That was a profit-
able operation. He did not wish to
wander from the precise subject, but he
spoke essentially as a gas engineer. It
was said when the electric light was first
brought into London that there would
be seen on the Embankment lights of
1,000 candle power, but what was the re-
sult ? It was found, when tested with
the photometer by Mr. Keates,* that the
light was only 150 candle power. If any
gentleman drove over London bridge on
a dark night he would find the passage
a difficult one ; he had made it constantly
for the purpose of observing the electric
lighting, and the conclusion in his mind
was that the lighting of some parts of
the city now, practically by the Electric
Light Companies, was a ghastly failure.
That it was a very extravagant one was
proved by a document printed by the
Common Council, showing the tenders
for electric lighting in the City of Lon-
don, and proving that it was costing for
current expenses three or four times as
much as gas ; and when the expenses of
wear and tear, and so forth, were added,
it would be seen what a costly thing
electric light was. The author appeared
to have written the paper for the pur-
pose of bolstering up the electric light
at the expense of gas, and claimed for
it that which Mr. Jones did not hesitate
to say, and which every one practically
acquainted with the carrying on of a
commercial undertaking on a very large
scale would know, was only a fraction of
the cost, viz., the HP. of developing the
light. No confidence could be reposed
in such a comparison. There should
have been added the carbons, the wear

* Vide Report to Metropolitan Board of Works, Ma y,
1879, p. 11.

CANDLE POWKi: OF THE ELECTRIC LIGHT.

:*9

and tear of the machines, which were
running eight hundred revolutions per
minute, the original cost of the plant,
the depreciation, which, with machinery
running at that Bpeed, was 15 to 2D per
cent, per annum, and also the managerial
and general expenses, which, as shown in
the case he had quoted of a Metropolitan
Company, where the rates and taxes alone
amounted to 30 per cent, of the net cost
of the gas for coals, after deducting the
value of the products. One other point
he wished to notice was this ; a great
deal had been said of what light could
be developed from 1 lb. of coal burnt on
the bars of a steam engine developing
electric light, and it was assumed that
that was something enormous compared
with what the gas engineer made of it.
Now he wished to say that 1 lb. of coal
could not be treated more economically
than by the gas engineer. He took it,
distilled it analytically, brought out the
fixed, gaseous, and liquid carbons, and
then returned a fuel out of the coal
which was essentially the fuel of the
poor ; and besides that, he got the light,
and many other things. There had also
now been obtained something approach-
ing to a good gas engine, and it had been
found that gas used in that way was
really more effective than the coal burnt
under the boiler. Therefore all the ex-
aggerated contempt that was poured by
ignorant people upon gas, as contrasted
with the electric light, was very much
misplaced. There was much ignorance
abroad; he was guilty of it himself to
some extent with regard to electricity.
As he had frequently replied to people
when they had asked him upon the sub-
ject, electricity, as applied to lighting
and to power, was analogous to water
which was pumped into an accumulator
under pressure, and liberated through
the crane or other machine, being a
transmitter of energy and not an origi-
nal power, which could be gathered any-
where, and turned at once to the service
of man. He would like to direct the at-
tention of the members to the article on
the subject of the cost of Electric Light
in The Engineer of the 13th of January,
1882.

Mr. R. E. Crompton observed that it
had been pointed out how engineers could
obtain a cheap source of power by using
the gas engine, and their attention had

been called to the point, that with the
primary object of supplying the public
with light, by means of gas, the manu-
facturers obtained secondary products of
importance, quite equal to, in fact, al-
most greater than the gas itself. He
thanked Mr. Jones for this; in future
electric light engineers would be able to
obtain all the useful residual products
from their lb. of coal by the ordinary
process of distillation, and simply use the
gas as a means of obtaining motive
power for producing the electric current.
He had, however, prepared a few notes
on a different part of the subject, namely,
the purely scientific question "of the candle
power of the electric light. He noticed
that almost at the commencement the
author confessed that but little was
known of the specific heat of the vapor
of the electric arc and of its temperature.
This admission had greatly disappointed
him, as from his own observations he
had long since formed an opinion that
the candle power of the electric light,
whether the arc light or the incandescent
light, was a function of, or at all events
closely allied to, its temperature, and
from the title of this paper he fully
hoped for some information on the point.
In incandescent lamps the relation of
temperature to lighting power was self-
evident, as the temperatures were com-
paratively low, and the changes in color,
marking the changes in temperature,
could be followed by the eye. But with
the arc light it was different. The
greater intensity of the light made it
difficult, and almost dangerous, to ob-
serve it closely, and it was only by the
use of the spectroscope, or by similar
means, that changes of these exalted
temperatures could be observed. The
author had unnecessarily complicated
the matter by introducing the regulating
arc lamps themselves. They occupied
but a secondary part in obtaining high
efficiency in candle power from a given
electric current. So long as they held
the carbons firmly in line, and fed them
together with due regularity, so as to
maintain a constant difference of po-
tential on the two sides of the arc, they
did all they could towards this efficiency.
What had mainly to be looked to was the
obtaining of a higher temperature at the
arc, and this by perfecting the carbon
rods. The carbon rods must excel in

VAN NOSTRAND'S ENGINEERING MAGAZINE.

City of of London — Electric Lighting, 1880.

Abs#act of tenders received by the Streets Committee of the Commissioners of Sewers on the
28th day of October, 1880, for lighting the thoroughfares of New Bridge Street, Ludgate
Circus, Ludgate Hill, St. Paul's Churchyard (North side). Cheapside, Poultry, Mansion House
Street, Royal Exchange (open space in front of), King William Street, Adelaide Place, Queen
Street, Queen Street Place, Queen Victoria Street, King Street, Guildhall Yard, London Bridge,.
Southwark Bridge, and Blackfriars Bridge.

District No. 1.— Comprising Blackfriars Bridge, New Bridge Street, Ludgate Circus, Ludgate
Hill, St, Paul's Churchyard (North side), and Cheapside (trom Western end to King

Street):—

Name of Contractor
Tendering.

Anglo-AmericanElec-
tric Light Company
("Brush" System).

Crompton & Co

Electric and Magnetic
Company ( ' ' Jabloch-
koff" System.)

Siemens Brothers

To light for
12 months,

from Sunset
to Sunrise.

660 abt.

(same price as

Commission

pays for gas.)

2,007

1,500
2,050

To provide andj
fix Machinery, j Total
Lamps, &c, and Cost of 12

remove same at

expiration of

Contract.

Months'
Trial.

750

500
1,550*
1,650

1,410

2,507
3,050
3,700

Number of

Electric

Lamps to be

Lighted.

(viz. , 23 small,

6 large.)

Numberof
GasLampsnet
to be Lighted
when Electric

Lamps are
alight.

150 abt. = 600

152
144

144

-608
=576
-576

District No. 2. — Comprising Southwark Bridge, Queen Victoria Street, Queen Street (between
Queen Victoria Street and Upper Thames Street), and Queen Street Place : —

Anglo- AmericanElec- )

trie Light Company >

....

No tender.

("Brush" System). )

Crompton & Co

2,167

560 •

2,727

176

= 704

Electric andMagnetic )

Company ("Jabloch- >

1,580

1,350*

2,930

161

= 644

koff" System.) )

Siemens Brothers

1,850

980

2,830

(viz., 26 small,

5 large.)

164

= 656

District No. 3. — Comprising London Bridge, Queen Street (between Queen Victoria Street and
Cheapside), Cheapside (oetween King Street and Poultry), King Street, Guildhall Yard,
Poultry, Mansion House Street, Royal Exchange (open space in front of), King William
Street, and Adelaide Place : —

Anglo-AmericanElec- )

trie Light Company v

....

No tender.

•

(" Brush " System). )

Crompton & Co

2,475

650

3,125

132

=528

Electric andMagnetic )

Company ("Jabloch- V

....

No tender.

koff" System.) )

2,270

1,450

3,720

(viv., 26 small,
6 large.)

138

=552

* Should the Commission determine to have the conductors laid underground, the additional cost for each
district will be £2,000 and £2,000 more for removing them and making good after.
N. B— The black figures are not in original, but represent about the cost of the gas lighting.

CANDLK POWEB OF THE ELECTRIC LIGHT.

two main points; lirst they must be i
tremely refractory and infusible, in other
words, be pure, and free from even the
smallest percentage of materia] more

-ily volatili/.able than the carbon itself.

sondly, they must be hard, dense and
compact, so as to oppose as much iv
ristance to the disintegrating action of

the current as possible, thus necessita-
ting the much desired extreme tempera-
tores. The wide discrepancies noticed
between different photometric measure-
ments of the same electric light system
were mainly due to the differences in
purity and density of the carbons. Pure
carbons of little density, or dense car-
bons containing considerable impurity,
were equally adverse to nigh candle
power. Carbons had been moulded from
absolutely pure carbon, yet of loose tex
ture, which would not afford anything
more than a pale blue light of 50 or 60
candles, when a 20 ampere current was
used, and almost equally bad results had
been given by well-made dense rods, con-
taining not more than 5 per cent, of
lime, soda and other ash. Moreover, the
same rods varied considerably from inch
to inch, and this would often account for
the great changes in brilliancy observ-
able in the arc lights in public use. The
blame for the variation in the light was
generally visited on the lamps, machines
or engine, but now-a-days the blame ought
to rest far oftener on the carbons alone.
If, as they burnt away, a point was
reached where the purity and density
exceeded the average, the temperature
and the light were greatly increased,
and a corresponding decrease in purity
or density would greatly diminish the
temperature and light. The light given
by a pair of carbons in an arc lamp would'
vary 60 to 100 per cent, from this cause
alone. This change in the light-giving
efficiency during the burning away of a
single pair of carbons, and consequent
wide fluctuations in the photometric
readings, had been the cause of endless
trouble to observers. The generator of
the current, the lamp, the photometer,
the difference of color between the arc
light and the standard light, and lastly
the observer himself, had all been ob-
jected to. It was uncertain what the
author meant by " axial " and " bi-axial "
measurements. Probably, however, he
meant what was ordinarly termed hori-

zontal and angular measurements. A

strong protest ought to be raised against
the absurdity of taking horizontal photo-
metric measurements* of continuous-cur-
rent arc lights. There was no reason
why experimenters should continue mak-
ing and publishing them without the cor-
responding angular measurements, un-
less it was that the latter were a trifle
more difficult to obtain ; but even that
could be easily avoided by inclining the
lamp when taking the photomeric read-
ings. At any rate, the commercial effi-
ciency of the light was always taken at
the angular measurement, for the simple
reason that as all large centers of light,
such as electric arc lamps, must be placed
high up, in order to avoid floor shadows,
the rays below the horizontal plane were
of the greatest commercial value. This
angular measurement was at least 80 per
cent, in excess of the horizontal one, and
it was eminently unfair to compare the
electric arc, measured thus horizontally,
or at its point of lowest commercial
efficiency, with the incandescent electric,
or any other source of light, the efficiency
of which was nearly equal in all direc-
tions. The introduction of heat-units
into calculations of the candle power effi-
ciency of the lamps seemed to be unwise,
and likely to lead to confusion. Surely
the expression "candle power per HP."
was sufficient to compare the lighting
power with the energy. Talking of
" Gramme degrees per candle power "
seemed like saying " minutes per ounce."
In the table where the arc lamps were
compared with incandescent ones, the
arc lamps were deprived of the 80 per
cent, due to the angular measurement
not being taken, whereas the average
candle power of the incandescent lamps
jwas put at 271 candles per HP., instead
of 180 candles, which was certainly the
maximum efficiency obtained from such
lamps up to the present time, under
1 actual conditions of safe working. With
these corrections the efficiency of the
arc lamps, compared with that of the in-
candescent ones, became as 18 to 1. Wide
1 as this gap was, it could not be hoped
materially to lessen it, considering that the
temperature of the arc carbons was that of
disintegration and destruction, whereas
that of the incandescent lamps must not
be sufficient to soften, or even change, the
form of the delicate carbon filaments.

VrA]^ nostraistd's engineering magazine.

THE BIRMINGHAM AND EDMONTON SEWAGE WORKS.

By THOMAS COLE.
A Paper read before the Civil and Mechanical Engineers Society.

Prom "Iron."

Having visited the sewage works of
Birmingham last year, and collected
some information thereon, I venture to
lay the same before this society, believ-
ing that it may prove of interest to many
who may be unacquainted with the place
and circumstances, and further give rise
to a discussion at once valuable and in-
structive. The population of Birming-
ham in 1861 was 296,076 ; in 1871, 342,-
505, and in 1881, 402,296. The suburb-
an districts of Birmingham, viz., Hands-
worth, Aston, Saltley, Balsall Heath,
Harbone, and Smethwick together give
an additional population of 150,000.
The lowest point of the borough is at
Saltley, where the sewage farm is situ-
ated, and this is at 290 feet above mean
sea level. The highest point is on the
Hagley road, which is 610 above the
same datum. At Birmingham one has
the advantage of seeing ^wo systems of
dealing with the sewage in operation :

First. Precipitation by^ the lime pro-
cess ;

Second. The intercepting, or dry sys-
tem ;

and I do not think that there is any
other town where one would find the de-
tails of the two systems carried out to
such perfection or where so large an
amount of money has been spent or so
much energy expended.

To better understand the present posi-
tion, it is necessary to glance at the his-
tory of the difficulties that the authori-
ties have had to overcome in the disposal
and treatment -of the sewage, and it may
be said that in scarcely any other in-
stance has a local authority bestowed
more pains to ascertain what was the
right system to adopt than the authori-
ties of Birmingham. In the first in-
stance, the sewage was discharged direct
into the River Tame, a small stream
which at a few miles from the works
flowed through the estate of Sir Charles
B. Adderley. In 1855 we find the bor-
ough surveyor presented a report recom-
mending irrigation. Sir Charles Adder-
ley complained of the nuisance caused in

the river by the sewage, and in 1858 on
his application an injunction was ob-
tained to restrain the corporation from
discharging sewage into the Tame ; but
the Court, in granting it, accorded time
in which the corporation were to con-
struct works to abate the nuisance. In
1859 two subsidiary tanks were con-
structed near the main sewers, and puri-
fication by sand filtration and by upward
and downward filtration were severally
tried and abandoned. In 1861 the cor-
poration purchased, at a cost of £8000,
28^ acres of land, in order to obtain ac-
cess to canal and railway, and for afford-
ing additional facilities for dealing with
the mud arrested in the tanks. In 1866
Sir Charles Adderley again complained
of the state of the river, and the corpora-
tion in 1867 took on lease 118 acres of
land in addition at a yearly rent of £855,
with the object of cleansing a portion of
the sewage by irrigation. They caused
this farm to be laid eut, leveled, and
drained, and the necessary roads and
bridges, to be constructed, at a cost of
£11,250, or at the rate of £750 per acre ;
but an order of sequestration was ob-
tained in 1870, and another injunction
was obtained by Sir C. Adderley, and by
owners of property for the purpose of
preventing the accumulation of sludge
near the subsidence tanks ; further ac-
quisition of land was then attempted and
failed. In 1871 the Town Council being
alive to the defects of the system then
adopted, and having an additional stimu-
lus to action by the injunctions obtained
against them, appointed a committee to
report on the best means of dealing with
the sewage of the town. This commit-
tee presented a valuable and exhaustive
report, and recommended the taking of
2500 acres of land near Kingsbury, about
eight miles below the present outlet, and
amongst other observations and conclu-
sions passed severe strictures on the
lime process. The recommendations of
this committee were considered too
costly and the whole question was again
referred to a special committee, and on

THE BIRMINGHAM AXI> EDMONTON SEWAGE WOBK8,

4:*

their advice the council promoted a Bill
in session 1872 to acquire powers to ex-
tend their main sewer to Kingsbury and

there to obtain 800 acres of land. This
Bill was thrown out on the third read-
ing, and it cost .£10,000, leaving the coun-
cil still in a dilemma. However, to sat-
isfy the requirements of the Court of
Chancery the corporation purchased
twenty-four acres of land at Saltley for
£8000, and further added to that farm
by adding to it a purchase of .101 acres
at a cost of 29,400. Notwithstanding
the committee's report above referred to,
the lime process was adopted by Mr.
Hawkesley, who, with Mr. Hope, V.C.,
prepared a scheme for the requirements
of the town, and their recommendation
being adopted, four additional sets of
subsidiary tanks were constructed, to
which another large tank has recently
been added. In 1877 the order of se-
questration was discharged. At this
date, notwithstanding the expense incur-
red by the corporation in clarifying
their sewage prior to its discharge into
the River Tame, the sewage of adjacent
townships with large and rapidly increas-
ing populations was being poured daily
into the Tame or into its tributaries
without any attempt at clarification. It
was therefore resolved to combine under
the powers of the Public Health Act,
1875, and the Birmingham Tame and
Ilea United District Drainage Board was
formed and confirmed by Parliament in
the following session. The total popu-
lation of this district is estimated at
about 550,000. To meet the additional
strain thus thrown on the works the
board in 1880 entered into negotiations
for the purchase of 867 acres of land at
Castle Bromwich, to be used for irriga-
tion from the effluent from the tanks,
and in April, last year, the Local Gov-
ernment Board after an inquiry, granted
powers to borrow £188,000 for addi-
tional land and works.

The Saltley farm, the position of which
is shown in red on the plan, has now an
area of 272 acres, the subsoil of which
is generally of a gravelly nature, with oc-
casional patches of clay. There are three
large tanks and sixteen smaller ones,
having an aggregate capacity of about
7 J million gallons. The amount of
sludge deposited in the tanks in 1880
was 178,400 cubic yards, or about 490

cubic yards per day, and required an
net o\' 53j acres of land for digging in
(ho same, or rather more than an acre a
wreek. The average dry weather How of
sewage is about thirteen million gallons
per day, the population actually contri-
buting this amount being estimated at
about thirty gallons per head. The lime
is slacked and ground with water, and
mixed wTith sewage on its arrival at the
works, and rather over thirteen tons of
lime are used a day.

The sewage next passes through the
nineteen depositing tanks with a velocity
of about 30 feet per minute through the
larger tanks and a little less through the
smaller ones. In these tanks the sewage
residuum varies in amount and density
in proportion to the distance of the tanks
from the sewer outfall. The clarified ef-
fluent is then allowed to pass by various
outlet sluices into the rivers Rea and
Tame, or is disposed of by irrigation on
the corporation land. The following is
the analysis of the effluent taken from the
Local Government Report on the Sew-
age Disposal 1876, p. 36 :

Chemical Laboratory, Corporation Sewage
Works, Birmingham. Certificate. Sample
of effluent water from new precipitating
tanks at above, March, 1875. Examined
for general impurities. Copy, Jan., 1876.

Grains per
imperial gallon.
Total solid residue containing. .58.10

Mineral matter 57.10

Volatile matter 7.00

Suspended matter 1 . 68

Soluble matter 49.42

Silica matter 0.84

Alumina oxide of iron and phos-
phates 0 . 14

Lime 12.22

Sulphuric acid 17 . 38

Chlorine 9.52

Free ammonia 1 .218

Albuminoid ammonia 0.042

Disintegrated animal refuse 0.420

Appearance clear

Smell Slightly ammoniacal

Action on test paper Alkaline

Judging from the appearance of the
effluent at the time of my visit, I have no
hesitation in saying it was of a charac-
ter which should not be allowed to go
into any river. The sludge is lifted from
the tanks by an elevator, and, by means
of an elevated trough-carrier, run into
beds about 8 yards square, to a depth of
about 18 inches, and allowed to drain for
a week or two. It is then dug into the

van nostband's engineering magazine.

earth and covered with soil. Plowing
was, for some time, tried, but digging
was found to be the only efficient means
of amalgamating with the soil. The
land is thoroughly drained, and this
greatly facilitates the dealing with the
sludge. These drains bring the effluent
back to the subsidence tanks. The
sludged land is very favorable to the
growth of the cabbage and mangold ; as
much as 60 tons per acre is obtained of
the latter. The valley of the Saltley
Farm is, however, an excessively cold
one, consequently market gardening is
not as successful as it otherwise might
be, as the crops are late. Of all crops
that thrive best on sewage, Italian rye-
grass yields the best results, but the de-
mand for this has not been large. No
nuisance arises from the present method
of dealing with the sludge. The bor
ough surveyor states that there are no
complaints received from the three
thousand houses thit are within half a
mile of the farm. The cost of dealing
with the sludge (lime, labor, &c, but ex-
clusive of sinking: fund on capital) was
£12,356 per annum, or Is. 4^d. per cube
yard of sludge. Owing to the sharpness
of the gradients, and the 'large propor-
tion of macadamized roads, much of the
detritus is carried to the tanks. A small
proportion of the sludge was some time
ago experimentally converted into cement
by General Scott's process, but it was
not done to any great extent, and I saw
nothing of it at my visit. From the
statement of income and expenditure for
1875 and 1876, it does not seem to have
been successful, the expenses for the first
year of the process being £332, and the
income £179, while from the second
year the expenses were £300 and the in-
come £150. It is said by some that the
lime process as used at Birmingham is
merely a temporary means pending the
adoption of some more substantial and
efficient mode, but the permanent and
expensive character of the works tend to
preclude such a possibility. The new
farm is not yet laid out, but it is intended
to connect it with the Saltley farm by a
conduit about 2| miles long and 8 feet
internal diameter. The land is of a very
favorable nature and contour, the sub-
soil being nearly all sand and gravel, and
of such a level that 800 acres or nearly
the whole may be brought under irriga-

tion by gravitation. It is proposed to
lay it out for broad irrigation, except
about 40 acres, intended as an intermit-
tent filter bed for use in cases of emerg-
ency. About 648 acres will be freehold,
and the remainder leased for long pe-
riods. It is favorably situated for dis-
posal of produce, being within an easy
distance of Birmingham, by which it is
well connected by road, canal, and rail.
Owing to the acids contained in the sew-
age from the various galvanizing and
other works the liming will still be con-
tiued after the new farm is in work, but
probably to a less extent, and a consid-
erable amount of sludge now intercepted
in some of the tanks will be carried on to
the land with the effluent. •

General Remarks on the Lime Pro-
cess.— The Rivers Pollution Commission-
ers in their first report at p. 52 say, in re-
ferring to the lime process at Leicester,
Tottenham, and Blackburn, " In all
these places the plan has been a con-
spicuous failure, whether as regards the
manufacture of a chemical manure or
the purification of the offensve liquid.
And further, " the method obviously
failed in the purification of the sewage
to such an extent as to render it admis-
sible into a river." It is supposed by
some that the effect of this and other
chemical processes is not only to purify
the sewage but to give to the effluent
water a manuring principle non-polluting
in itself. This, however, is not the case,
with the lime process at least, for the
fertilizing power of the effluent is not
due to any innocuous manurial principle
which is added, but rather to the pres-
ence of the nitrogenous organic matter
which it has failed to abstract. There is
this, however, to be said of the lime pro-
cess that it is the simplest and least
costly of any ; and it may, perhaps, be
said also that the sewage of Birming-
ham, containing as it does such an abund-
ance of acid metallic salts, is peculiarly
suitable to be treated by this process.
On the whole, the Saltley works reflect
considerable credit on the borough en-
gineer, by whom they have been designed
and carried out ; kept in excellent order
and complete in themselves, they are an
evidence of the public spirit shown by
the corporation of Birmingham, and will
amply repay a visit to any who take an
interest in this branch of sanitary en-

THE BIRMINGHAM AND EDMONTON SEWAGE WORKS.

gineering, as they offer as good an ex-
ample of the kind as probably any in the
country.

The Intercepting or Dry System.—
We now come to the description and the
consideration of the " dry process," as
carried out in Birmingham, at wharves
situated at Rotten Park Street, Shad-
well Street, and Montagu Street; the
latter, which I visited during last sum-
mer, is by far the most important of the
three depots. The works at Shadwell
Street have, I believe, been partially, if
not entirely discontinued, on account of
the proximity to the General Hospital.
The pail system wras established here in
1872, with a view of combating the diffi-
culties met with from the Chancery pro-
ceedings above described, arising from
the treatment of the sewage from Salt-
ley works. It wras, accordingly, thought
desirable to adopt the intercepting or
pail system, in addition to the lime pro-
cess then in operation. The pails with
their contents together with the miscel-
laneous contents of ash-pits, are collected
weekly, and about 1100 tons of pail con-
tents, are disposed of weekly at the
three depots, 466 tons of which repre-
senting the contents of about 1700 pails
together with 506 tons of ashes col-
lected from the premises where these
pails are 'in use, are disposed of weekly
at Montagu Street wharf. The super-
intendent of the department states the
number of pans in use in the borough
on the 31st December, 1880, was 31,-
935, and that the carrying out of the
work involved the collection, during the
year, of 1,621,360 pans and 69,256 loads
of ashes. At the Montagu Street works
there is an engine house, and two 25
horse-power engines ; stack, 260 feet
high ; three multitubular and two Gal-
loway boilers, the latter being 27 feet
6 inches long and 7 feet 6 inches high,
averaging 60 horse-power each, and
three of Firman's dryers by Messrs.
Alliott & Co., of Manchester, and two by
Messrs. Forrest, of Manchester. The col-
lection takes place at night, between the
hours of 10 p.m. and 10 a.m., by means
of vans or wagons of a somewhat pe-
culiar construction. They are about 13
feet long, and are divided into two
compartments, the foremost taking the
pails, and fitted with doors closing
hermetically, so preventing the slight-

est escape of smell, and having a ca-
pacity sufficient to carry 18 pails, while
the rear portion contains the dry ash-
pit refuse. This portion of the van
is open and hopper shaped. The van,
when loaded, weighs about 3£ tons, and
is drawn by one horse, special provi-
sion having to be made to assist the
traction over certain hilly portions of
the town. The vans are so made that
they can be easily washed with water
from side to side. This is done every
day, as soon as their work is finished.
They are then left with both sides
open for the air to play through
them and do its part towards keeping
them inodorous. The pails are of gal-
vanised iron, cost 10s. each, and are fur-
nished with a well-fitting lid, formed by
an elastic washer under the lid, which is
kept tight on to the top edge of the pan
by the spring on the lid. The spring has
a hook at each end, which catches on the
hoop round the top of the pan pressed
by the spring. The lid makes, with its
india-rubber washer, a water-tight joint,
and thus hermetically closes it, and so
preventing any escape of offensive smell
and consequent nuisance during collec-
tion. These pails, if brimful, would hold
about 14 gallons, but on an average they
take about 10 gallons. They are most
carefully cleansed, and perfectly disin-
fected previous to their being sent out.

Most of the poor of Birmingham live
in courts, the privies are grouped to-
gether, and generally placed in the least
conspicuous position. On its arrival at
the works the van stops at the foot of a
gradient of 1 in 15, when a chain is
brought down the incline and attached
to the shafts, and thus, with the help of
steam, the horse with its load walks up
the hill without the least exertion. Ar-
riving at the summit the van is now in-
side the building, the chain is unhooked
from the shafts and the horse takes the
van down a passage, stopping at a large
cast-iron tank, into which the pails are
emptied by hand ; the horse then moves
a little further and stops the van over a
trap door in the floor, and through this
door the contents of the rear compart-
ment of the van, the ash-pit refuse, now
falls to the floor below, which is the level
of the wharf side. Here proceeds the
busy operation of sorting. All descrip-
tion of material, such as stones, bricks,

VAN NOSTRAND S ENGINEERING MAGAZINE.

brickbats, and such like, are put into
barges and go away to tips. Old iron of
every shape and description is sold to a
contractor. Kags are picked out and
sold, and paper too. Meat and other tins
at one time presented a considerable dif-
ficulty, but they now find a purchaser
who deprives them of the tin and then
sells the remaining iron. When the
larger materials are taken out, the refuse
is thrown into revolving screens ; these
yield sifted stuff which, being mixed with
a portion of the filthy contents of the
tanks I have mentioned, is carted off and
sold as manure. The cinders and every-
thing combustible goes to the furnaces
under the boilers which generate the
steam necessary for the manipulation of
the works. The sewage is now put
through the Driers, sulphuric acid being
first added to it in the proportion of 30
lbs. per ton, for the purpose of fixing the
ammonia. These driers consist of a
steam-jacketed cylinder, into the interior
of which the pail contents are thrown, and
the sewage is kept in motion by revolving
hollow arms, through which steam is
driven. The shell spindle and arms
thus radiating at a high temperature, in
combination with the mech*anical action,
accomplishes the end in view. The va-
por is then drawn off by means of an ex-
hauster, is afterwards condensed in a
Liebig's condenser, and the liquor is
passed into a drain, which discharges it
into the adjoining river. To avoid this
an experiment is being made to pass the
offensive liquid through a filtering
medium, which, if successful, will be
permanently carried out. These drying
machines reduce one ton of sewage to
two cwt. three qrs. two lbs., showing that
about ll-12ths of the pail contents is
only water. The operation of drying one
ton is performed in 14^ hours, and the
residue, called " poudrette," is extracted
from the bottom of the cylinder by means
of a door made to open for the purpose.
It is then put into sacks and sold to
artificial manure merchants at £8 per
ton.

Mr. Councillor Martineau, to whose
courtesy I am greatly indebted for much
information concerning the dry or inter-
cepting system, in speaking of Forrest's
driers, says : " We continue to be
thoroughly satisfied with the two we
have of his make. Our expenditure this

year is so much below our estimate that
we are buying a new machine out of part
of the surplus. It is of a different form
from Forrest's ; I will not say anything
about it until we have tried it. If it is
as successful as we hope, we shall, early
in the year, ask the council for a very
large sum of money to enable us to make
poudrette of all the pail stuff taken to
Montagu Street. The total cost of re-
moval of night soil and the collection
and disposal of the house refuse in 1880
amounted to £42,996, and the total re-
ceipts from the sale of the different prod-
ucts amounted to £7,694 lis. 8d., which
leaves a sum of £35,297 5s. 9d., as the
net cost to the borough of Birmingham.
It is contended in defence of this sys-
tem that it tends to isolate contagious
diseases, inasmuch as the fcecal matter is
kept from spreading its poisonous germs,
as would otherwise be the case in the
common sewer, and as a practical proof
of the sanitary improvement of the town,
it is pointed out that the death rate at
the date of the introduction of the pail
system in 1872 was 24.02 per 1,000 in-
habitants, and 5.2 of these deaths were
due to zymotic diseases, whereas the
death rate now stands at 21.49 per 1,000,
and of these only 3.2 were due to zymo-
tic diseases. There is no doubt that in
India and other places where the water
supply is often not plentiful, and the
question of sewage disposal presents
great difficulties, the systematized pail
system would afford great advantages.
It is further urged that the use of pails
is eminently suitable to those tenements
where the water-closet system is care-
lessly or wilfully abused, and the appa-
ratus is constantly getting out of order ;
and owners of these properties hail with
favor the adoption of the system as an
immense saving to them. Unquestion-
ably this kind of property presents a
good deal of trouble to effectually deal
with their sanitary arrangements, and I
would draw your attention to a form of
closet to utilize the waste water of a
house for flushing purposes, called "Fow-
ler's closet," which has been found ad-
mirably suitable to places where no other
has been found to answer. The system
appears simple, and has been adopted in
several towns with the most satisfactory
results, the surveyors to the different
localities speaking of it very highly. The

THE BIRMINGHAM AND EDMONTON SEWAGE WORKS.

surveyor to the Local Board of Felling
says : " I consider it a boon to the pub-
lic at large, more especially to the work-

as an appendix to this paper : — The Ed-
monton Sewage Works are situated about
a mile from the town, and close to the

ing classes, it being a simple and efficient main line of the Great Eastern Railway,
arrangement, and further, there is no The population in 1877 of the district
machinery, consequently it is most suit- ' was 15,000, and that provided for at the

works 60,000. The area of the district
is 785-4 acres, or about 12 square miles.
The area of the sewage farms is 114
acres, of which 8 acres are used as a
downward filter planted with osiers.
Twenty-one acres are used for irrigation
purposes, and the remainder is let to
farmers. The sewage is treated on its
arrival at the works on a modification of
the lime process known as Hille's system,
in which lime is the chief precipitant, the
patent consisting in the addition of mag-
nesium chloride and tar. The sewage,
varying from 80,000 to 100,000 gallons
per day, is brought to the outfall works
by a 3-feet 6-inch sewer, first passing
through a screen in a penstock chamber,
which separates the larger materials ; it
then enters a second chamber, from
which it may at pleasure be let out dir
rect on to the land without entering the
depositing tanks. A 10 horse-power
steam engine here works a Gwynne's
centrifugal pump, and regulates the ne-
cessary amount of disinfecting material
which is added. The sewage then flows
into a collecting reservoir which is un-

able for tenement and working-class
property.'' Being simple in construction,
it is quite impossible for the system to
get out of order. There is no expense in
obtaining towns water, as all the slops
and refuse water from the house and
yard pass through the closet. There is
not the slightest smell or nuisance where
these closets are adopted.

Returning to the dry system, the au-
thor has only further to state that at the
annual congress of municipal engineers
held in Birmingham last year the mem-
bers of that association very warmly con-
demned the system as dirty and demor-
alizing. The royal commission appoint-
ed to inquire into the drainage of Dublin
says of the pail system : " That the col-
lection of the city excreta by means of
movable pans, or by the process of so-
called dry conservancy, will cause more
nuisance and be more costly than water
carriage. The nuisance will be greater,
because there will be a retention of the
excreta on the premises, and the cost
will be greater by the amount of labor
necessary to collect the excreta, and also

because there is no practical mode of j derground, built in brick and roofed in,
converting the excreta into a portable | and capable of holding two million gal-
manure which will pay the incidental j Ions ; from here it is lifted into the de-
charges." Mr. Rawlinson says his views ! posit tanks when precipitation is carried
respecting Dublin equally apply to every \ out. The pumping, mixing, and supply
other town in the country. One of the in- j of chemicals is performed by two 14-inch
pectors of the Local Government Board [ pumps worked by two 10 horse-power
has said, however, that the works at engines contained in an engine-house,

which include the machinery and the
mixing apparatus. The sewage is lifted
and delivered from the reservoir into an
iron cylinder 5 feet high by 5 feet in

Montagu Street, which I have described
to you, and which he visited, were, and
would be, a success. The system is ad-
mirably carried out, and, as far as circum-
stances will allow, wonderfully free from diameter. In this cylinder sewTage and
offence. disinfecting compound meet. Another

The Edmonton Sewage Works. — cylinder of like dimensions, fitted above
Some of the members of this society that which receives the sewage, contains
visited these works last summer, and our an agitator which is driven from the en-
numbers being few on that occasion, gines and holds the disinfecting corn-

there must have been many who were
unable to avail themselves of the excur-
sion, and it is with the idea that some de-
scription of what we saw may prove of
interest to the absentees on that occasion
that I venture to put before you the fol-
lowing notes, not out of place, perhaps,

pound ; this has to be dissolved in, and
diluted with, sewage, as no pure water is
available. The three deposit tanks are
built in concrete above ground ; they
are side by side, and divided by two con-
crete walls. Each tank is 200 feet long,
30 feet wide, and 7 feet deep, with the

VAN NOSTEAND'S ENGINEEKING MAGAZINE.

bottom of each sloping towards its centre
with an outlet pipe, through which the
sludge is emptied by a subterranean
channel to the sludge beds. The
sludge bed is about 150 feet long,
30 feet wide, and has an aver-
age depth of 2 feet 6 inches. The sludge
may be deposited here when not wanted,
or it may be delivered at the penstock
chamber before alluded to, and to which
it is conveyed by an open channel. At
the date of the visit there seemed to be
some difficulty in getting rid of the
sludge as the beds were full, and bore
the appearance of having been full for
some time, but I \am informed that there
are now three sladge beds in use at these
works, and these are used alternately.
When one of the beds is filled the mois-
ture is drained off, and the sludge is re-
moved and used by the farmers as
manure. They fetch it in carts, and pay
some 2s. to 3s. per load. There is no
accumulation of sludge at all now, as the
stuff is produced and removed from the
tanks, the sludge beds are filled and used
in rotation. The demand for the sewage
manure is considerably increasing since
the quality and its value have become
appreciated. The osier beds occupy an
area of about eight acres, they are
underdrained some three feet deep, and
are said to take some two or three days'
sewage running. They were not in use

at the time of the visit, the various sew-
age channels being dry, caked hard, and
generally neglected. The growth of
these osiers is, nevertheless, stated to be
a success, and the first year's growth is
reported to have yielded a profit. To
return to the tanks. These are so ar-
ranged that they may be used singly or
all three at the same time, the water
passing from the first into the second,
and when these are full from the second
into the third tank. From the overflow
of the third tank the effluent water pass-
es either direct into the river Lea, after
running along some mile and a half
through ditches, or it may be first pass-
ed on to the filtering beds or on to the
field, 21 acres in extent, used for irriga-
tion, and from here find its way to the
river. There are 10 acres laid out for
water-cress cultivation, which the Board
of "Health let at £10 per acre per annum.
Only the purified effluent is used for
these beds. The quality of the cress is
said to be excellent, and the man who
rents the 10 acres is doing extremely well.
Mr. Hille, to whose courtesy I am in-
debted for much of the information con-
tained in these notes, reports that the
return from the sale of the sludge and pro-
duce of the farm cover to a considerable
extent the cost of the treatment and dis-
posal of the sewage at these works.

THE EFFICIENCY OF SECONDARY BATTERIES.

By E. REYNIER.

Translated from " Comptes rendus de l'Academie des Sciences," for Abstracts of Institution of Civil

Engineers.

Woke; by secondary batteries includes
two phases — the charging of the accu-
mulator by the action of an external
electric source, and its discharge m the
circuit worked. Each of these operations
includes a loss. In seeking the ex-
pression for efficiency, let E0 be the
initial electromotive force of the source,
K0 its resistance, E the electromotive
force of the secondary battery, R its re-
sistance, Ej the difference of potential
at the two extremities of the conductor
worked, Hj the resistance of this con-
ductor, t the time of charge, tx the time
of discharge. The work T0 expended in

charging will be (supposing it to be con-

The work T

E — E

stant) T0=E_° _ t

°R0 + R

utilized in the resistance worked will be

'E2

£,. To find the ratio of these

works, it is necessary to express tx in
function of t. It may be arrived at by
considering that the quantity of electric-
ity Q is the same in the circuits of charge
and discharge (which needs experimental
verification), and that this quantity is pro-
portional to the products of the quanti-

PLATE-WEB GIRDERS.

ties of the currents by the times, whence
the equation

E -E

S2 — ^t=&=

Rft + R

and whence

t =

R + R,

Eo-E
Rft + R

<,«

R + R,

By substitution, the efficiency
T _E '

0 0

The efficiency is thus expressed by the
ratio between the difference of potential
at the two ends of the resistance worked
and the initial electromotive force of the
source of electricity ; it is independent
of resistances and of the values of the
times of charge and discharge. This is
based on the supposition that the work
produced was the heating of a resistance;
if the discharging current actuated a cir-
cuit which was the seat of an electro-
motive force, in an electric motor for ex-
ample, the expression for efficiency would
not be altered. But E, should then ex-

press the contrary electromotive force of
the motor at the origin of the induction.
In practice, the resistances of the cir-
cuits should be taken into consideration.
On account of the low internal resistance
of M. Faure's secondary battery, 80 per
cent, efficiency can be attained with ad-
vantageous conditions of charge and dis-
charge. The constants of the Faure
battery are, for the small size of the 7.5
kilogrammes battery, E = 2.15 volts, R=
0.006 ohm. making E0 - E X 1.1 = 2.36
volts, E,= E 0.9 = 1.93 volts, R0= B=
0.006 ohm, R,=Rx 9=0,054 ohm. The
work expended during charging will be

E 2— EE

—^5 ^=4.24 kilogrammeters per sec-

gr(Jtt0+K)

ond and per couple, which admits of
saturating the battery in a charging time
much shorter than is usual. The work
returned per second and per couple dur-
ing the discharge will be equal to

Ea
/ o ' tS~t~6 -3 kilogrammeters. As to
^(K-t-K,)

efficiency, it is, under these conditions,

^r=^Tzt'> or °1 Per cent-
E„ 1.1

PLATE- WEB GIRDERS.*

From "The Building News."

Although the tendency of modern en-
gineers is apparently to adopt very large
braced girders for bridges wherever pos-
sible— the advisability or necessity of
such immense structures not being al-
ways considered, but rather the hope of
obtaining reputation on the theory that
genius varies directly as the span — by
far the greater number of girders which
are erected in this and other countries are
of the plate-web type.

Several very interesting and elaborate
papers have lately either been read at
the institution or published in the jour-
nals, on the subject of large braced gird-
ers, and the subject has been so thor-
oughly treated, both as regards the
weight of the structures and the strains
due to every possible condition of load-
ing and wind pressure, that little more
need be said on the subject; but the au-
thor would wish, in passing, to call at-

* Read before the Liverpool Engineering Society,
March 29th, 18»2, by John J. Webster, Assoc. M. Inst.
C K

Vol. XXVLL— No. 1—4.

tention to the elaborate and unwieldy
formulae which are given to solve the dif-
ferent questions, and would ask if equally
reliable results could not be obtained by
using simpler and less complicated form-
ulae, which would reduce considerably the
liability to error in the calculations. As
an illustration, the following formula for
obtaining the weight of girders with par-
allel flanges is taken from the paper on
"Girder Bridges," by Mr. Max Am
Ende—

JL__

/ s nl\ D«_lJ (P + M)

^ V0.00213 2/ 2 6 (

^ + (P + M)D2 + (B + l/6M)y^ +W

s .0.0073^ |

0^0213° V(IVl°)(B-6 \

VAN NOSTRAND'S ENGINEERING magazine.

As this formula is simply given to
show its great length, it is not necessary
to explain the different symbols beyond
stating that Q is the weight of the girder
with parallel flanges, with bracing bars
placed at an angle of 45°. Now, sup-
pose that any one using this formula,
after filling sheets upon sheets of fools-
cap, were lucky enough to wade through
its entire length without making an er-
ror in his calculations, would the results
obtained be of such marvelous accuracy
as to repay him for his trouble ? The
author thinks not, and for the following
reason : Suppose a long chain had to
be made to stand a certain load — say,
100 tons ; now, if the links were to
be made of some material which was well
known, such as wrought iron or steel, it
would be an easy matter to calculate very
closely what the size of the links should
be ; and the formula for such a calcula-
tion would be accurate and could be de-
pended upon. But suppose, now, that
instead of all the links being of this
known material, some of them were of a
material about which there was noth-
ing definite known as to its break-
ing strain or other qualities, what
would be the value of the formula then ?
It would be simply valueless. It might
possibly give correct results, but it could
not be relied upon in any way ; and un-
til more is known of the nature of these
mysterious links, an elaborate formula
is simply useless, and would only give
results which may be termed " falsely ac-
curate." Now, the formula quoted is
very much like the chain, and is full of
mysterious links, which at once vitiate
what would apparently be accurate re-
sults. In the first place, the pressure of
the wind is a factor in the investigation,
and what more mysterious link is possi-
ble 1 What is known about the pressure
of the wind, even as to actual pressure,
or as to its local action on large exposed
surfaces ? It is only necessary to exam-
ine the statements made by different au-
thorities to at once find out how little
really is known, that the different au-
thorities do not agree, and in fact, to find
nothing but hopeless confusion. An-
other mysterious element is the factor of
safety ; for suppose it is known exactly
to what amount each member of a struc-
ture is strained with certain loads, what
is to determine the strain per square inch

which the material should bear with a
maximum load ?

This is simply a matter of opinion, and
cannot be fixed definitely either one way
or another ; but taking the practice of
different engineers, a variation of opinion
is found to the extent of at least 25 per
cent., which' would, of course, materially
affect the weight of girders. Again, this
factor of safety would have to vary in
the same structure, for in some cases —
as, for instance, the lattice bars at the
center of a braced girder, or the abut-
ment ends of the top and bottom flanges
of parallel straight girders — the amount
of material really required is so small
that it could not be adopted practically,
and the section is increased accordingly ;
so it often happens that the amount of
material required under certain circum-
stances is determined not by abstruse
calculations, butjby the judgment of the
designer.

Taking all these things into considera-
tion, it seems very evident that a for-
mula containing all these uncertain ele-
ments cannot give anything but approxi-
mate results, and that being the case,
equally reliable and accurate results can
be obtained by using formulae which are
more concise and which thus reduce the
liability to error in the calculations. It
must not be thought, however, that the
author is advocating in any way a rule-of-
thumb method of designing girders — far
from it ; and he would mention as a type
of what he considers good and reliable
formulae, tables and diagrams— those
compiled by Mr. B. Baker — where every
detail as to the strains and weights of
girders can be determined sufficiently
accurate for practical purposes for most
types of girders, /rom the smallest to the
limiting spans.

The plate-web girder is considered by
many to be the simplest form of girder,
the calculations required for determining
the strains and subsequent distribution
of the metal being also supposed of the
simplest kind, and requiring very little
consideration. Thus we find that girders
of this class are often designed and con-
structed in a very reckless manner, very
little consideration being given to the
arrangement of plates, designs of joints,
and other so-called minor details — every-
thing being considered correct and safe
so long as there is " plenty of metal."

PLATK-WKB GIRDERS.

Instead, however, of the plate girder be-
ing of the simplest form, it is in reality
one of the most complex, and the consid-
eration of it involves one of the most
complicated problems which could pos-
sibly occur, and which cannot be so easily
determined as the strains in the different
members of a braced girder. The calcu-
lation of the strains in the flanges does
not offer any special difficulty, the
strains being easily determined by the
well known formulae ; but when the
strains in the web have to be calculated,
innumerable difficulties at once present
themselves. The web, of course, has
to be constructed to withstand the verti-
cal strains which are transmitted from
flange to flange, and which strain is
called the shearing strain. But the
question is, how are these strains trans-
mitted, and in what direction? This
point has been thoroughly investigated
by two of the first mathematicians of the
age — viz., Professor Airey and by Mons.
Bresse, the results of the investigation of
the former gentleman being communi-
cated to the members of the Royal So-
ciety in 1862.

There was, certainly, before this time
a correct general notion of the nature of
the strains in the web, but no actual
theory had been advanced by means of
which the strains could be mathemati-
cally expressed. From the experiments
made by Mr. Stephenson on the model
tube for Britannia Bridge and the mathe-
matical investigations of Professor Airey,
it was found that diagonal strains, both
compressive arid tensile, occurred in the
web, and that the angle of the diagonals
was about 45°. It was the consideration
of this that made Mr. Stephenson advo-
cate so strongly the adoption of web
plates in preference to lattices, and he
argued that it was only necessary to con-
ceive a lattice girder, with the lattice
bars close to one another, to have at once
a web plate girder with two webs, one
web acting in compression and the other
in tension ; and as there is nothing to
prove that a bar in tension in direction
of its length may not at the same time
resist a compressive strain in direction of
its width, it follows that- only one-half
the section of the web would be neces-
sary if the metal were in one piece in-
stead of being divided. This view was
also supported by Professor Airey, who

commenced his investigations by proving
the theorem that " whatever be the num-
ber and direction of the forces of com-
pression and tension, their combinations
may in all cases be represented by the
the combinations of two forces at right
angles, these forces being sometimes
both of compression and sometimes both
of tension, and generally unequal in mag-
nitude." He then investigated the con-
dition of two such forces acting at each
point of the web, paying particular atten-
tion to the condition at the ends of the
girder resting on the pier. In all verti-
cal sections of the web he found both a
tensile and compressive force resisted by
similar forces of equal amount acting in
reverse directions ; but at the ends of
the girders these opposing forces did not
exist, the vertical pressure which a hori-
zontal portion of the web had to resist
at the base being equal to one-half the
distributed load and reduced uniformly
to the top of the girder.

Having shown the nature of the
stresses in the web, it remains to be
shown how the strength of a web plate
is to be calculated in designing a girder ;
and here difficulties and wide differences
of opinion at once present themselves.
It is astonishing how little this question
appears to have been taken into consid-
eration even by persons who are con-
stantly designing girders ; and the ma-
jority of persons, when asked by what
rule they determine the thickness of the
web, have not been able to give a satis-
factory reply ; and most of them have
admitted that they never calculate it, but
make it what they think is sufficient.
This accounts, no doubt, for the number
of curious plate girders which may «be
occasionally seen on their way to the site
of some large building in course of erec-
tion, or even sometimes to a railway in
course of construction.

Taking it for granted that the stresses
in the web do act in a diagonal direction,
at an angle of 45°, it will be as well to
see how different authorities then treat
the question of determining the neces-
sary thickness.

Professor Reilly, of Cooper's Hill
College treats it as follows : " Let N be
a very small cubical element in the web.
The diagonal of the square in the line
AB is the direction of a normal com-
pressive stress of equal intensity to the

VAN NOSTRAND'S .ENGINEERING MAGAZINE.

shearing stress, acting in all sections of
the small cube which are normal to that
diagonal ; the other diagonal being the
direction of a similar tensile strain.
Consider a narrow diagonal strip of the
thin web plate, whose mean fiber is the
diagonal of the square produced both
ways to meet the top and bottom angle
irons of the girder, and whose lengths/.
The web may be conceived as made up
of a number of such strips, and further,
they may be considerd as isolated — a
supposition which is much on the side of
safety, as each strip will be in the condi-
tion of a long diagonal pillar or stout en-
castre at each end, by being gripped be-
tween the angle irons ; the least breadth
of the pillar being the thickness of the
web. Then determine the intensity of
the resistance to failure by lateral bend-
ing or buckling of such a diagonal pillar,
and compare it with the intensity of the
shearing stress on a vertical section on
which the shearing force is greatest,
which is close to the end of the span —

Let po— force required to buckle the
pillar.

qo= shearing stress on a vertical
section.

Then— must give a sufficient factor of
go

safety,

which may be fixed as low as 2, consid-
ering that the diagonal strips which have
been treated as isolated strips are really
connected with one another, so as to
form a continuous web, and by their
mutual support oppose a greater resist-
ance to buckling than is given by the cal-
culation for po; how much greater there
is at present no known method of com-
puting." The following is an example
of a cross girder worked out :

Let the distance between the rivets of
the angle irons be 2I-in., then the length
of the pillar taken in the angle of 45°
will be

21^2= say 30-in.

36000

po = l

r =

36000
~900~

36000

3000*

30009 64 3.13

= 5.14 tons per square inch of the sec-
tion of the plate.

Let the shearing force at a section
near the end of span =22 tons,

the qo =

shearing force

sectional area of web § + 28

=2.1 tons per square inch,

then the ratio— =-^ =2.45, which Pro-
qo 2S.1

fessor Reilly considers is more than suf-
ficient for a factor of safety.

Professor Kankine treats the matter
in a somewhat similar manner, but has
entirely different notions as to the factor
of safety to be employed. In his " Man-
ual of Civil Engineering," page 529, he
says:

" The thickness of the web is seldom
made less than f -in., and, except in the
1 largest beams, is in general more than
sufficient to resist the shearing stress.
! In those beams in which it becomes ne-
i cessary to attend specially to the power
of the vertical web to resist the shearing
action of the load, the amount of that
shearing action is to be computed by the
! formulae of Art. 161, &c. It is, then, to
! be considered that the shearing stress at
the neutral axis is equivalent to a pull
and a thrust of equal intensity, inclined
opposite ways at 45°, and that the ver-
; tical web tends to give way by buck-
'■ ling under the thrust, so that its ulti-
mate resistance in pounds per square
inch is given by the following expres-

sion

Let £= thickness of plate = say _
then by the well-known Gordon's form-
ula for columns, deduced from the ex
periments of IJodgkinson, the resistance
of the pillar to lateral flexure is

po=l

36000

3000J2

t being the thickness of the plate and
5 the distance measured along a line in-
clined at 45° to the horizon, between two
of its vertical stiffening ribs, or if it has
no such ribs, between the upper and
lower horizontal ribs. The intensity of
the shearing action of the working load
should not exceed one-sixth of the resist-
ance given by the above formula."

PLATE-WEB GIRDERS.

That is to say, taking the same sym-
bols as Professor Reilly,

— must not be less than 6.
go

Mr. Bindon Stoney, in his book on
" Strains in Girders," in speaking of the
vertical strains in a web, remarks as fol-
lows :

" This vertical strain has been aptly
named the shearing strain ; but few
writers until the last few years have no-
ticed the practical results which follow
from the fact that this force can be com-
municated from section to section only
through the medium of some diagonal
strain. Respecting the exact directions
of the strains wrhich this shearing force
develops to a continuous web, we know7
nothing positively ; it is probable that
they assume various directions, crossing
each other like lattice work — some verti-
cal, some diagonal, and perhaps some
curved. However this may be, we know
that certain of them must be diagonal,
since the weight which is a vertical force
produces strains in the flanges which are
longitudinal, through the medium of the
web, which, in fact, fulfills the part of
bracing in a lattice girder." Further on,
in speaking of long plates, he says : " An
isolated plate under compression may be
regarded as a wide rectangular pillar, or
as a number of square pillars placed side
by side, and it will therefore follow the
laws of pillars, so far as deflection at
right angles to its plane is concerned.
If, however, the plates form the sides of
a tube (as in the web of a girder), this
rule does not apply, since in that case
they yield by buckling or wrinkling of a
short length, and not by flexure ; being
held in the line of thrust by the adjacent
sides, which enables them . to bear a
greater unit strain than if not so sup-
ported along their edges." Further on,
when speaking of how the thickness of
the web is to be determined, he says :
" When calculating the area of a plate
web from the total shearing strain, it is
a safe rule to adopt four tons per sec-
tional area of web as the maximum shear-
ing strain ; but this rule gives no idea of
the amount of material requisite for stif-
fening the web, and which can only be
determined by experience in each sepa-
rate case."

Mr. B. Baker contributed a very inter-

esting paper to the Institution in 1880
on the " Practical Strength of Beams,"
from which a few extracts will be made,
as bearing upon the present subject.

After experimenting on a large num-
ber of girders, details of which may be
found in his paper, he says : " The
strength of a plate web, according to
Professor Airey, Mons. Bresse, and near-
ly every other mathematician, is gov-
erned by the resistance of the web to the
diagonal compression due to the shear-
ing stress. This may be practically true
in some cases, but it was not so in that
of the 24in. by J web of girder g, or the
shearing strain sustained would have
been double the 4^ tons per square
inch, which crippled the web ; neither
was it approximately true in the instance
of some girders with 36 by J webs which
the author tested, with the view of deter-
mining the real nature of the stresses in
a plate girder as generally constructed."
He then describes the girders, and the
result of the experiments, and says :
" The maximum shearing strain was 45
tons, or at the rate of 4.3 tons per square
inch of the gross section of the web. The
resistance of the thin web to diagonal
compression would be less than a third
of this, so that the strength was obvi-
ously not governed by the conditions
laid down in ordinary theory. The per-
manent set of l-16th of an inch could not
be due to excessive compressive strains
on the web, because the total deflection
of the girder was far too small to per-
manently bend such a long elastic col-
umn as that constituted by the \ web.
It could only be due, therefore, to the
stretching of the web under tensile
strains. From a careful consideration
of the phenomena exhibited, the author
was led to the conclusion that at a point
in the center of the web plate experi-
mented upon, when by the ordinary
theory the diagonal strains would be
about 4J- tons per square inch, both in
tension and compression, the strains
were, as a matter of fact, 11 or 12 tons
in tension, and half a ton or a ton in
compression." Mr. Baker verified his
experiments on the preceding girder by
numerous others on five girders of equal
size, but with varying proportions of
flange and web, and obtained practically
the same results. He also made models
of the girders to scale with wooden

VAN NOSTKAND'S ENGINEERING MAGAZINE.

flanges and stiffeners, and paper webs,
and tested them to destruction, when he
found the phenomena observed in the
full- sized girders were repeated to exag-
geration in the models, the lines of stress
being shown with conspicuous clearness.

The latter experiments proved more
suggestive than all the experiments on
the iron girders, and all the mathemati-
cal investigations on the subject; and
'Mr. Baker says that "after witnessing
them there was no difficulty in forming a
clear conception of the nature and inten-
sity of the strains occurring in a plate
web as ordinarily constructed," and fur-
ther states that " the local weakness in
the preceding girders, which would have
determined failure before the full
strength of the flanges had been devel-
oped, was again thinness of web. In the
three cases cited, the strengthening of
the locally weak portions would be a
subject rather for practical experience
than of theoretical investigation."

He then states : " So far as web plates
of medium size are concerned, he is of
opinion that the general condition laid
down by Mr. (Jhanute, in his specifica-
tion for the Erie Railway bridges, meets
all the requirements indicated by experi-
ment. These are: that the shearing
strain shall not exceed half that allowed
in tension on the bottom flanges of a
riveted girder, and that when the least
thickness of web is less than l-80th of
the depth of the girder, the web shall be
stiffened at intervals not over twice the
depth of the girder." Mr. Baker then
concludes by saying : " Hundreds of ex-
periments might be cited to show that
the practical strength of a beam, at low
strains as well as at high strains, is de-
pendent, to an important extent, upon
other considerations than those included
in the mathematical investigation. In
other words, it is certain that the less
strained fibers in a beam ' practically '
help their more severely strained neigh-
bors at low strains, as well as at high
strains, although 'theoretically," as M.
Barre and St. Venant and others have
shown, the assistance would appear to
take effect at high strains only."

Having briefly stated the opinions of
different authorities, it now remains to
sum up the various theories which have
been advanced, and, if possible, to de-
duct some practical result. It will have

been seen, however, that the opinions
expressed are so widely different, that to
attempt to reconcile one with another
would be utterly impossible ; and it is
only necessary to work out an example
by different methods to at once see the
amazing discrepancies in the results.
For instance, if the calculations for a
bridge, say of 100ft. span, having two
outside girders, carrying a double line of
rails, be worked out, it will be found
that the thickness of the web plate at the
ends will vary, according to the different
formula adopted, from about J-in. to
1^-in. thick. The method adopted by
Professor Rankine, Professor Reilly and
others, it has been stated, is to treat the
web plate as so many isolated pillars,
fixed at the end. Now, the question is,
Is that a legitimate way of treating the
question? The author is strongly of
opinion that it is not. In the first place,
the conditions are certainly not those of
a loaded isolated pillar, for, as Mr.
Stoney remarks, they certainly receive
support from one another, and from the
top and bottom angle irons and stiffen-
ers ; again they are crossed at right an-
gles by strips of metal in tension, which
must also strengthen them, and the
length of the pillars gradually diminishes
at the top and bottom of the web as they
appoach the junction of the vertical stif-
feners and the top and bottom angle
irons, and, being shorter, are stiffer, and
so add lateral strength to each ideal

po
pillar. If the factor of safety — as given

by B-ankine be adopted, the thickness of
web will be out of all proportion, being
far too thick ; but Professor Reilly takes
the above conditions into consideration,
and admitting that there is no known
method of computing the exact resist-
ance to buckling, gets over the difficulty
by adopting a very low factor of safety,
thus obtaining reasonable results. But
if the formula for columns has to be so
cut and carved to make it give satisfac-
tory results, why use the formula at all ?
Equally satisfactory results could be ob-
tained by using any other formula, say,
for instance, the one for obtaining the
bursting pressure of a boiler ; by making
the shearing stress equal to the boiler
pressure, and the length of the column
equal to the diameter of the boiler, the

ON THE DETERMINATION OF THE QUALITY OF IRON AND STEEL. 55

thickness of the web could be obtained
by working out the usual formula for
bursting pressure, and then dividing by
some wonderful constant to make it lit.

The fact of having to use such a doubt-
ful factor of safety, and the experiments
made by Mr. Baker, prove conclusively
that the web cannot rationally be con-
ceived as a number of isolated columns,
and therefore to treat it as such appears,
on the face of it, most unreasonable and
decidedly incorrect. The author's prac-
tice has been to allow a shearing stress
of 2J tons per square inch on the gross
vertical sectional area of the web for
large girders, and 3 tons per square inch

for small shallow girders ; the spacing of
the vertical stiffeners being determined,
not by theory, but from the results of
practice. This method has been con-
demned by some engineers as being a
rule-of-thumb method ; but when it is
supported by such an authority as Mr.
Baker, who has proved by experiments
and by reasoning that the " practical
strength " of beams is different from that
dictated by theory, the author feels per-
fectly justified in adopting and advoca-
ting a rule which is founded on actual ex-
perience, and which gives far more relia-
ble results than those obtained by doubt-
ful theories.

ON THE DETERMINATION OF THE QUALITY OP

IRON AND STEEL.

By PROF. LUD. TETMAJER.
Translated from "Eisenbahn," Zurich, for Abstracts of the Institution of Civil Engineers.

In a previous article on the same sub-
ject the author gave his reasons for ob-
jecting to the method of determining the
quality of iron and steel as recommended
by the Commission of the German Rail-
way Union ; namely, by means of the
breaking strains and the contraction, and
substituted for it the working capacity,
i. e., the product of tensile breaking
strain into the elongation.

where rj is constant for a certain kind of
metal. Further experiments by the au-
thor have confirmed the constancy of 77,
and have shown that even for different
brands of the same kind its variations
are of no practical importance ; the dif-
ferent brands at present in the market
can therefore be treated together in
groups on the basis of the working
capacity.

In the above equation a determines
the class of quality of a kind or group,
r) the kind of the material. Consequently,

minim, a .

is constant for a certain class,

and this constant

c=j3X

is the coefficient determining a class, /3
being given in ton per square centimeter,

and A in percentage of a given length of
bar. The law of dependence of ft from A
is expressed by a hyperbola, whose
asymptotes are the axes of the system,
and the different classes of quality can
be distinguished from each other by
pieces of hyperbolas.

Availing himself of the results arrived
at by prominent experimentalists, and
having regard to the interests of both
railway companies and iron masters, the
author has worked out the following
classification :

A. Puddled iron (four classes).

I. quality, c=68 ton per cent.
II. " c=48 " "

III. " c=34 "

IV. " c=24 " "

B. Cast malleable iron or steel (one

class).

c=93 ton per cent.

[For example, iron of a breaking
strain=3,200 kilograms per square centi-
meter, and an elongation of 12 per cent.,
has a c=38.4, and would accordingly
rank in class III. — Ed.]

The limiting figures for the various
classes would have to be agreed upon
from time to time, although it is not

/)6

VAN NOSTRAND S ENGINEEEING MAGAZINE.

likely that those of group A. will be
greatly modified. The results of experi-
ments with this material, when plotted
on a system of co-ordinates ft and A, are
spread very evenly over the range of the
above four coDstants ; the results from
material of the group B„ on the other
hand, lie much closer together when
plotted on the system, and a hyperbola
c=93 can be drawn easily; in such a
way that the great bulk of the plottings
]ies above, and not very far above it.

Graphical interpretations of the same
experiments on the basis of breaking
strength and contraction did not bring
to light any rule, while the grouping of
the plottings according to fi and A seems
to confirm the correctness of the author's
method. The curve c=9S is, in the
opinion of the author, still too low ; but
it is higher than the lines proposed by
the German iron masters, which are so
low that, according to them, a consumer
would be obliged to accept almost any-
thing that is produced.

The conditions of specifications with
reference to quality of metal would have
to be stated in the following forms
(given as an extract) :

Prime rivet and bolt iron.
Min. tensile strength /?=3.8 ton per sq.

centimeter.
Coefficient of quality c=68 ton per cent.

Round bar iron for machinery and
bridges.
Min. tensile strength /i— 3.6 ton per sq.

centimeter.
Coefficient of quality c= 48 ton percent.
Cast- steel rails.

/?=from 5.2 to 6.4.
c=93.
Cast- steel tires.

/i=from 4.6 to 5.5.
c=93.

Cast malleable iron boiler plates.

/3=irom 3.7 to 4.8.
c=93.
&c.

CURVES AJTO CROSSINGS FOE RAILWAYS.

By S. W. ROBINSON, C. E., Prof. Mech. Eng., Ohio State University, Columbus, Ohio ; Member of the
Board for Inspectors under the Hon. H. SABINE, Commissioner of Railroads for Ohio.

I. FORMULAS AND TABLES FOR EASEMENT
CURVES AS ADAPTED TO FIELD PRACTICE.

Since the article on Railway Econ-
omics * was written the problem of the
" easement " curve has been pursued
farther with a view to putting results
and facts in the most convenient shape
possible for use by field engineers.

It might at fiist be imagined that the
complexity of practice with any easement
curve must necessarily be so great as to
render its use entirely out of the ques-
tion. But a little consideration of the
table of quantities given below will show
that this is not the case ; indeed, from the
fact that the quantities needed are al-
ready made out and given in tabular
form, it may be found easier to construct
easement curves than circular curves.
Though a great variety of easement
curves is possible, only one is necessary,
and when this one is selected, all the

* May Magazine.

quantities pertaining to it which are
needed in practice can be at once com-
puted and tabulated, the table being ex-
tended to include any case of practice.
This is seen to be possible from the fact
that any proper easement curve must be
a sort of a spiral, beginning with an in-
finite radius at the point of departure
from the straight tangent, and extending
to where the radius of curvature be-
comes equal to that of the principal
circular curve to be joined with it.
Hence the table should be carried to the
smallest admissible radius of principal
circular curve; which table representing
some one carefully-selected spiral or
easement curve, is ready for every case,
and furnishes deflection angles already
made out for part of every curve to be
run in practice. Indeed it is possible by
aid of the table to run in. a complete rail-
way curve between any two tangents,
consisting wholly of two portions of the
easement curve in common tangency,

CURVES AND CROSSINGS FOR RAILWAYS.

and without computing a deflection
angle, nor summing them for total de-
flections.

On the other hand it is well known
that some species of easement curve is
absolutely necessary for the transfer from
a tangent to a circle curve without the
disturbance of the lateral equilibrium.
Hence easement curves are a necessity to
perfect track.

A number of curves have been pro-
posed for effecting this easing, and a few
of them have been used in practice. But
probably no rules for practice heretofore
published came nearer to realizing the
needs of practice than those presented
in a most excellent article in the Mail-
road Gazette of Dec. 3, '80, by Ellis Hol-
brook, C.E., of Richmond, Ind. A table
is there given which contains most of the
quantities required. Mr. Holbrook is
introducing these curves on the Pan
Handle Hailroad.

The methods of that article are found
of such rare merit that they are followed
largely in this, the chief difference being
in additions which aim to more fully
anticipate the needs of practice. A dif-
ferent curve is, however, adopted in the
present instance for reasons soon to be
given.

The curve of Mr. Holbrook is a spiral
with infinite radius at the tangent point,
and with the radius of curvature varying
inversely as the distance from the tan-
gent point as measured along the track.

From the general considerations of-
fered in the principal article above, under
" The Track Line," it appears that the
spiral there adopted is one in which the
radius of curvature varies inversely as
the square of the distance from the point
of tangency. The object in choosing the
square was to reduce disturbances, due
to entering upon the curve, to the least
possible value, as fully discussed in the
principal article. For the same reason
the law of the square is still retained.

The elevation of outer rail on curves
is well known to be inversely as the
radius of curvature of the track curve.
Hence in the present case the elevation va-
ries directly as the square of the distance
from the point of tangency. By choos-
ing the law of the square, the accelera-
tion of the car in its rotation on a longi-
tudinal axis as already explained is made
constant, and to a person sitting at the

\ extreme side of a car, the only sensation
due to entering upon a curve would be
that of a slight increase of weight, or of
decrease, as the case might b«* and
j which would continue constant tL ugh-
out the easement curve. But where the
variation of elevation and of consequent
! rotation of car on a longitudinal axis is
i as the first power of the distance from
the tangent point of the curve, the eleva-
; tion of a person at the extreme outside
j of the car would be uniform as the car
! rotates, but that uniform rate would have
a sudden beginning at the initial point
of the curve ; the action being like that
of imparting a uniform motion upward
to a body from a state of rest by an in-
stantaneous knock. Though the prac-
tical effect of this instantaneous impulse
may be declared insignificant ; yet from
a scientific standpoint it is incorrect, and
the law of constant acceleration is more
acceptable.

! RULES FOR RUNNING THE EASEMENT CURVE.

Let Fig. 1 represent a simple case

j where two tangents intersect at C. Take

! D and H as tangent points, from which

a circle curve shown by dotted lines

might be put in from a center O.

Let A and B be the tangent points for
the new curve in which A.G and BJ are
I the equal easement curves, and GJ the
principal, or intermediate circle curve.
Perpendiculars at A and B meet in O,, at
an angle equal the angle of intersection
of the tangents. The circle may be ex-

VAN NOSTRAND'S ENGINEERING MAGAZINE.

tended back from G to F where its tan-
gent is parallel to AC. O is taken a com-
mon center to the dotted circle DH, and
the principal circle GJ.

In running the curve in the field, we
may start at the point A. With chords
and tabulated deflection angles, run to
G ; then set the instrument at G and fun
the circle GJ ; then go to B and run the
easement curve BJ. To eliminate in-
accuracies it may be advisable to run the
two easement curves first. Then with
the instrument at G examine the total
deflection angle for J. If the discrep-
ancy is small, set on J to dispose of it,
and connect G and J.

To conveniently express relations be-
tween quantities, take

I=the intersection angle at C,=

DOH^AC^B. Then DOC^I.

R=the radius OD to the ordinary

circle curve dotted in,
R,=the radius OG, OE, OJ to the
principal curve.
H— Rj=DF=the normal distance be-
tween the circle curves named.
T=the tangent DC to the circle to

radius fi.
T1 =the tangent AC to the new curve.
T\ --T= AD = difference of the two tan-
gents.
*j=the angle between the tangent
line to the easement curve at G,
and the tangent T. ^=GOF.
DA = total deflection angles laid off
at A, from the tangent AC for
running the easement curve.
The greatest one for a particu-
lar curve is GAC.
D/ = total deflection angles at same
point on the easement curve,
from a line parallel to AC, to
points beyond.
D* _2oo= total deflection angles for the
instrument at 200 feet from A
as. measured along the ease-
ment curve.
J=length of the easement curve
counting from A.
SB, and yt = co-ordinates to the point G,
as shown, but given for every 10
feet of the curve /.

From the fact that the easement curve
AG is a certain definite spiral curve of
increasing curvature, it is evident that it
will fit all circle curves, GJ, of whatever
radius; because, beginning with an in-

finite radius, it is only necessary to run
it to where its radius equals that of the
principal curve GJ, whatever that may
be. Hence the various quantities per-
taining to the easement may be calcu-
lated once for all for every point and
tabulated. To do this we require equa-
tions, such for instance as are given be-
low.

According to considerations already
presented, we have

const

where h is the difference of elevation of
the two rails, and p the radius of curva-
ture of the spiral at any point. Also,

h = const, f = const, ri* = const . F =

const

Take the constants such that
h=al"

and

Then

ph —

Ml2

These are the fundamental relations.

Now at any point on the spiral ease-
ment curve the radius of curvature p is
perpendicular to a tangent drawn to the
same point of the curve ; the latter, as
above explained, making the angle i with
the principal tangent T. Hence for a
small variation of the position of the^
point considered, along the curve I by an
infinitessimal dl, the radius p will swing
through an infinitessimal angle di.
Hence we have the relation

pdi=dl,

or by introducing the value of p

di=m2dl

■

Integrating this for limits reckoned
from zero, we have

i=M3
Also by the figure it is easily seen that

-V-.=cos ^=cos ol%
dl

dx . .

— =sin i=sm or
dl

CURVES AND CROSSINGS FOR RAILWAYS.

Expanding the sine and cosine into
series, we have

dy=1 (biy (biy

TSlA ' &c"

dx (bry (biy

dl 1.2.3 1.2.3.4.5

&c,

which, for limits reckoned from zero be-
come

M»-

(biy (biy

*=biil-u

2.7 ' 1.2.3.4.13

(biy , (^s)

2.3.10 ' 1.2.3.4.5.16

-&c.)

From these equations, the co-ordi-
nates to the spiral curve can be com-
puted.

If we apply the subscript 1, to a par-
ticular set of quantities belonging to the
point G in the figure, we may write

Rl=PlZ=3^7;
B — Rj^JCj— K^l— cos ij,
1— cos f

■X.

Sbl

2 >

«-^-'§^)'

TI-T=y1-R1 sine,

sin i.

Vx 3bi;

18 V 20 +873i /

K l(biy

For total deflection angles at A we have
tan Da =-

when x and y are co-ordinates to the
point to be located by the angle D& .

For deflection angles laid off at any
point x' y' on the curve, from a line par-
allel to the tangent T, we have

tan Di =

x — x

y-y'

which applies for points forward or back
x' y' . This deflection angle is useful
when it is desirable to move the transit
instrument from A to a point on the
curve for passing obstacles, &c.

From a point on /, 200 feet from A,
measured along the curve,

D/=

200

x— a*20o

//- 2/200

A deflection angle from the tangent T
at any point ?/, on that tangent for lo-
cating points xy on the curve, is given

tanDT =

y-y

These deflection angles are intended
for use in the ordinary way in practice,
along with the chain for running the
curve.

The tangent T to the dotted curve is
given in terms of the radius R of that
curve, and the intersection angle I, by
the well known relation

T=Rtan£I.

CONSTANT FOR PRACTICE.

For the elevation of the outer rail we
have for 30 miles per hour of train speed,
and for I in feet,

A=af = .0000793f inches,
= .0000066£2 feet.

For 45 miles per hour, and I in feet.
A=a72=.0001785/2 inches,
= .0000149f feet.

The value of 6 which has been adopted
is given by

com. log 6=1.8955-10.

SPECIAL CASE OF EASEMENT CURVES ONLY.

That the whole curve may consist only
of two equal portions of the easement
curve tangent to each other in the mid-
dle, the points G and J must fall at E,
and we must have

also radius at E= radius for !&=.£I or

I_ L 1L
Sbl'2 "37~~36I

R . = ■

where i or I is expressed in arc to radius
unity, and common log 6 = 1.8955— 10.

The length of the entire curve is twice
the length lx to the point where »/=i I.

PATH OF CENTER OF OAR.

It has been explained that the center
of gravity of the car is the point which

VAN NOSTEAND'S ENGINEERING MAGAZINE.

should describe the curve here laid
down, and not the center point between
the wheels. This requires that the track
at the curve shall be laid outward of the
line run by the instrument and chain, by
an amount about equal at any point to
the elevatioD of the outer rail ; since the
center of gravity of car and load is above
the rails a distance about equal to the
track guage.

THE FIELD PRACTICE.

To facilitate the field operations in
running easement curves, values have
been computed for every 10 feet of the
curve and tabulated so that the curve
may be staked out directly by stakes set
10 feet apart or at multiples of 10 feet.
These computed quantities are given in
the accompanying table, which the en-

Table for facilitating the Field Work of Easement Curves.

Rx.

Da.

8
ii

*i»

4i '-
^8

*1-

V\>

o o

1
P5

ft£

£%

424100

0° 0'

424100

0° O'oO"

6.67

0° 0' 0"

0°00' 1.6"

.001

.00

106025

3 20

13.3

< • * •

13."

.003

.01

47124

7 25

20.0

07'

44.

.001

26506

0°13

26506

0°13'16"

26.7

1'44

.011

.03

.005

16964

20 22

33.3

3 23

.012

11781

0 30

11781

29 18

40.0

1'26

5 50

.023

.05

.025

8656

.01

8656

39 45

46.7

2 18

9 18

.047

6626

0 52

6626

52 00

53.3

3 26

13 50

.042

.10

.080

5236

.05

5236

1 05 40

60.0

4 51

19 43

.127

4241

1 19

.07

4241

1 21 06

66.7

6 44

27 02

.065

.15

.196

100.

3504

.10

3504

1 38 09

73.3

9 03

35 58

.289

110

2945

1 53

.14

2945

1 56 46

80.0'

1141

46 4.3

.096

.21

.408

120

2508.

.19

2508

2-17 02

86.7

14 49

59 24

.560

130

2164.

2 39

.25

2164

2 38 56

93.3

18 23

1°1410

.131

.29

.755

140

1884

.33

1884

3 02 30

100.0

22 56

1 31 14

1.000

150

1657

3 28

.43

1657

3 27 30

106.7

27 41

1 50 42

.172

.39

1.288

160

1468

.52

1468

3 54 22

113.3

32 58

2 12 54

1.630

170

1310.

4 22

.68

1309

4 22 30

120.0

39 25

2 37 42

.213

.48

2.064

180

1177

.84

1176

4 52 30

126 7

46 18

3 05 22

2.560

190.

1061

5 24

1.04

1060

5 24 23

133.3

54 02

3 36 18

.264

.59

3.144

199.9

963

1.26

962

5 27 42

140.0

1°02 34

3° 52 02"

4 10 18

3.820

209.8

878.

6 32

1.53

876

6 32 30

146.6

1 1155

4 10 25

4 47 48

.321

.72

4.603

219.9

803.

1.82

801

7 09 28

153.3

1 22 34

4 29 25

5 28 48

5.500

229.8

738.

7 46

2.17

736

7 47 28

160.1

1 33 24

4 49 48

6 13 36

.385

.86

6.515

239.8

681

2.56

678

8 27 30

166.8

1 45 32

5 1130

7 02 12

7.670

249.8

680

9 06

3.00

627

9 08 50

173.5

1 58 45

5 34 10

7 55 12

.451

1.01

8.974

259.7

585.

3.48

582

9 5126

180.2

2 13 07

5 58 05

8 52 12

10.44

269.7

545

10 31

4.02

541 10 36 21

186.9

2 28 12

6 23 05

9 53 30

.523

1.18

12.06

279.6

509

4.63

504 11 23 17

193.5

2 44 22

6 50 25

10 59 18

13.84

289.3

476

12 02

5.30

471 12 11 14

200.1

3 02 19

7 19 10

12 09 42

.595

1.34

15.87

299.0

447

6.05

441 13 01 00

206.8

3 2115

7 44 30

13 25 24

18.09

308.7

421

13 40

6.87

414 13 52 30

213.5

3 4107

8 21 00

14 45 24

.676

1.52

20.51

318.5

397

7.75

389 14 46 08

220.2

4 02 30

8 54 00

16 11 12

23.18

328.1

376

15 15

8.71

867 15 40 30

226.9

4 25 20

9 28 00

17 43 00

.762

1.71

26.11

337.7

356.

9.87

346 16 37 04

233 6

4 49 10

10 03 30

19 19 00

29.27

347.1

338

17 00

11.00

327 17 35 05

240.4

5 14 23

10 41 22

21 01 00

.851

1.93

32.70

356.5

321

13.20

309 18 44 30

247 1

5 40 55

11 20 30

22 49 00

36.38

365.7

308.

18 41

13.45

294 19 35 00

253.8

6 08 34

12 00 30

24 43 00

.952

2.14

40.35

374.9

294

14.93

279 20 38 51

260.6

6 36 00

12 37 50 '

26 44 00

44.40

383.8

282

20 12

16.66

265

21 45 05

267.4

7 04 00

16 1

28 49 46

1.057

2.38

48.62

392.8

Note.— Difference between a 100 feet chord and its arc at 400 feet from A or for the lower line of table is 0.-^86 fe#t
and it varies as the square of the degree of curve, and cube of the chord length.
The angle to the principal circle curve=I— 2it.
The value of 1-2 it can never be negative in practice. It equals zero when G and J fall at E in the figure.

CURVES AND CROSSINGS FOR RAILWAYS.

gineer should have placed in his note
book for convenient use in the field.
To illustrate the use of the table take ,

the following

EXAMPLE.

Given the intersection angle 1=60°
and the radius, R, for an ordinary circu-
lar curve = 1061 feet.

Then by the usual formula and calcu-
lation for circular curves,
'J = R tan £ 1=1061. tan 30°=612.6 ft.

Hence to run in a circular curve, we
go 612.6 feet back on the tangent from
the intersection point, and start with de-
flections and chaining, the total deflec-
tion having been made out.

But to introduce the easement curves
we must go back from the intersection
point the 612.6 feet, plus the tabular dis- 1
tance, T — T=133.3 found opposite R= |
1061. or 612.6 + 133.3 = 745.9 feet=T, ;
and from this point — A, in the figure —
start with the chain and the total de-
flection angles given in the table ac-
cording to the chord length. For 10
feet chords, setting stakes 10 feet apart,
use all the deflection. Da, given in
the table. For 20 feet chords use al-
ternate ones. For 50 feet chords use
the 49", 6' 44", 22' 56" and 54' 02".
For any length of chord we must in this
example end the easement curve at 200

feet, because by the table —=20, or 1=
J 10

200 where R=1061; and hence the last

total deflection on the easement curve

will beDA=54' 02".

At this point the radius of the ease-
ment curve is Rt = 1060 feet ; and this is
the radius of the principal, or circular
curve extending it. The angle between
the tangent to the easement curve at this
point and the tangent T is ^ = 3° 36' 18",
as given by the table. Hence the instru-
ment can readily be set up at the end of
the easement curve and brought to
tangency. The circle may then be run,
its deflection angle being half the degree
of the curve or 2° 42' 12" as obtained
from the table.

The length of the easement curve I, is
200 feet.

The angle of the principal curve will
be I_2;i=60°-7° 12' 36" = 52° 47' 24".
This divided by the degree gives the
number of chords of 100 feet, and con-
sequently the length of curve.

If both easement curves have been run
before setting the instrument at G, the
work may be checked by sighting on J
with the total deflection for that point.

The elevation of the outer rail for
the principal curve is the same through-
out as for the easement curve at G, and
= .264 feet, = 3.1", for a 30-mile speed.
For points along the easement curve,
the elevation is given in the table.

These values of the elevation are the
amounts by which to set the track out-
ward in order to carry the center of
gravity of the car on the curve as al-
ready explained. Hence the principal
curve is to be laid outward about three
inches, all its length. The easement
curve is to be laid outward 0.2" at 50
feet; 0.8" at 100 feet; 1.8" at 150 feet,
and 3.1" at 200 feet, where the circle
curve begins. These are for the 30
mile speed, the offsets being found in
the elevation column of the table.

II. SPEED AT GRA.DE CROSSINGS.

The so-called "know-nothing stop"
appears to be in force everywhere at
points where one track crosses another
at grade. In some states this is obliga-
tory by state law. But the practice is
universal, and appears not to depend at
all upon state law.

Very little thought appears to have been
given to the subject of economical cross-
ings of railroads. In some instances as
much money appears to have been ex-
pended in cutting to make a crossing "at
grade " as would have been required to
fill sufficiently to put the crossing "above
grade." But in many instances thou-
sands of dollars more better have

! been expended to carry one line over
the other, than to have placed them at

\ grade.

Some roads will place their estimates

j of expenses for all their stoppages at a
single crossing point at from 100 to 500

! dollars per day. We will probably be en-

| tirely safe in basing figures on the lesser
amount, as true, for a great number of

j railroads. For 300 days to the year, the
$100 per day will pay interest at 6 per

i per cent, on an expenditure of half a mil-
lion of dollars. Hence at such a point

; as the one now considered, it would be
economy to make an expenditure of any-
thing less than $500,000, to carry one
line over the other. This money would

VAN NOSTRAND'S ENGINEERING MAGAZINE.

cut about a mile of tunnel. A hundred
such grade crossings in a state would
amount, on account of stoppages, to en-
ough to build, equip and maintain a first-
class railroad across the largest state
east of the Mississippi.

But more definite figures on this point
may be found of interest.

The forthcoming report of the Com-
missioner of Railroads of Ohio contains
the following figures, viz.:

Total number of grade crossings re-
ported by all roads in the State, 252.

Total miles of railroad, 5,835^-.

Average number of trains that passed
over each mile of railway during the
year, 5,680.

Gross earnings of all railroads in the
State for the year 1881, $33,116,271.

From these figures we find the aver-
age distance between two consecutive
crossings on any one line of road to be

- = 23.1 miles. Average number of

252

trains over each mile in one day ; count-
ing 330 days to the year, Sunday being
allowed as about a third of a day in

. 5,680 , „ AO _

tram running, is -^tt *= 17.03. Gross

earnings per day, ^^ =$100,352.

Assumiog the average distance run each
day by one train, at 14.3 miles per
hour, the time on the average required
for a train to move from one crossing
to the next, including all stops such as
for taking and discharging local freights,
taking water, stopping at crossings, &c,

23.1
is tt-^=1-61 hours ; or 96.6 minutes.
14.3

Now allowing five minutes as a fair
average for the time lost by a train in
making the crossing stop, we find that
5

, or 5.176 per cent, of the running

time is consumed in stopping at grade
crossings ; time which, except for the
crossing, would be used in making head-
way ; because steam is up and all the
needed men are at their posts of duty.
The 5 minutes is taken as an average
for all trains, freight and passenger ;
a figure which is placed considerably
higher by some good judges. By avoid-
ing this stop, it appears Ohio roads

could increase their daily earnings by

over 5 per cent of the actual earnings,

,, . ., I $100,352
or exactly to the amount =

$105,830 ; which shows a gain of $105,-
830 - $100,352 = $5,478 per day for
Ohio roads ; a gain in earnings which
it is fair to suppose would follow the
abolition of the know-nothing stop.

To find the cost of a single stop, we
have by multiplying the average number
of trains per day by the number of cross-
ings reported= 17.03 X 252=4292. = the
number of daily crossing stops. As these
cost $5,478, it appears that a single stop
costs as an average $1.28.

The total cost of stops for the year

1881 appears from the above figures to

be 330 X $5,478=1,807,740, or nearly two

millions of dollars. This capitalized at

6 per cent., amounts to the enormous

and seemingly incredible sum of over 30

millions of dollars. The actual number

of crossings is evidently only half the

number reported by all roads, because

any one crossing gets reported by both

of the roads intersecting. Hence the

number of grade crossing-points in Ohio

in 1881 is 126. It appears, therefore,

that there might be invested on 6 per

cent, borrowed capital at each crossing

. ... ,$30,124,000 «OQQ10n
point the sum of - — --^ = $239,120 ;

or nearly a quarter of a million of dol-
lars as the amount that might be ex-
pended at each crossing point for ap-
pliances which would enable trains to
pass the crossings at full speed.

In some States the law compelling the
know-nothing* stop has recently been,
repealed. This is true of Massachusetts
and Ohio, but the repeal only followed
convincing proofs that better systems
for making the crossing existed. Switch
and signal appliances have been so per-
fected of late as to place at the disposal
of Railroad companies means for parsing
grade crossings at full speed in a manner
conceded by those who are familiar with
it to be decidedly safer than by the old
compulsory stop.

To realize this fact of enhanced safety
it should perhaps first be noted that the
compulsory stop is not absolutely safe.
For instance a freight train on a down

* Called the know-nothing stop from the fact of the
passage of the law compelling it in Massachusetts the
year of the political " know-nothings."

CURVES AND CROSSINGS FOR RAILAVAYS.

grade approach, might become unman-
ageable and break into a train making
the crossing. A rear locomotive on a
long freight train, especially when around
a curve out of sight of crossing and flag-
man, might under certain circumstances
remain under steam without knowledge
of error, and push the forward end into
a crossing tram. Though such instances
are rare, yet they are known to have oc-
curred.

Suppose each branch of track at a
crossing to be provided with a derailing
switch, so that in each instance just
named above, the train in error would
have been derailed, or turned into a side
track. This would have avoided the
crash in the two instances mentioned, but
the four switches, while avoiding two
accidents, might occasion ten for the
extra attention they require ; unless ac-
companied by operating mechanism far
superior in control to that which has
been employed in past years. But the
modern greatly improved and wonder-
fully perfect interlocking switch and sig-
nal apparatus is fully competent to the
task.

Indeed the modern " block system," in
making a single block each way at the
crossing, would in all probability be as
safe for passing at speed when clear, as
would be the old-fashioned stop. But
the addition of the derailing, or side-
track switch on each branch of track,
and so worked by interlock, with the
signals of the block that only one track
can possibly be set clear at a time, seems
to leave nothing to be desired for abso-
lute safety ; at least for a far greater
measure of safety than is possible with
the old know-nothing stop.

Apparatus working with the degree of
precision and certainty just indicated is
already in use on some important lines
of railway, a notable instance being
found in the blocks by which the
Pennsylvania Railroad enters the city
from West Philadelphia to its magnifi-
cent new depot at Broad and Market
Streets. Here all the switches for hand-
ling the 250 trains per day which are
brought in and out of that depot, and
the signals for governing the movements
of those trains, are interlocked with each
other. In one tower is a machine with
56 levers, and by it are operated all the
switches and signals belonging to the

track, extending from the depot back to
a distance of about half a mile. By this
machine all the trains can be bandied at
anv one time by one man.

The most wonderful feature of all this
maze of tracks, switches, signals, and
operating rods, cranks and levers, is that
they are so interlocked with each other
that whenever the attendant (human and
fallible), by inadvertence, siezes the
wrong lever, he finds it locked. Thus
he cannot set the signals to clear for a
train to move until the switches are all
in correct position. The breakage of an
actuating rod leading to a signal would
leave the signal to the action of gravity,
and it is so made and weighted that it
would fall to the danger position, and
prevent the moving of the train until at-
tended to. Inaction, incapacity or sleep
of attendant simply causes delay. Signals
not being cleared, trains are stopped.

Such appliances instated at crossings,
would evidently provide safety next to
absolute ; and admit of the passing of
trains at nearly, if not quite full speed —
indeed at full speed when a rail- junction
reversible frog for closing up the rail
gaps shall come to be operated along
with the derailing switches. Then no
stops would be required at crossings ex-
cept as two trains, at comparatively long
intervals, would happen to require the
crossing at nearly the same time. Then
the signals and derailing switches would
stand against that one which was a mo-
ment behind the other in announcing its
arrival. It will then necessarily tarry
till the first has passed, when the releas-
ing of the " detector bar " will enable the
man in the tower to turn the signals and
switches just in use, back to the danger ;
thus unlocking the intersecting lines,
switches and signals, so that the second
train can be passed.

Rusty Bolts. — To remove bolts that
have rusted in without breaking them,
the most effectual remedy known is the
application of petroleum. "Care must
be taken that the petroleum shall reach
the rusted parts, and some time must
be allowed to give it a chance to pene-
trate beneath and soften the layer of
rust before the attempt to remove the
bolt. is made."

VAN NOSTBAND'S ENGINEERING MAGAZINE.

THE STORAGE OF ENERGY.*

From "Nature."

Thb subject of this lecture has been
called by the world at large, even by
well-informed Punch, " The Storage of
Force." Why, then, have I ventured,
in my title, to differ from so popular an
authority? For this simple reason —
that you cannot store force any more
than you can store time. There
is as much difference between force
and work as there is between a mile
and the speed of a train or between a
ship and a voyage. Work involves two
distinct ideas combined, whereas force
only involves one. When a weight rests
on the ground the weight pushes the
ground down with a certain force, and
the ground pushes the weight up with
the same force. If, then, there were
such a thing as a storage of force, the
mere resting of a weight on the ground
would be such a storage, since the force
exerted between the weight and the
ground never grows less. But, I need
hardly say, it would be beyond the
ability of the cleverest engineer to work
a machine, or drive a train, by using a
weight resting on the ground ; the very
expression, "dead weight," shows how
useless it is for the practical purposes of
producing motion. A weight resting on
the safety valve of a steam engine may
be a very good means of adjusting the
pressure at which the valve shall open
and liberate the excess steam, but this
weight will never work the engine.

Work is force exerted through space ;
if a weight P be raised through F feet,
PxF foot-pounds of work will be done,
and there will be a store of P X F foot-
pounds of work in the raised weight.

The continuous evaporation of the
water from the seas and rivers by the
heat of the sun, and its subsequent de-
posit in the form of rain on the hill tops,
supplies us with another very large raised
weight store of energy, and which is
practically utilized when the water fall-
ing down the hill side works out water
wheels and turbines.

Various stores of energy arise from the
separation of two bodies which desire to

* Abstract of a lecture delivered at the London In-
stitution, by Prof. W. E. Ayrton, F.R.S.

come together. The vast fields of coal
form an enormous store of energy, owing
to the tendency of carbon to combine
with oxygen. Copper which is found
pure, and zinc, when separated from the
oxygen with which it is combined in
nature, are examples of the same kind.
We may also have, a store of energy
arising from two bodies being too close
together, and which desire to move
apart ; as, for example, in a coiled spring,
in compressed gas, in two similar mag-
netic poles, or in two similarly electrified
bodies near together.

The experiments now shown are ex-
amples of energy previously stored being
utilized. This grindstone is being turned
by a falling weight, the ventilating fan
by falling water, this saw is worked by
the gas engine, the lathe by this galvanic
battery, and the sewing machine by three
Faure accumulators.

The water which is falling from the
top of the building, and which is work-
ing this turbine, was really stored in the
cistern for drinking and washing pur-
poses, and, although serving us as a
store of energy, it was not pumped up
for this purpose. Indeed the price
charged for water by the water com-
panies would prohibit its use for the pro-
duction of power. For with water at a
pressure of 100 feet, and at as low a
price as 6d. per 1,000 gallons, it would
cost Is. 4d. per horse power per hour if
the turbine had 80 per cent, efficiency.

In addition to the natural stores of
water energy on our hill tops, there are
also artificial stores of water energy, or
Armstrong's water accumulators, as they
are called, although invented long before
Sir William Armstrong's time, and which
are employed in many large steel works,
docks, &c. Water is periodically pumped
into a cylinder with a heavily- weighted
piston, which is therefore raised when the
water is pumped in. If then at any mo-
ment, at any part of the works power is
required, a tap is opened, and this large
weight falling at the reservoir cylinder,
drives out the water and performs the
desired piece of work.

Now I want to consider how far it

THE STORAGE OF ENERGY.

would be possible to drive a iramoar by
one or other of these various sources of
power. An ordinary tramcar for forty-
six passengers weighed 2£ tons, and
when full of people about 44 tons. To
pull such a car at the rate of six miles
an hour along an ordinary line requires
about 1£ horse power. To produce such
an amount of power for one hour re-
quires an expenditure of over 2,800,000
foot-pounds of work, or if produced by a
weight falling, say through 10 feet, would
require the weight to be over 100 tons.

Armstrong's water accumulators are
therefore clearly useless for the purpose,
and coiled springs are too cumbersome.

Steam engines are occasionally em-
ployed on tram lines, and from the point
of economy are much superior to horses ;
but there is the great disadvantage of
the smoke, noise, and the terror of the
horses of other vehicles. A detached
tramway engine weighs as much as a
full car, consequently nearly half the
total horse power employed is used in
propelling the engine and boiler, and
there is also the waste of power caused
by the rapid radiation of heat from the
boiler of a small engine. Gas engines,
though saving the weight of the boiler
and coal, have the compensating dis-
advantage that per horse power, the
weight of a gas engine is so much
greater than that of a steam engine, and
cannot therefore at present be economic-
ally employed for tram cars.

Compressed air engines have been
employed with considerable success by
Col. Beaumont for driving tram cars,
and he has succeeded in storing in one
cubic foot of air at 1,000 lbs. pressure
per square inch enough energy to pull
three tons about half a mile along an
ordinary tramway. Bat successful as
this system is from the point of economy,
there is the same objection that there is
to the steam tram, viz., the comparative
great weight of the locomotive. The de-
tached compressed air engine weighs
about 7 tons, while the car full of pass-
engers is hardly 5 tons, so that seven-
twelfths of the total horse power ex-
pended is employed in pulling the com-
pressed air engine alone. I understand
it is proposed to build combined cars
and compressed air engines, a change
that will probably lead to a great im-
provement.

Vol. XXVII.— No. 1—5.

In order to obtain mechanical motion
we require a store of energy, and some
machine for converting the energy
stored into mechanical work. Now
experiment shows that the weight
of an electric motor is but a small
fraction of the weight of a small
steam engine and boiler per horse-power
developed. Electric motors, indeed, can
be easily made to give out work at the
rate of 1 horse-power per 50 lbs. dead
weight of machine, and hence the great
advantage of using them for movable
machinery. (Experiment shown of drill-
ing holes in thick wood with a hand elec-
tromotor and raising large boxes with a
small electric hoist.) The most econo-
mical store of energy we can convert
into mechanical energy by the agency of
electricity is evidently the energy of
coal, and this is the store we shall mainly
employ in driving electric motors. That
is to say, coal will be burnt to produce
mechanical motion, the mechanical mo-
tion will work a magneto or dynamo elec-
tric machine to produce an electric cur-
rent, the electric current, will be con-
veyed along the wires, and at the other
end, by means of an electro-motor, the
electric current will be reconverted into
■ mechanical work. (Experiment shown.)

Instead of converting the electric cur-
rent energy into mechanical motion I
can convert it into heat, and I shall then
have, as you see, the ordinary electric
light.

But if the engine breaks down, the
electric motor at the other end must
stop, or the electric light go out ; the
constant occurrence of which accident
has just decided the authorities at the
Manchester Railway Station to discon-
tinue the use of the electric light. To
prevent this effect following such an ac-
cident, an electric accumulator is needed,
that is a reservoir which has been drink-
ing in the electric energy when the en-
gine was going at its best, and which
will now give it out when the engine has
stopped. Again, apart from accidental
fluctuations in the speed of the engine,
' or total breakings down there is another
| most important use for the electric ac-
cumulators. That the electric lighting
of towns will become general, I need
hardly to stop to prove to you, and that
it will be carried out in ways quite differ-
I ent from the expedients temporarily

TAN NOSTRAND'S ENGINEERING MAGAZINE.

adopted is also equally obvious. But
users of electricity in this country have
at present to manufacture their electric-
ity as they require it, and are in the
same position that gas companies would
be in if they were unable to store their
gas, but had to manufacture it all while
it was being consumed. They would
evidently require much larger and con-
sequently more expensive plant. Now
the experience of two years has shown
that, for large buildings, the electric
light is far cheaper than gas. How much
cheaper will it then become, when the
electric energy can be manufactured at
any time convenient, and stored until it
is required tube used?

The earliest form of accumulator was
simply a voltameter worked backwards.
Now although Sir William Grove greatly
increased the efficiency of this secondary
battery by coating the plates with pla-
tinum black, still it was of little practical
importance because of the rapid escape
of the greater portion of the gases
formed, if the charging was continued
for a long time, as well as their diffusion
through the liquid.

It is clear, then, we must arrange mat-
ters so that the passage of the primary
current, forms on each plate a substance
which has no tendency to wander over
to the other. Such a substance must
obviously be a solid, and a solid not solu-
ble in the liquid. Now, an oxide of lead
satisfies, in a marked degree, these condi-
tions, and hence the employment in sec-
ondary batteries of this oxide, produced
usually by sending an electric current
between the lead plates immersed yi di-
lute sulphuric acid.

But, in addition to having the plates
near together, they must have large sur-
face, in order to store much electric en-
ergy. And the way to give the plate a
large surface, without making it incon-
veniently large, is to make it spongy.
Hence what is aimed at is two spongy
lead-plates near together.

Plante's method of accomplishing this
occupied some months, and even when
" well formed," his cell does not store
very much electric energy, so that it has
hardly ever been used for any commercial
purpose.

In 1880, M. Faure thought of the de-
vice of putting a thick layer of red lead
on his lead plates, a substance which can

easily be reduced to spongy lead by the
passage of a current. The plates, after
being coated with red lead, are then
wrapped in flannel jackets and put side by
side in a box, every alternate plate being
connected together, so as to practically
produce two plates with very large sur-
face very near together. To form the
cells, reverse currents are sent somewhat
the same way that they are sent in

forming the Plante cell, with the excep-
tion that only days and not months are
required in the formation. The red lead
on the one side is reduced to a spongy
material, which is probably lead very
slightly oxidized ; on the other side, it is
reduced to lead peroxide. Charging the
cell, by sending a current in the direction
of the last current sent, reduces the sub-
oxide to pure lead, and the lead perox-
ide, on the other side, to an even more
oxidized salt. On using the cell to pro-
duce an external useful current, the pure
spongy lead becomes again slightly more
oxidized, and the peroxide slightly less
oxidized. In fact, there is a small quan-
tity of oxygen which travels backwards
and forwards as the cell is charged and
discharged.

Now, does such a cell store electricity ?
No ! emphatically no ! When charging
it, just as much electricity passes out as
passes in, and, when discharging it, just
as much electricity passes in as passes
out.

Imagine a stream of water was turn-
ing a water-wheel, and the water-wheel
was employed to raise corn up into a
granary, the arrangement might be called
one for storing corn, but certainly not
one for storing water. So a secondary
battery does not store electricity, but
electric energy.

The pith, then, of Faure's discovery is
the mechanical placing of a salt of lead
on the leaden plates, the presence of
which layer of lead salt enables spongy
lead to be produced in a few days, in-
stead of requiring many months, when
the spongy lead is electrically formed
out of the lead plates themselves by the
long passage of electric currents.

The next point to consider is : (1) the
storing capacity of such an accumulator ;
(2) its efficiency ; (3) its durability. Now,
I am glad to say, I am able to give you
more than hearsay evidence on this point,
since Prof. Perry and myself have been

THE STOKAGE OF ENKK(iY.

<>?

engaged on rather a long series of experi-
ments on this subject I may mention

that we were both rather sceptical about
the merits of the Faure accumulator be-
fore commencing this investigation, since
we feared that the reports of its excel-
lent action were almost too good to be
true. Our doubts, however, gradually
dispelled themselves as the investigation
proceeded, and we now are able to add
our tribute to its practical value.

Let us take a single example of the
storing capacity. A certain cell, contain-
ing 81 lbs. of lead and red lead, was
charged and then discharged, the dis-
charge lasting eighteen hours — six hours
on three successive days ; and it was
found that the total discharge repre-
sented an amount of electric energy ex-
ceeding 1,440,000 foot lbs. of work. This
is equivalent to 1 horse power for three-
quarters of an hour, or 18,000 foot lbs.
of work stored per lb. weight of lead and
red lead. The large curve shows graphi-
cally the results of the discharge. Hori-
zontal distances represent time in min-
utes, and vertical distances foot lbs. per
minute of energy given out by the cell,
and the area of the curve therefore the
total work given out. On the second
day we made it give out energy more
rapidly than the first, and on the third
more rapidly than on the second, this
being done of course by diminishing the
total resistance in circuit. During the
last day we were discharging with a cur-
rent of about 25 amperes. But in con-
nection with the storing power, there is
a very curious phenomenon to which I
think not nearly sufficient attention has
been directed, and that is the resuscitat-
ing power of a Faure's cell. When a
cell has been apparently completely dis-
charged, and is left for a few hours by
itself, it appears to have obtained a new
charge. For example, after the eighteen
hours' discharge just referred to, al-
though there apparently was no electric
energy left in the cell at the end, it was
found that after a few hours' insulation,
the accumulator could give a current of
over 50 amperes, and produce therefore
bright flashes of fire. The phenomenon
is wonderfully like the invigorating ac-
tion of sleep. In one case, during our
experiments of an extremely rapid and
powerful discharge, we found that in sub-
sequent discharges after rest, the cell

gave out three times as much energy as
it did in the first discharge. The neglect
of considering this resuscitating power
has doubtless misled many people who
have possibly discharged a l<\iur< 's cell
very rapidly into under estimating its
; storing capacity.

Secondly, as regards efficiency. The
efficiency of an electric accumulator — that
is, the ratio of the work put into it to the
wrork given out — depends on the speed
with which it is charged, and the speed
with which it is discharged. If charged
or discharged too quickly, a certain
amount of energy will be wasted, heating
the cell itself ; since, whenever a current
passes through a body, some heat is de-
veloped, and the greater the current the
greater the heat, the latter indeed increas-
ing much more rapidly than the current.

• Now, it is possible, in a way I will not at
; the moment trouble you by explaining, to

distinguish between the work given to the
cell to produce chemical decomposition
and the work wasted by too hurried
charging. Similarly, in discharging, it is
also possible to find out how much of the
electric energy stored up in the cell is
wasted in heating it by too hurried dis-
charging. Allowing for such unnecessary
waste, experiment shows that, for a mil-
lion foot-pounds of stored energy dis-
charged with a mean current of 17
amperes, the loss in charging and dis-
; charging combined need not exceed 18
1 per cent.; indeed, in some cases, for very
slow discharges, we have found it not to
exceed 10 per cent. I do not, of course,
mean by this, as some people have mis-
takenly imagined from the published num-
; bers of Prof. Perry and myself, that a
1 current of only 17 amperes can be ob-
j tained by discharging a single cell ; since,
of course, far greater discharge-currents
; can be produced if the external resistance
| be low ; indeed, I shall show you a con-
stant discharge of about 70 amperes pres-
! ently. In speaking of the number 1 7, 1
! merely mean to say that was the average
current when the experiments on the
efficiency above referred to were made.

As to deterioration, two months con-
stant charging and discharging of the two
\ test-cells showed no signs of deteriora-
i tion.

I have said that a cell containing 81 lbs.
of lead and red lead stored 1,440,000 foot-

• pounds of work. Now, consider what

VAN NOSTRAND'S ENGINEERING MAGAZINE.

that means. It represents all the energy
required to be expended to pull a tram-
car containing forty-six passengers over
two miles, after allowing for considerable
waste of power in the electrical arrange-
ments. The electromotor and gearing-
need not weigh, as I told you, more than
about 200 lbs., to produce about two
horse power. We have, therefore, this
wonderful conclusion, that about 300 lbs.
dead weight contains all the energy and
all the machinery necessary for over two
miles' run of a tramcar with forty-six
passengers. Now, is this result actually
obtained at present in the tramcar running
at Leytonstone, and which is propelled
by Faure's accumulators 1 No, and why !
Partly because the electro motor has
not been made to suit the accumu-
lators, nor the accumulators the electro-
motor, nor is the gearing adapted to
either.

The cells, as at present made, would
not give off then energy quickly enough ;
hence a greater number are employed, but
which, consequently, require to be charged
much less frequently than would other-
wise be necessary. Indeed, in a ton of
the cells as at present constructed, there
is about fifty miles' run of *a tramcar con-
taining* forty-six passengers.

But, in spite of the temporary character
of this arrangement, the total weight of
the Faure cells, dynamo and gearing com-
bined, used at Leytonstone, is only 1^
tons, or one third of the weight of a de-
tached steam or compressed air engine
commonly used for tramcars.

Spacious as is the Lecture Theater of
the London Institution, it is unfortunately
not large enough to admit a tramcar. I
have therefore done the next best tiling
to prove to you that the Faure accumu-
lators really contain a vast store of avail-
able energy. We have here a circular
saw which is now cutting wood over an
inch in thickness. As you see, the cir-
cular saw is driven by that Gramme
electromotor, and the electromotor itself
is fed by the energy stored up in these
accumulators, and which was put into
them by a dynamo machine y ester day, on
the other side of London.

When the Faure's accumulator was first
invented, there were various suggestions
of electricity being delivered at houses
every morning like milk in cans, and the
exaggeration of this idea no doubt did

something to prejudice the cells in the
eyes of the public. The reason why milk
is delivered in cans and brought by carts
is simply because the total quantity re-
quired is so extremely small. If milk
were required to be consumed in large
quantities like water is, we should have it
sent through pipes, and not by cans.
The main use of the accumulators will be
as stationary reservoirs corresponding
with cisterns for water or gasometers for
gas. But in certain cases where the ac-
cumulators can be* used to proper a cart,
as in the case of tramcars, not the cart
employed solely to carry the accumula-
tors, then there is not the same objection
to then being moved about, seeing that
the total weight necessary is small com-
pared with that necessary for a steam-
engine or a compressed air engine for
tram Hues to develop the same horse
power.

Again, just as ordinary electromotors
are not made to discharge a Faure's cell
rapidly, so ordinary electric lamps are
unsuited for this purpose ; and, therefore,
although there is enough energy in a 100
lbs. dead weight of Faure accumulator, to
give a light of 1,500 candles for thirty
minutes, an ordinary electric lamp cannot
be illuminated at all by a single cell. Mr.
Edison, however, has been turning his at-
tention to this subject, and here is there-
suit of his handiwork, which arrived last
night from America, and which is, there-
fore, shown for the first time in England
this evening. This incandescent lamp, as
you see, only requires four Faure accumu-
lators to illuminate it, this one eight, and
this other one twelve. But must the ac-
cumulators be even as large as those I am
using on the table ? The answer is, No ;
if you do not require them to give out the
light for a very long time. Four much
smaller boxes would give just as much
light as you see at the present moment ;
but, of course, would not keep the light
burning so long. It is, therefore, now
possible to have a box of accumulators
and an incandescent lamp, and the whole
thing quite easily carried by one man.

Last year Prof. Perry drew attention,
in his lecture at the Society of Arts on the
" Future of Electrical Appliances," to the
great waste of energy that is produced by
the coal being carried to the steam engine,
instead of steam engines being brought
to the coal, and the power given out by

THE STORAGE OF ENERGY .

the engines conveyed electrically to the
place where it was commercially required-
Why, said he, should not the coal be
burnt at the pit's mouth, or in the pit, or
even in that part of the mine where the
seams were thickest, and the engines
driven by burning it used to work large
dynamo machines on the spot, and the
power transmitted electrically to any
towns where it was required .' Again, it
has been often asked, why should not the
wasted power in streams be utilized? At
present it is more economical to use
steam engines in a town than to do work
in the country by me ms of the streams,
and convey the manufactured articles over
the hills into the towns ; and for that
reason one sees the old water-wheels, in
the neighborhood of a place like Sheffield,
being gradually deserted, and the men
preferring to pay a higher rent for steam-
driven grindstones in the town, to a
smaller rent for water- driven grindstones
in the suburbs. The question then arises
would it be possible to convey economic-
ally the power from the coal pits or from
the streams into the towns by means of
electricity ; and this obviously turns on,
how much power can be got out of one
end of a wire compared with the amount
that is put in at the other ? I have, dur-
ing this evening, been talking of the
measurements of electric energy put into
or taken out of an accumulator of foot-
pounds, and you may have wondered howT
it was possible to measure electric energy
hi the engineer's unit of foot-pounds. In
reality it is very simple. The maximum
amount of work a waterfall can do, de-
pends on two things, the current of water
and the height of the fall. In the same
way, the work a galvanic cell or accumu-
lator can do, depends on two things, the
current it is producing, and what is called
its electromotive force, the latter being
analogous with the difference of pressure
or head of water. Again, when electric
energy is being turned into mechanical
work by means of an electromotor, the
energy which is being put into the motor
can be measured by the product of the
current sent through the motor, and the
electromotive force maintained between
the terminals of the motor. Now, here
are two instruments, devised by Prof.
Perry and myself, an Am meter and a Volt
meter, the one for measuring a strong
current, and the other a large electro-

motive force. With these we will now
make simultaneous measurements when
we allow this motor, which is driving the
lathe, and which is itself driven by an
electric current, to run at different speeds.
First, we will start with the motor, which
has one ohm resistance absolutely at rest,
by putting a brake on it, and ending by
allowing it to run as fast as possible.

Experiment performed and the follow-
ing results were obtained :

-a

0
Slow
Fast

a
<

QJ
U

■—

uat3

u o

2S
I jo z a

O I

■*-» — >

^ a

^ ■ s-

£ o %
o *e »

m» © g

o -j o
JO 13 Q*

o Qi a •

A A — .2

*" w * 3
<m o a

£»©-« u

u. % *- 3

£ ^ O O

—
99

=1 c
3 £ o ->

15 15
10 21

4| 28

15x15x44.25 152x 1x44.25
i.e. 9956.25 ie. 9956.25

10x21x44.25 10- x 1x44.25

i.e. 9292. 5 i.e. 4425
4x28x44.25 42Xlx 44.25
i.e. 4956 i.e. 708

We see in the last case, when the load
was light and the speed of the motor very
great, there was less than one-tenth of
the waste of power arising from the cur-
rent heating the wires when the speed
wTas very slow. On the other hand, we
observe that the electromotive force be-
tween the terminals of the motor has
been practically doubled.

This simple experiment really points to
the solution of economic transmission of
power by electricity, and to which Prof.
Perry and myself have on numerous oc-
casions directed attention. It is, to allow
only a very small current to pass through
the wires connecting the electro-motor
with the generator, and to maintain a
very great electro-motive force between
them ; since, in this wray, the amount of
power transmitted can be made as large
as we like, and the waste from the heat-
ing of the wires from the passage of the
current as small as we like.

Reasoning in this way, Sir W. Thom-
son showed, in his inaugural address last
year to the British Association, that, if we
desire to transmit 26,250 horse-power by
i a copper wire half an inch in diameter,
, from Niagara to New York, which is about
i 300 miles distance, and if we desire not

VAN NOSTRAND'S ENGINEERING MAGAZINE.

to lose more than one-fifth of the whole
amount of work — that is to deliver up in
New York 21,000 horse-power — the elec-
tromotive force between the two wires
must be 80,000 volts. Now, what are we
to do with this enormous electromotive
force at the New York end of the wires ?
Fancy a servant dusting a wire having this
enormous electromotive force. You might
as well, as far as her peace of mind is con-
cerned, ask her to put a lightning flash tidy.

The solution of this problem was also
given by Sir W. Thomson on the same
occasion, and it consists in using large
numbers of accumulators. All that is ne-
cessary to do in order to subdivide this
enormous electromotive into what may be
called small commercial electromotive
forces is to keep a Faure battery of 40,000
cells always charged direct from the
main current, and apply a methodical sys-
tem of removing sets of 50 and placing
them on the town supply circuits, while
other sets of 50 are being regularly intro-
duced into the main circuit that is being
charged. Of course this removal does not
mean bodily removal of the cells, but
merely disconnecting the wires. It is
probable that this employment of second-
ary batteries will be of great importance,
since it overcomes the last difficulty in the
economical electrical transmission of pow-
er over long distances.

I will conclude my lecture by illustrat-
ing one of the other important uses to
which the accumulator can be applied,
and that is the practical lighting of rail-
way trains, which may be seen in daily
operation in the Pullman cars on the
Brighton line. The most natural method
of lighting a railway train would be to at-
tach a dynamo-machine to the axle of one
of the carriages — the guard's van, for ex-
ample— and the rotation of which, neces-
sarily very rapid when the train is going
fast, would, without the use of any gear-
ing, produce the necessary current. But
the difficulty that immediately meets us is
that as soon as the train slows, or stops
at a station, or in consequence of the sig-
nal being against it, the speed of the
dynamo-machine will diminish and the
lights will go out. If, however, while the
train is going fast, the dynamo performs
two operations, the one to keep the lights
burning, the other to charge a battery of
Faure's accumulators on the train, then
the electric energy so stored can be ap-

plied to maintain the lights while the
train is going slowly or stopping. With
such an arrangement there would be, of
course, an automatic contrivance for dis-
connecting the dynamo-machine from the
circuit when the speed becomes too low ;
otherwise the Faure's accumulators would
simply discharge themselves back through
the dynamo-machine.

Imagine, now, we are in a train which
is going slowly, or which has actually
stopped, and that the Faure accumulators
lying here on the floor is the Faure bat-
tery in the train, and which has been
charged when the train was going fast ;
then that it has sufficient store of energy
to continue lighting is proved, because,
on connecting these two wires, those fifty
Maxim lamps, kindly lent me by the Elec-
tric Light and Power Company, and eight
Edison lamps before you, are instantly
brilliantly illuminated, each of the former
possessing about forty candle-power, and
each of the latter about seventeen, and
giving, therefore, far more light than is
at present ever supplied to a whole train
of twelve carriages. The light, you ob-
serve, is perfectly steady, and is turned
on and off at will. Imagine, now, we are
in a tunnel in the daytime, and the lights,
therefore, burning. We now emerge
from the tunnel into daylight. I discon-
nect the wires, and the lights are instant-
ly extinguished. Again, it may be, we
are entering a second tunnel. The wires
are again connected by the guard, and we
have the whole of this lecture theater,
which represents, the train, brilliantly
illuminated.

There has been an erroneous impres-
sion existing lately, that the Faure accu-
mulator could not produce a constant
current of more than 17 amperes ; but
that this is a mistake is clearly seen from
the fact, that at the present moment, each
of the cells in this room is producing a
current of about 75 amperes.

Electric storage of energy, therefore,
makes us nearly independent of accidents
to the engine or dynamo machine, or ir-
regularities in their working, enables us
to receive our supply of electric energy
from the central supply station in our
proper turn, and independently of the
particular time we require to utilize it,
and lastly it enables large amounts of
power to be transmitted over very long
distances with but little waste.

FORMATION OF SAND BANKS AND SAND HILLS.

ON THE FORMATION OP SAND BANKS AND SAND HILLS,
AND THE CONSTRUCTION OF HARBORS ON

SANDY COASTS.

By H..KELLKH.
Translated from "Zeitfchrift fur Bauwesen," for Abstracts of the Institution of Civil Engineers.

The author holds that all coast lines
are iii a continual state of change from
the action of the sea, the rate of varia-
tion being slower as the materials of the
land are more resisting, and the force of
the waves less great. The general effect
is to wear down promontories and fill up i
bays ; but to tliis there are many excep-
tions: thus the point of Dungeness has
advanced 90 yards in fifty-two years, j
Such cases are due to the action of spe-
cial currents, combined with low wave \
power.

Sandy Coast. — The rock and earth of |
the cliffs, after being shaken down by the
breakers, are by the same cause ground
into smaller and smaller fragments, till
they arrive at the state of sand. The
fragments are roughly sorted, according
to weight, by the carrying power of the j
waves, and when they have reached a
depth too great for direct wave action, |
the fiuer portions are still moved by the
currents. By studying the geological
character of the shingle and sand at va-
rious points of a coast, the direction of
its drift, and consequently that of the
prevailing currents, can generally be de-
termined.

Flat coasts, especially of the tertiary
and quaternary formations, are the chief
localities of sand, owing both to the large
area winch is acted on between high and
low water, and to the large horizontal
motion of waves in shallow water. At
the water's edge, where the waves are
finally spent, a flat and even strand is
formed; further down, where the ad-
vancing and retiring waves meet in con-
flict, the sand is violently agitated, and
heaped up into ridges, while during each
movement it is carried onwards for a
short distance by the set of the prevail-
ing currents. These currents, and the
sand they transport, pass straight across
the mouths of narrow inlets or bays, and
thus form bars or sand banks, which
often convert the latter into lagoons.

Similarly a row of islets may be con-
nected with each other, and with the
mainland, by accumulations derived from
such currents. The quantity of sand
thus transported, on any given sandy
coast, cannot easily be estimated.
Where harbors are choked by it, dredg-
ing operations, though useful in the case
of shingle, are of no permanent avail, in
consequence of the inexhaustible supply
of sand furnished by a long coast line ;
and no operations for cutting off this
supply are of much effect.

Influence of River Silt. — The mud
and sand brought down by rivers add of
course to the accumulation of sand
banks, though much of it is so fine as to
be carried at once into deep water. The
amount of this addition does not depend
so much on the quantity brought down
as on the coarseness of its quality, and
the effects of winds and currents at the
river mouth in causing it to settle near
or far from shore. The shingle is of
course deposited first, then the sand,
and lastly the mud.

Breadth of Quicksands. — Various ob-
servations seem to show that the zone
of quicksand, i. e., of sand continually
in motion, does not extend below the
point at which the direct or indirect ac-
tion of the waves ceases; its breadth is
therefore in general small.

Formation of Sand Banks. — Wher-
ever a current charged with silt has its
speed seriously reduced, deposition may
take place. The cause of such reduction
may be the meeting with an obstacle,
such as an island or wreck, the meeting
with another current, a change of direc-
tion, &c. Of these the second is the
most important ; the same cause which
makes the sand banks prevents their ris-
ing into islands, and they often become
very large. The two currents may be
both ocean currents, due to temperature,
or one an ocean current and the other
the outflow from a river.

VAN NOSTRAND S ENGINEERING MAGAZINE.

Effect of Storms. — Were the weather
always equable, the changes of a coast
line would be very slow, depending only
on the erosion of land by the sea and
by the rivers, and on the shifting of the
sand by currents ; storms, and k' storm
floods," by which is meant the heaping
up of the sea against the coast in heavy
landward gales, have, however, a very
great and disastrous effect in breaking
up sandy shores and sweeping away the
materials. The rounded outline of the
east coast of England, as compared with
the deeply-indented coast line of Fries-
land, is evidence in itself that in the Ger-
man Ocean the prevailing gales are from
the west. Such washing away of the
coast may be assisted by geological
causes, such as the yielding nature of the
strata, or a secular sinking of the land.
The result is the retreat of the land in
most places, often accompanied by an
advance elsewhere, where the materials
washed away are deposited. In many
places the latter has been largely assisted
by human enterprise in the way of re-
clamation.

Coast Currents. — The main causes of
ocean currents are differences of tempera-
ture ; but these differences are greatly
lessened in the neighborhood of land.
Apart from special local currents, such
as those flowing out of inland seas, the
main cause of powerful coast currents,
such as move sand and shingle, is the
wind. Such currents usually change
their direction as the wind shifts, and
the general drift of the sand is in the di-
rection of the prevailing winds. The
energy of waves driven by such winds
against the shore in an oblique di-
rection is expended partly in heat
and erosion, but mainly in mov-
ing the water, sand, &c, partly up and
partly along the beach. The latter move-
ment is the greater, as the wind is more
oblique to the coast line. Coast currents
thus formed have in some cases a speed
of 6 feet per second, and extend to a
depth of 30 feet, and it is these irregular
currents which mainly cause the move-
ments of sand and the formation of sand
banks.

In regions where the range of tide is
considerable, the currents of ebb and
flow add another important factor to the
causes of sand movement. They some-
times assist and sometimes oppose

the effects of wind currents and tempera-
ture currents, and have the greatest in-
fluence on shelving coasts, where that of
the waves is less than on flat coasts. The
periods of maximum velocity, both of
ebb and flow, the duration of each, &c,
are very much influenced by the peculi-
arities of different seas and estuaries,
and must be studied separately for each
case.

Formation of Sandhills. — When the
wind blows nearly perpendicularly on a
sandy coast it stirs up the dry sand, and
drives it onwards in successive bounds.
Where the sand is stopped by natural or
artificial obstacles sandhills accumulate,
which may be formed into regular chains
of " dunes." If an oblique wind from
the sea blows upon such dunes, it dis-
turbs their seaward face (unless it be
properly planted or fascined), and drives
the sand partly inland over the top, part-
ly along the face. In this manner thick
clouds of sand often travel along the
coast, and sometimes choke up the
mouths of streams, &c. Where there
are openings in the foremost dunes, the
sand rushes through, and forms other
dunes further inland. The sand of such
dunes is thus continually traveling, both
along the coast and inland — an evil
which can only be checked by planting
the dunes with vegetation, and by con-
tinual care. In some cases complicated
systems of dunes are built up by local
causes, and form sandy wastes of great
extent. The opposite effect, viz., the
blowing of sand into the sea by seaward
winds, is not usually of much import-
ance.

Action of Engineering Works on the
Coast-line. — The object of such works is
either the warding off of dangerous cur-
rents, or the causing sand to accumulate
at particular places, or the protection of
harbors. The first are only required in
places where the coast-line is in an. un-
stable condition, as at the mouths of riv-
ers. The second, such as groynes, are
intended to form deposits, as it were, of
sand, which may eventually check the
drift of sand under the action of coast
currents. They can only be very partial
in their operation, unless they are dis-
tributed over the whole length of coast
under treatment. Piers, projected into
the sea to protect harbors against the in-
cursions of sand, are generally acknowl-

FORMATION OF SAND BANKS AND SAND HILLS.

edged to be only of temporary advan-
tage ; since the sand gradually works
its way round them, even when they are
carried forward beyond the depth at
which coast currents usually operate.
Exceptions to this rule only occur where
some of the causes of sand movement
happen to be absent.

The direction which such piers should
take is not fully established. In recla-
mation works on rivers, a slight inclina-
tion against the current is known to be
best ; but for harbor piers a perpendicu-
lar direction may sometimes be prefer-
able. The object should be to divert the
sand moving along the shore into deep
water outside the harbor, by curves as
easy as possible, and allow it afterwards
to return to its general direction. The
angle between the pier and the coast al-
ways forms a sort of bay, in which the
waves tend to pile themselves up, and a
reflux is thus produced, which cuts out a
deep hollow along the pier. The sand
entering the angle is carried outwards by
this reflux, until it meets at right angles
the main coast current, wdiich has been
little influenced by the pier. At this
point the speed is checked, and sand de-
posited, which gradually forms a shoal
in the line of prolongation of the pier.
This shoal shelters the water between it
and the pier, and favors the deposit of
sand there ; so that eventually a compact
sandbank is formed round the head of
the pier, and extending some distance in
front of it. For these reasons an incli-
nation in the direction of the current
seems the best. The heaping up in the
angle is then less, and the sand comes
out at an angle to the coast current, and
mingling with it is carried forward with-
out settling. This will be facilitated if
the shape of the pier is made convex
towards the current, which at the same
time leaves the shore behind it quite open
to the sweep of the seas, and assists the
transport of the sand into deep water.
Whatever form is adopted, such harbors
will, however, always require a great deal
of dredging inside. The reason is two-
fold ; first, that the set of the flood tide
usually diverts the coast current into the
mouth of such harbors, and deposits the
sand in the still water ; secondly, that in
storms the waves fling masses of sand-
laden water into the harbor, with the
same result.

Thus at Boulogne the shoal of La
Bassure lies off the mouth of the harbor,
and leaves between itself and the coast
a narrow ami deep channel, to which the
shore falls in terraces. The Atlantic
tide- wave, coming in from the west.
causes strong currents along this chan-
nel in alternate directions ; and since, the
| new piers, now building, will be carried
out into this channel, it is hoped that
these currents will keep the entrance
always open, although dredging will no
doubt be required within the harbor.
On the other hand, the harbor of Ymui-
den, lately constructed with two piers in-
clined towards each o'ther, after the
model of Kingstown, already shows signs
of shoaling near the entrance.

Action of Scouring Currents 0)i the
Coast - line. — By a scouring current
(Spulenstrom) is meant any current
(generally that from a river or estuary)
which prevents the formation of sand-
banks by scouring them away as they
are deposited. Where the current is due
to a river, its effects will be greatly in-
fluenced by the amount of silt it carries
of itself, which may even turn it from a
scouring to a depositing current. Where
it comes from an estuary it is generally
clear, because the estuary forms a set-
tling basin, in which the silt is deposited.
In some cases the current may be due to
the reflux of the waters driven into a la-
goon by the wind ; but such entrances,
unless under very rare circumstances,
can never be permanent.

In the two former cases the scouring
is continuous, but varies greatly in in-
; tensity with the time of the year, height
: of tide, &c. The direct effect of a cur-
j rent of clear water is to drive outwards
| the coast current and the sand it carries,
which is gradually deposited in the form
of a concave bar round the mouth of the
river. This is usually cut through in one
or more places by narrow channels, its
form, &c, depending on the relative ac-
tion of the fresh water, the coast current,
and the prevailing wind. The outer side
of this bar is acted upon by the waves,
and when there is a gale full on them the
sands on this side are stirred up, and
carried over to the inner face of the bar,
or even into the harbor. By this means
the bar may sometimes be increased in
height, and moved towrards the harbor,
I in spite of the fresh water efflux. This

VAN N0STRAN1TS ENGINEERING MAGAZINE.

efflux can often be concentrated, and so
made more effectual, by the construction
of piers.

Currents entering the estuary from
the sea bring in silt, which is deposited
where the current dies away, i. e., in riv-

the whole of the tidal basin, outside the
actual low- water channels, arjd the con-
version of extended estuaries into flat
marshes, cut by deep and narrow
streams. These will often find their way
into the ocean by several mouths, espe-

ers at the upper limit of the tide, and in j cially when they carry much silt, and are

lagoons at the inner end of the connect-
ing channels, which thus gradually silt
up.

Where the upland waters are not clear,
but carry silt and shingle, things are al-
tered. The former mainly passes at
once into deep water ; the latter settles
first on the inner bar just described, un-
til a flood carries the whole of this bar
into the sea, where it goes to increase
the outer bar. This bar, gradually rising
on each side of the river channel, may
contract it so much that it may finally be
diverted, thus illustrating the formation
of deltas.

Action of the Tide in Estuaries. —
When the tidal wave is checked by en-
trance into an inlet or estuary, its for-
ward edge becomes higher and steeper ;
and where the rise of the bottom is rapid,
the depth small, and other circumstances
intervene, the regular form of the wave
is lost, and it rushes upwards as a
" bore." In the case of lagoons, the tide
advances more quietly, and generally de-
posits a good deal of silt ; occasionally
the ebb leaves the lagoon by a different
channel from that by which the flood has
entered.

The flood tide, pouring into an estu-
ary, brings with it sand and mud, of
which part at least is deposited where
the velocity comes to an end. Hence
the tidal area of a river is a sort of reser-
voir of silt, which oscillates up and down
till it either sinks permanently to the
bottom or is swept out to sea on the ebb.
In sheltered places sand banks and
islands are thus formed. The same tends
to take place outside the mouth of the
river ; but then such sand banks, after
having grown to a certain extent, always
come under the action of the coast and
other currents, and are cut back again.
The formation of sand banks or deltas
within the estuary, as described, tends
to form the same accumulations outside,
because it diminishes the tidal capacity of
the estuary, and therefore the power of
the ebb to scour these sand banks away.
The final result must be the filling up of

subject to violent floods, causing them
frequently to break open new channels.
Where, from such causes, an estuary falls
below its required width and depth, ar-
tificial works become necessary. The
object of such works should be to keep
the energy and volume of the ebb and
flow as great as possible at every part,
and at every time. The fall, section, sec-
tional area, and discharge of a stream
are all dependent on each other ; hence,
if the discharge be increased, the fall and
section will in general increase also, and,
if care is taken that the banks are not
attacked, the channel will be deepened,
An estuary, however, comprises two dif-
ferent parts — the tidal channel within
the river and the basin at the mouth —
and these require different treatment.
Parallel training banks are the right
method in the former, while in the latter
the object should be to cut off subsidi-
ary channels, and to concentrate the
flow.

Similar considerations appry to the
case of lagoons, which must in time either
be filled up entirely, or converted into
lakes, separated from the sea by banks
of shingle and sand.

Harbor Bars. — In the formation of
harbor bars, two forces besides the tide
are concerned, viz., the prevailing wind
and the coast current. Much depends
on the angle which the direction of these
make with each other. Where wind and
tide meet full against each other, the re-
sult is a stoppage of velocity and con-
sequent deposition of silt, combined with
a violent agitation or surf at the surface.
The bar is thus rendered doubly danger-
ous. The depth of the entrance will in gen-
eral be greater (as examples show) the
more inclined it is to the direction of the
waves. Hence the entrances of rivers,
in a stormy sea, are seen to take a direc-
tion more and more inclined towards the
coast, until at last the mouth gets choked
by the action of some storm, and the
river then breaks a new way straight
through the bar. For this reason break-
waters should be made convex to the

FORMATION OF SAND BANKS AND SAND HILLS.

direction of the wind, so as to give an
oblique direction to the current issuing
from the harbor.

The author then treats of the construc-
tion of harbors on sandy coasts.

Maintenance of Depth in Harbors. —
Most harbors on sandy coasts owe the
maintenance of their depth solely to the
scouring action of the estuary which
forms them. They are usually divided
into an inner harbor or dock, and an
outer harbor, often connected by a half-
tide basin. The outer harbor may be a
natural reach of river, as at Newcastle,
or an artificial basin. On sandy coasts
this basin will in general be in a con-
tinual state of silting up, and a bar will
be continually forming in front of it, as
already shown. All apparent exceptions
to this rule are either on large and power-
ful rivers or on rocky coasts. The in-
terior of the basin can be easily kept
clean by dredging, but the dredging of
the bar is a different matter.

For cleansing the interior, in cases
where the range of tide is great, artificial
scour is often resorted to. The water,
either tidal or upland, is impounded in
a basin, and let out through sluices
towards low water. As the issuing
stream has first to put the whole
water of the basin in motion, it is some
time before it reaches its maximum ve-
locity, and this period should be made to
coincide with that of dead low water.
The silting up of the scouring reservoir
itself is often a difficulty, which has not
been successfully met by admitting only
the upper and clearer layers of the tidal
water. If fresh water is used, rubbish,
logs of wood, &c, are collected in the
scouring basin, and eventually deposited
on the bar. The effect of such scour
does not reach below a depth of 6 to 9
feet, so that its power upon a bar is
limited. It is also inconvenient to the
ships using the harbor, and apt to under-
mine foundations, &c. This may be ob-
viated by placing the sluices outside the
half-tide basin, leaving the latter to be
cleansed by dredging. The effect of
scouring the harbor entrance itself has
not been fully tried, but works for this
purpose are in course of erection at
Calais and Honfleur. In such harbors
the piers are generally so long that it is
impossible to reach their outer ends by j
scouring from within (natural or arti- !

ficial), unless the resistance to the scour
is unusually small. To make it act with
effect on the bar, the pier should be
made concave to the scour, which will
run round it and then radiate outwards
to the place required. This is prefer-
able to training the current by low-
water walls, which impede the entrance
and cause surf. Movable training pon-
toons, moored in the tideway before
scouring, have been employed, but should
only be used for old harbors, where a
permanent pier cannot be had. A much
better mode of increasing the scouring
effect is to bend the channel as nearly
parallel as may be to the direction of the
waves and currents, as described above.
In general, with the view of assisting the
scour, all sharp turns, sudden changes of
section, and trumpet-shaped entrances
should be avoided, as these tend to
weaken the action of the current.

Action of Scour. — Lentz gives 0.75
meter (2J feet) per second as the lowest
velocity that will scour silt, and 1.50 to 2
meters (5 feet to 6| feet) as the lowest
that will scour sand. These are nearly
ten times as great as the corresponding
values given by Dubuat, &c, for river
water ; but the explanation is that the
former refer to the power of raising and
scouring away, the latter to the power
of transporting merely. Thus the first
of a series of scouring always has the
best effect, because it acts upon silt which
has only lately settled, and is easy to
move. Hence it comes that the artificial
scour is rarely useful at any great distance
from the sluices, because the velocity is
lost in causing eddies, and in putting the
surrounding masses of water in motion.
The remedy is to put the scouring basins
right at the mouth of the harbor, as men-
tioned above. To this the objections
are, the expense, and the fear of damage
by storms. To avoid this it has been
proposed by Bouquet de la Grye to lay
pipes, or a masonry culvert, from the
scouring basin along the pier, with sluices
at intervals, opening upon the entrance.
Another suggestion is that of Bergeron,*
to lay pipes along the bottom to the bar
itself, and use hydraulic pressure to stir
up the sand, which would then be carried
away by the ebb tide. The trials of this
promising method have not been sue

* Vide Minutes of Proceedings Inst. C.E., voL in.
p. 132.

VAN NOSTRANDS ENGINEERING MAGAZINE.

cessful, and the possibility of using it in
bad weather is very doubtful. Another
method also suggested by Bergeron, is
the use of vacuum dredgers, removing
the sand by suction, which work well
even in bad weather. These and other
mechanical means should only be con-
sidered as accessories to the scour, as-
sisting its erosion by forming a channel
for it. This has been done at Honneur
by planting a row of piles, or preferably
of buoys moored on to the bottom,
which, being agitated by the current,
form eddies and stir up the sand.

When artificial scour is employed, it
generally takes place only at spring
tides. The sluices are opened a little be-
fore low-water, and the scouring lasts
one and a half to two hours. This rarity
of action has a bad effect, as compared
with continuous natural scour, owing to
the opportunity given to the silt to settle
and harden. Moreover, the natural
scour of the ebb, which at least keeps
the silt in suspension, should be taken
advantage of. Artificial scour should
therefore be more frequent, begin ear-
lier, and continue till the turn of the
tide. Difficulties in the way of this can
be met by the same nfeans as before
suggested, viz., by making the discharge
basins and the sluices close to the en-
trance.

Arrangements of Harbors with regard
to Winds and Waves. — In many har-
bors the easy keeping open of the en-
trance is of less moment than the pro-
tection given from the sea, and the means
of safe entrance in all weathers. On
rocky coasts and in wide bays the works
required for this purpose are generally
simple, and consist in removing obstruc-
tions such as rocks, and building break-
waters to shelter the whole or a part of
the bay from the prevailing winds.
Where no bay exists, a harbor can be
formed by the building out of two piers,
with or without a breakwater in front of
the mouth. These piers should not have
salient corners, and should be convex,
not concave, towards the sea. The har-
bor should widen rapidly within the
entrance, so that the waves may spread
out and be lost, and vessels be at once
in safety. In designing the entrance,
the needs of vessels entering are of
course to be considered much more than
those of vessels leaving, especially in the

case of harbors of refuge. This does
not apply so much to harbors on flat
sandy coasts, as the depth at low water
is usually too small to enable them to be
used as harbors of refuge. Here it is
not so much storms which have to be
considered as the prevailing wind ; and
the entrance should be so placed that
vessels can make it without sailing at an
angle of more than 60° at the outside to
this wind. To lay the entrance directly
in line with this wind is not advisable.
It is quite unnecessary for sailing ves-
sels, especially in these days of steam
tugs ; the vessels entering come too
rapidly and those leaving are greatly im-
peded, while the harbor is exposed to
the full run of the waves, and the
scouring power of the ebb is much
reduced. Trumpet-shaped entrances
have also this last disadvantage, and in-
crease instead of diminishing the violence
of the waves. Whether the two piers
should be of unequal length must be de-
cided by local circumstances ; in general
the best arrangement seems to be that
the pier next the prevailing wind should
be shorter than the other, as this facili-
tates the entrance of vessels. The en-
trance should not be, if possible, per-
pendicular to the coast current, as it is
then harder to make, especially by long
vessels.

Artificial harbors have sometimes been
made with two entrances, but this is ob-
jectional. In some cases a single break-
water has been built across the mouth of
a bay, with an entrance in the middle ;
but this gives rise to bad cross seas be-
tween the impinging and reflected waves.
The outer ends of the piers should be
inclined towards each other at an angle
of about 90°, but not so as to be in a
straight line. The entrance should never
be exactly opposite the quarter of the
heaviest gales. This especially applies if
the outer harbor is to be used for un-
loading goods. When the entrance is
long and narrow, it is generally curved
gradually away from the direction of the
storms. The curve must be very gentle
if it is to accommodate the long ocean
steamers of the present day.

It is often impossible to attain to all
the above advantages, especially in chan-
nel harbors, as opposed to artificial ba-
sins. In the former the waves are some-
times broken up to some extent by inter-

THE THEORY OF THE GAS ENGINE.

posing jetties of open pile work, with
ride basins behind them. It has been
found advantageous to make the piers
themselves open above low water. On
the Tyne and elsewhere the mouth of the
estuary has been partly closed by piers,
thus forming- a sort of basin behind
them. This, from its preventing the
ingress of the tide, will probably
lead to silting up near to the mouth,
though in the case of the Tyne the im-
mense dredging operations higher up
tend to remove this difficult} .

After recapitulating the conclusions
arrived at, the paper gives a general pro-
ject for a tidal harbor on a sandy coast.
The points of first importance are pro-
tection against waves, convenience of
scouring, and prevention of excessive ac-
cumulations of the sand traveling along
the coast in the direction of the prevail-
ing winds. The pier exposed to this
sand must be long and convex, thus in-
closing a sort of basin within it. This
should be turned into a scouring basin
by means of an inner pier run out from
the shore with a slight curve to meet
the other or windward pier close to

the entrance. At the point of meeting
the sluices will be placed. Between this
third pier and the leeward pier will be
the entrance to the inner harbor, which
will thus have a channel form. The third
pier may be pierced by a Dumber of
openings, closed on the ebb but open
on the flood, which will tend to dissipate
the waves as they enter the harbor, dur-
ing the time of high water, when the
traffic is heaviest. The entrance will be
inclined as much as possible to the pre-
vailing wind, and the scouring opera-
! tions will take place on every tide, and
j be continued as long as possible, so as
to hinder the silt from settling, or stir it
up before it has become compact. By
such means the bar continually formed by
the advance of the sand will be as con-
tinually swept away into deeper water.
While the construction of these works
will no doubt be costly, the depth will
thus be permanently preserved at the
least possible cost.

The paper contains sixteen plans o
harbors, &c, and a great number of ref-
erences to particular cases, which for the
sake of brevity have been omitted.

THE THEORY OF THE GAS ENGINE.

From "English Mechanic and World of Science."

At the meeting of the Institution of
Civil Engineers held last week, a paper
by Mr. Dugald Clerk was read, " On the
theory of the Gas Engine." The prac-
tical problem of the conversion of heat
into mechanical work had been partially
solved by the steam engine ; but its
efficiency was so low that it could not be
considered as complete or final. Hot
air in the past had been looked upon as
a possible advance. Owing, however, to
many futile attempts, it had long been
deemed useless to look in that direction
for better results. The great progress
made in recent years with the gas engine,
from the state of an interesting but
troublesome toy to a practical powerful
rival of the steam engine, had shown
that air might, after all, be the chief
motive power of the future. Three dis-
tinct types of gas engines have been pro-
posed :

1. An engine drawing into the cylinder
gas and air at atmospheric pressure for a
portion of its stroke, cutting off communi-
cation with the outer atmosphere, and
immediately igniting the mixture, the
piston being pushed forward by the
pressure of the ignited gases during the
remainder of the stroke. The instroke
discharged the products of combus-
tion.

2. An engine in which a mixture of
gas and air was drawn into a pump, and
was discharged by the return stroke into
a reservoir in a state of compression.
From the reservoir the mixture entered a
cylinder, being ignited as it entered, and
without rise in pressure, but simply in-
creased in volume, and following the pis-
ton as it moved forward, the return
stroke discharged the products of com-
bustion.

3. An engine in which a mixture of

VAN NOSTRAND S ENGINEERING MAGAZINE.

gas and air was compressed or intro-
duced under compression into a cylinder,
or space at the end of a cylinder, and
then ignited while the volume remained
constant and the pressure rose. Under
this pressure the piston moved forward
and the return stroke discharged the ex-
haust.

Types 1 and 3 were explosion engines,
the volume of the mixture remaining
constant while the pressure increased.
Type 2 was a gradual combustion engine,
in which the pressure was constant but
the volume increased. Calculating the
power to be obtained from each of these
methods, supposing no loss of heat to
the cylinder, it was found that an engine
of type 1 using 100 heat units, would
convert 21 units into mechanical work ;
in type 2, 36 units ; and in. type 3, 45
units. The great advantage of compres-
sion was clearly seen by the simple oper-
ation of compressing before heating, the
last engine giving for the same expendi-
ture of heat 2.1 times as much work as
the first. In any gas engine, compress-
ing before ignition, igniting at constant
volume and expanding to the same vol-
ume as before ignition, the possible duty
D was determined by the atmospheric
absolute temperature T', and the ab-
solute temperature after compresssion,
T ; and it was D = T - T' | T, whatever
might be the maximum temperature after
ignition. Increasing the temperature of
ignition increased the power of the en-
gine, but did not cause the conversion of
a greater portion of heat into work. That
was, the possible duty of the engine was
determined solely by the amount of com-
pression before ignition. Compression
made it possible to obtain from heated
air a great amount of work with but a
small movement of piston, the smaller
volume giving greater pressures and thus
rendering the power developed more
mechanically available. Seeing the great
difference produced between types 1 and
3 by the simple difference in the cycle
operation when there was no loss of heat
through the sides of the cylinder, the
question arose, Which engine in actual
practice, with the engine kept cold by
water, would come nearest this theory ?
In which of the engines would there be
the smaller loss of heat ? Comparing the
two engines, with equal movements of
piston, it was found that the compression

engine had the advantage of a lower
average temperature and a greater
amount of work done ; also of less sur-
face exposed to flame, and consequently
it lost less heat to the cylinder. Taking
all the circumstances into consideration,
it was certainly not over-estimating the
advantages of the compression engine to
say, that it would, under practical con-
ditions, give for a certain amount of heat
three times the work it was possible to
get from an engine using no compres-
sion.

It was interesting to calculate the
amounts of gas required by the three
types under the supposed conditions.
Taking the amount of heat evolved by
one cubic foot of average coal gas as
equivalent to 505,000 foot-pounds, and
calculating the gas required if all the
heat were converted into work, it was
found to be 3.92 cubic feet per H.P. per
hour. Therefore, the amounts of gas re-
quired by the three types of engine
would be : —

3.92
Type 1. -r^r- =18.3 cubic ft. per HP. perhr.

U. J-lL

Q QO

« 9 —10 Q " " "

A0.36~- r

Q QO

" q "u — o a u a u

Comparing these figures^with results ob-
tained in practice from the three types
of engines losing heat through the sides
of the cylinder, it was ascertained that
the amount of gas consumed Was as
follows: —

Typ

3 1. Lenoir,

95 c

.ft.

per

I.H.P.

per hr.

Hugon,

2. Brayton

,50

3. Otto,

It would be seen that the order of con-
sumption was what was required by
theory. The Otto engine . converted
about 18 per cent, of the heat used by it
into work, while the Hugon engine only
converted 3.9 per cent. Taking the loss
of heat to the cylinder, as given by the
comparison of the adiabatic line of fall
of temperature with Ijhe actual line of
fall as shown on the indicator diagram,
it appeared much less than really was the
case, as shown by the gas consumed by
the engine. The maximum pressure pro-
duced was much less than would be ex_

TflE THEORY OF Till: i..\s IN (.INK.

71)

peoted from the amount of gas present ;
this was due to the limiting- effect of
chemical dissociation. The gas engine
presented a more complicated problem
than a hot-air engine using air heated to
the same degree. Analyzing the dis-
posal of 100 heat-units by Clerk's gas-
engine, it was found to convert 17.8 into
work, to discharge 29.3 with the exhaust
gases, and to lose to the sides of the
cylinder and piston 52.9 units. About
one half of the whole heat used passed
through the cylinder and heating water.
St. Claire Deville had shown that water
was decomposed into its constituents at
a comparatively low temperature, con-
siderable decomposition taking place at
1.200° Centigrade. The cause of so near
an approach to the line of theoretical fall, j author could not concur.

Bible to ignite a whole mass in any given
time, between t he limits of one-tenth and
one-hundredth part of a second, by ar-
ranging the plan of ignition so that some

mechanical disturbance! by the entering
flame was permitted. A diagram taken
from the Otto and Langen free-piston
engine, as given in a paper by Mr. F.
W. Crossley, and an analysis of his
reasoning, showed that the results were
misinterpreted, and false conclusions ar-
rived at concerning the nature of an ex-
plosion. Mr. Crossley considered that
an explosion of gas and air, pure and
simple, must be accompanied by a rapid
rise and an almost instantaneous fall of
pressure. This, he thought, was proved
by the diagram, but in this statement the

as was shown by the actual indicator
diagram, was simply the continuous
combination of the dissociated gases.
At a maximum temperature of about
1,600° Centigrade, complete combination
of the gases with oxygen was impossible,
and could only take place when the tem-
perature fell low enough.

In calculating the efficiency of the gas
engine from its diagram, all previous ob-
servers had fallen into error, through ne-
glecting the effects of dissociation, and,
accordingly, their results were much too
high. To account for this so-called sus-
tained pressure, Mr. Otto had advanced
the theory that inflammation was not
complete when the maximum pressure
was attained at the beginning of the
stroke, but that by a peculiar arrange-
ment of strata he had made it gradual,
and continued the spread of the flame
while the piston moved forward. Mr.
Otto called it slow combustion. This
designation seemed to the author to be
erroneous ; such an action should rather
be called slow inflammation. It existed
in the Otto engine, but only when it was
working badly, and was attended with
great loss of heat and power. This was
proved by a diagram, and by certain con-
siderations deduced from Bunsen and
Mallard's experiments on the rates of
propagation of flame through combust-
ible mixtures. The conclusion arrived
at was that slow inflammation was to be
avoided in the gas engine, and that every
effort should be made to secure complete
inflammation at the beginning of the
stroke. The author had found it pos-

From the considerations advanced in
this paper, it would be seen that the
cause of the comparative efficiency of the
modern gas engines over the old Lenoir
and Hugon type was to be summed up in
the one word "compression." Without
compression before ignition an engine
could not be produced giving power
economically and with small bulk. The
mixture used might be diluted, air might
be introduced in front of gas and air, or
an elaborate system of stratification
might be adopted, but without compres-
sion no good effect would be produced.
The gas engine was, as yet, in its in-
fancy, and many long years of work were-
necessary before it could rank with the
steam engine in capacity for all manner
of uses. The time would come when
factories, railways and ships would be
driven by gas engines as efficient as any
steam engines, and much safer and more
economical of fuel. The steam engine
converted so small an amount of the heat
used by it into work that, although it
was the glory and the honor of the first
half of this century, it should be a stand-
ing reproach to engineers and scientists
of the present time, having constantly
before them the researches of Mayer
and Joule.

The boring of the Arlberg tunnel is
proceeding rapidly, the rate of advance
averaging ten meters daily which exceeds
the average made with the St. Gothard
by six meters. At this rate boring is ex-
pected to be completed before the end
of 1883.

VAN NOSTRAND'S ENGINEERING MAGAZINE.

REPORTS OF ENGINEERING SOCIETIES

nrp ngineers' Club op Philadelphia —
Jjj Record of Business Meeting, May 6th,
1883.

The memorial to Congress of the American
Metro! ogical Society, asking for the adoption
of means by which a common mer.dian might
be established for the reckoning of longitudes
and local time, was presented and unanimously
approved. The pamphlet from the American
Society of Civil Engineers, upon .Standard
Time "for the United States, Canada and
Mexico, accompanied by questions to inter-
ested persons with regard to the various propo-
sitions, was presented and discussed.

The objects set forth in House Bill number
H. R. 4726, were unanimously approved and a
Committee appointed to transmit to our Mem-
bers of Congress the sentiment of the Club
upon this subject, and to take such action as
might best further the interest in this Bill.

Mr. Russell Thayer exhibited a section of an
underground conduit for electric light, tele-
graph or telephone wires.

Description. — This conduit consists of a box
or pipe made of terra cotta, artificial stone or
porous earthenware (in sections) glazed on the
out-ide and saturated with paraffine or crude
petroleum. (In the sample the paraffine is not
properly introduced, it should be saturated
into the pores of the material in a liquid state
while the material is warm and the paraffine
melted. The conduit should not simply he
coated with paraffine.) The box is made in
two parts divided horizontally, the upper por-
tion serving as a lid or coveT to the lower part,
and the lower part is constructed with grooves
or depressions running longitudinally, for the
reception of the wires. The sections are placed
in the ground and joined and cemented to-
gether with rings, and laid like an ordinary
terra cotta pipe.

Advantages: — This form of conduit possesses
the following advantages, viz. : it is very in-
expensive and very durable, indeed permanent
in its character. It is easily made and can be
laid by ordinary laborers. Being made in two
parts (an upper and a lower) there is no diffi-
culty whatever in placing the wires in it, and
if a wire should from any cause become dam-
aged or be defective at any points in the con-
duit, it is entirely accessible, since the cover
can readily be removed from any section, the
wire will be repaired and the cover be replaced.
The wires do not have to be pulled or forced
through a loner tube or pipe as has been done
heretofore. Electric light or telegraph wires
already placed on poles, can be transferred to
this conduit without breaking the circuit or
disturbing the current for a moment, since
being made in two parts, the conduit can be
placed in the ground, the wires be transferred
thereto, the lid be placed thereon, and the
trench be filled and the street be repaved as
fast as the pipe or conduit is laid. This is
obviously impossible to perform with a con-
tinuous pipe, tubes or arrangements of that de-
scription.

It can be constructed of any reasonable size

to hold any number of wires, and the wires are
completely insulated from each other by the
paraffine or crude petroleum with which the
material of the conduit is saturated. The sat-
urating material also prevents the entrance of
j water or moisture into the conduit. A patent
for this conduit has been applied for.

Mr. Thayer also presented the following:
While the subject of the construction of new
| bridges across the Schuylkill river is being con-
| sidered by Councils, I desire to record an ob-
[ servation relative to their design which I think
could, with advantage, be considered. It is
j simply this. There appears to be no good
j reason why the bridges built across this stream
! should be raised to such a great elevation above
the water level At their present elevation the
bridges are a complete obstruction to the pass-
] age of ships that cannot lower their masts;
| and it certainly seems to me that any new
structures that are built, could be lowered con-
siderably and at the same time not interfere
with the traffic on the river any more than at
present. The only change necessary would be
that the tugs and steamers would be obliged to
hinge their stacks so that they could be low-
ered while parsing under t he arches . Some of
the most celebrated stone bridges in the world,
viz.: those constructed by the French engi-
neers across the Seine at Paris, are almost all
low structures, with the roadway nearly level
transversely, and their stability and beauty of
architectural effect have caused them to become
models for similar structures in all parts of
the world. The advantages of constructing
bridges in the manner suggested are apparent,
and may be briefly stated as follows, viz.:

1. Economy.

2. Greater stability .

3. Better approaches.

Economy. — Because less masonry is required.

Greater friability.— Because there would be less
weight bearing upon the foundations from the
piers; and also because if there is any hori-
zontal or oblique resultant of force tending to
push the pier out of the vertical, the level arm
of said resultant in a low pier is much less than
of a high one.

Better Approaches.— -Because from the con-
figuration of the ground on either bank of the
river, the grades are more suitable for a low
bridge than for a high one. As at present
constructed, the grades on either sides of the
bridges are very steep, and when the pave-
ments are slippery they are almost unscalable.
Now, were the bridges not raised so high
above the water, the roadways over 4hem
would be a much more easy gradient. Indeed,
it seems to me, that they might with advantage
be made quite flat; not, however, on a dead
level, as I think a flight rise in the center of
the structure is desirable, on account of drain-
age and architectural effect.

I have briefly referred to this subject as the
matter seems to be one of interest at the pres-
ent time, aud if new bridges are to be built,
that design should be adopted which, con-
sidering all conditions and requirements, would
be the best for the locality in question.

i:v;in BERING NOTKS.

May 90th, L888.

Vice-President Perciva] Roberts, Jr., in the

chair.

Mr T. M. Cleemano read b paper on the
• Host Economical Eeighl of Bridge Truss."
Be said lhat in most cases of bridge design,
after the Bpan was tixiul. the height of the truss
was only governed by the judgment of the
engineer, who generally assumed a proportion
derived from sonic previously constructed
bridge. It is not difficult, however, to ti nil the
most economical height, ami the method ap-
plied to a Howe bridge was explained, and
the result of a similar application to one of the
largest iron bridges heretofore constructed like-
stated.

He also continued Borne remarks'that he had
previously made on the strength of wrought
iron columns, especially discussing certain ex-
periments which had been lately made at
Watertown, with the formulas that had been
proposed to represent their strength.

The latter paper was discussed at some length
by Messrs II. Constable, Strong, Haupt and
P. Roberts, Jr.

Mr. Geo, S. Strong gave an interesting illus-
trated description of experiment in the appli-
cation of his Feed-Water Heater to locomotive
engines, and also described new devices of his
inventiou, for the piston and connecting rods
of locomotives and for a spark arrester.

American Society of Civil Engineers.
—The Annual Convention of the So-
cietv was held at Washington, May 16th and
19th.

The principal papers read were —

An Instance of Zymotic Disease in Metals.
By O. E. Michaelis.

Subaqueous Underpinning. By A. G. Meno-
cal.

Overflow of the Mississippi River. By Ly-
man Bridges.

The Hudson River Tunnel. By Wm. Sooy
Smith.

Other papers presented but not read for want
of time were —

Experiments on the Flow of Water. By A.
Yteley and F. P. Stearns.

Targets for Rifle Ranges. By O. E. Micha-
elis.

Accuracy of Measurement as increased by
repetition. Bj- S. 8. Haight.

Highway Bridges. By James Owen.

The following important reports of com-
mittees previously appointed were read and
discussed :

Upon a Uniform System of Tests of kCe-
meuts.

Upon the Preservation of Timber.

The address of President Welch delivered on
the 16th we shall reprint in the August issue
of this Magazine.

ENGINEERING NOTES.

rpHE Bridge Across the Firth of Forth.

L — The Select Committee of the House of

Commons has passed the bill authorizing the

construction of a bridge across the Firth of

Vol. XXVII.— No. 1^6.

Forth at Queensfeny, with the stipulation that
the bridge La to be constructed under the super-
intendence of an officer appointed by the Board
Of Trade The proposed new bridge is in sub-
stitution of the one sanctioned in L878, ac-
cording to the designs of the late Sir Thomas
Bouch, Inasmuch as it will be a steel girder
bridge, instead of a suspension bridge, while
in strength and stillness it is calculated to sus-
tain a rolling-road three times greater and a
wind pressure live times greater than was at
first intended. The substituted bridge has
been designed by .Mr. Fowler, C.E., assisted by
Mr. T. E. Harrison, chief engineer of the
North-Eastern Railway, and Mr. Barlow, chief
engineer of the Midland Railway, whose plans
have been submitted to a committee of the
Board of Trade, consisting of Col. Yolland,
General Hutchinson and Major Marindin, who
are satisfied with the provisions made as re-
gards strength and stability. The bridge,
which is almost a mde in length, will consist
of two central spans of 1,700 feet and two side
spans of 675 feet, approached on each side with
spans varying from 115 feet to 150 feet. The
clear height above high water is to be 150 feet
for a width of 500 feet at the center of each
1,700 feet opening, and is intended to carry a
double line of rails throughout. The cost of
the construction is estimated at £1,730,000, and
the time allowed in the bill for its completion
is limited to five years. — Iron.

The Sahara Inland Sea.— The French
Government have recently bestowed great-
er attention upon the project, which has been
before the public for several years, of connect-
ing the depression of Rharsa and Melrirh, in
the Northern Sahara, by a sea canal with
the Mediterranean. The basin in question,
probably a dried-up salt lake, has an elevation
much lower than the level of the Mediter-
ranean, the depression being in some places as
much as 165 feet below that level. It is pro-
posed to admit the sea-water into this natural
basin, which covers a surface seventeen times
the aiea of the Lake of Geneva, by a canal,
starting from the Bay of Gabes, 33 feet deep
and 330 feet wide, of a total length of 150
miles. In order to reduce the heavy expense
attaching to the construction of such a canal,
it is to be made at first of smaller dimensions,
leaving the remaining work to be done by the
flow of water. The benefits which France will
derive from such a work are evident. It is ex-
pected that the canal and the inland sea would
favorably change the climate of that terribly
sterile region, improve French trade with Al-
geria and the Soudan, and confine the hostile
irruptions of the Sahara tribes. But serious
apprehensions are felt as to the success of the
undertaking, which has been planned by Major
Rondaire. It is especially feared that, on ac-
count of defective circulation, the process of
evaporation would involve a constant inflow
from the Mediterranean, which would soon
surcharge the new inland sea with salty matter,
and in that case destroy all existing organic
life, thus converting it into another Dead Sea
The French Government, in order to arrive at
a true solution of the problem, have appoint

van-nostkand's engineering magazine.

ed a commission charged with thoroughly in-
vestigating the question of this inJand sea. Its
report will be looked forward to by all inter-
ested in the matter.

IRON AND STEEL NOTES.

EXPERIMENTS ON THE STRENGTH OF
Wrought Iron and Steel at High
Temperatures. By C. R. Roelker.— This
paper contains no original matter, but is
an interesting summary of previous investi-
gations. Kollmann's experiments at Ober-
hausen included tests of the tensile strength
of iron and steel at temperatures ranging
between 70 and 2,000 degrees Fahrenheit,
and the mode of conducting these tests is de-
tailed in the paper. Three kinds of metal were
tested, viz., fibrous iron having an ultimate
tensile strength of 52,464 lbs., an elastic strength
of 38,280 lbs., and an elongation of 17.5 per
cent. ; fine grained iron having for the same
elements values of 56,892 lbs., 39,113 lbs., and
20 per cent. ; and Bessemer steel having values
of 84,826 lbs., 55,029 lbs., and 14.5 per cent.
The mean ultimate tensde strength of each ma-
terial expressed in per centum of that at ordi-
nary atmospheric temperature is given in the
following table, the fifth column of which ex-
hibits, for purposes of comparison, the results
of experiments carried on by a committee of
the Franklin Institute in the years 1832-36.

Fibrous

Fine

Temp.

Wrought

grained

Bessemer

Franklin

Fahr.

Iron.

• Steel.

Institute.

Per cent.

100.0

96.0

100

100.0

102.0

200

100.0

100. 0

105.0

300

97.0

100.0

106.0

400

95 5

100.0

106.0

500

92.5

98.5

104.0

600

88.5

95.5

92.0

99 5

700

81.5

90.0

68.0

92.5

800

67.5

77.5

44.0

75.5

900

44.5

51.5

36.5

53.5

1000

26.0

36.0

31.0

36.0

1100

20.0

30.5

26.5

—

1200

18.0

28.0

22.0

—

1300

16.5

23.0

18.0

—

1400

13.5

19.0

15.0

—

1500

10.0

15.5

12 0

—

1600

7.0

12.5

10.0

—

1700

5.5

10.5

8.5

—

1800

4.5

8.5

7.5

—

1900

3.5

7.0

6.5

—

2000

3.5

5.0

—

Comparing Kollmann's results with those of
Fairbairn, Styffe, and the British Admiralty,
and the author finds that the former differ
from the latter in respect of there being found
no increase of strength at temperatures higher
than the ordinary atmospheric temperatures. —
Proceedings Inst. Civil Engineers.

C Corrosive Effects of Steel on Iron in
J Salt Water.— This paper read before
the Naval Architects by Mr. J. Farquarson,
detailed an experiment designed to ascertain
the relative corrosion of iron and steel, and the

corrosive effect on these of the combination
when immersed in sea water. Plates of iron
and steel of equal size, with an aggregate
surface of 48 superficial feet, were used. After
having the scale completely removed by dilute
hydrochloric acid, they were singly weighed,
marked, and placed in a grooved wooden frame,
parallel and 1 inch apart, iron and steel alter-
nately. The first, third, and fifth pairs were
electrically combined by straps of iron at the
tops; the second, fourth, and sixth pairs being
left unconnected, and therefore each plate of
which was only subject to ordinary corrosion,
as if no other metal existed. The whole series
so arranged were placed in Portsmouth Har
bor, and left undisturbed for six months, when
they were taken up and again weighed. The
loss of each plate was found to be as under: —

Oz. Grains.

Steel / ■ , . A 0 427

Iron [combined ? m

Steel 3 340

Iron 3 327

Steel ) . . -, 0 297

Iron Combined 7 ^

Steel 4 0

Iron 3 190

Steel ) , . -, 2 337

Iron combined 6 Q

Steel 4 157

Iron 4 57

From the above it will be seen that the three
iron plates combined with steel lost 21 oz.
57 grs. ; that the three similar iron plates not
combined lost only 11 oz. 137 grs. The plates
were identical in size and all cut from the same
sheet, the effect of combination with steel
being to nearly double the loss of weight. The
proof that the great excess of loss was not due
to anything in the places themselves will be
clearly seen by comparing the combined and
uncombined steel plates, thus: — The three com-
bined with iron lost only 4 oz. 187 grs. ; the
three uncombined lost 12 oz. 60 grs., or nearly
three times as much as those protected electric-
ally by the iron.

Steel Plates for Boilers. — In 1879 the
French congress of engineers refrained
from pronouncing definitely on the relative
value of steel and iron plates for boilers, being
of opinion that the question was not then ripe
for decision. The fifth congress, which re-
cently met at Lyons, has once more inquired
into the subject, and has submitted, according
to the Bulletin of the Association parisienne des
Proprietaires d'Appareils a vapeur, the follow-
ing report : — Two boilers ordered by the Midi
Company of the Fives-Lille Works burst at the
trial, and the company consequently decided
not to use steel plates, notwithstanding that
Creusot offered every guarantee for its boilers.
The Forges et Chantiers de la Mediterranee
have likewise excluded steel plates from boilers.
Krupp has also given up steel, and the experi-
ments made at the instance of the English Ad-
miralty have shown that steel corrodes more
quickly than iron. This corrosion is all the more
dangerous,as steel plates are used much thinner
than iron plates. Mr. Webb, of Crewe, not-

ORDNANCE AM) NAVAL.

withstanding, still adheres to the application
of steel plates tor the engines of the North-
Western Railway. The engineers of Rouen
also employ steel plates, on the ground, pre-
sumably, that they would prove more homo-
geneous in ease of overheating. But this ad-
vantage is. according to M. Roland, of too
small account compared with the great draw-
back that they arc very liable to tear and hurst
at the ends ami in the rivet holes either during
manufacture or during use. He cites in sup-
port of his views the case of the eight boilers
made by Messrs. Elder and Co. for the Livadia,
of which three burst at a pressure of 3.V to (>£
tons per square inch, the result being the re-
>n of all the boilers. M. Cornut expressed
the prevailing opinion of the congress when he
Stated that at present steel plates do not offer
sufficient safety for the construction of steel
boilers, and that it would be advisable not to
employ them. He assumes that an amount of
care would be required in the manufacture of
steel used for this purpose which few makers
^ould be inclined to exercise, and that to this
circumstance must be ascribed the many fail-
ures observed in this department of the use of
steel. — Iron.

ORDNANCE AND NAVAL.

V^ ubmarine Warfare. — Engineering science
O is still actively engaged upon devising
means for the most rapid and effectual destruc-
tion of an adversary in naval warfare. A new
submarine torpedo boat, the invention of M.
Dgevetsky, has recently been tried at Kron-
stadt. Itis a very small boat, about 20 feet in
length, and weighs, when fully equipped, not
quite two tons. The boat has the form of a
cigar; its screw propellor is moved by the feet
of four men placed in the central part of the
vessel beneath a small glass dome through
which the officer in command can see the sub-
merged portion of the enemy's vessel, and ac-
cordingly direct the attack. The speed attain-
able by "this boat is four miles an hour, which,
it is considered, is amply sufficient to enable a
subaqueous attack to be made upon vessels
lying at anchor or approaching. The steerage
of the boat presents no difficulty. To lowrer it
to the distance of 50 feet and to raise it again
to the surface of the water is rendered an easy
operation by a very ingenious device. This
elevation or depression is effected by means of
weights made to slide upon longitudinal, hor-
izontal bars or guide rails. When the boat is
fully stored, charged and equipped, its normal
position is just beneath the surface of the water,
the upper portion of the glass dome alone
slightly emerging. When it is desired to sink
to a certain depth, the weights are slid forward
to the prow of the boat, which, upon the pro-
pellor being set in motion, immediately begins
to descend. The depths attained are shown by
a specially constructed manometer. As soon
as the boat has reached the desired depth, the
weight is moved back to the center of the boat,
and the latter now takes a horizontal direction.
In order to rise to the surface, the weight is
slid back to the stern, and thus an upward di-

rection is communicated to the motion of the
boat. Each of these boats is provided with a
couple of mines or torpedoes, attached to it by
means of levers. As soon as the boat pusses
Underneath an enemy's ship, these can be in-
stantly detached, and are so constructed as to
mount upwards, and, by means of a gutta -pei
Oha appliance, attach themselves pneumatically
to the enemy's hull. The attacking boat then
retires to a safe distance, paying out at the
same time the electrode wires in connection
with the torpedo, which is then exploded. A
supply of air compressed to a 50th of its nor-
mal volume is kept in a strong reservoir for the
inhalation of the crew maneevering the sub-
aqueous vessel, and is emitted by valves of a
particular construction. Sufficient air is stored
in this way to last 24 hours, and the exhaled
gases are at the same time absorbed by chemi-
cal means.

The Nordenfelt Torpedo Boat. — An-
other very formidable weapon in naval
warfare, and similar to the torpedo boat of M.
Dgevetsky, but differently manceuvered, is the
new submarine vessel of Herr T. Nordenfelt
(the inventor of the gun which bears his name),
which was recently launched at Karlsvik, near
Stockholm . His boat is also cigar-shaped, ox-
posing, when floating on the surface, only a
tortoise like deck with a copula — of glass, we
suppose — just large enough to hold the head of
the commander. Her dimensions are : Length,
64 feet ; height in engine room, 7% f"eet ;
whilst the engines of 100-horse power will, it
has been calculated, propel her for short dis-
tances at a speed of 15 knots, and, when under
water, at a speed of 12 to 13 miles an hour.
The weight of the vessel, with machinery,
coals and full equipment, is 60 tons. When at-
tacking an enemy, the boat approaches to
within striking range, descends a foot under
the surface, and by the course determined be-
fore she descends, and by instruments indica-
ting exactly how far she has proceeded, and to
what depth she has gone, she may approach
near enough to catch the shadow of the vessel
intended to be destroyed, when the torpedoes
are fired at the vessel's bottom. When under
water, the boat is fully protected against fire,
and when on a level with the surface, the cu-
pola— 18 inches in height — alone offers a tar-
get, almost indistinguishable among the waves,
even at short distances. She will be armed
with two fish torpedoes, propelled by com-
pressed air, and also fitted with two rocket tor-
pedoes for defence or attack at short distances.
She is likewise provided with a crane by which
the water ballast in the vessel can be quickly
shifted, when she is not in motion, or if the
automatic apparatus should get out of order.
She is managed by three men, who can without
difficulty spend several hours under water, and
who are to this end provided with air bags at-
tached to the back which supply air through
an indiarubber feeder. The greatest safety for
the crew consists, however, in the circumstance
that the vessel floats on the surface until the
machinery for sinking her and that for keeping
her under water commences working ; and
consequently should part of her machinery be-

VAN NOSTRAND'S ENGINEERING MAGAZINE.

come damaged or cease working, she will at
once shoot up to the surface, an aclion which
can be further accelerated by the discharge in
a couple of minutes of the entire water ballast
of six tons. She is also constructed with four
water-tight compartments, which will prevent
her from sinking before reaching the surface at
all events, thus giving the crew, provided with
life-saving apparatus, an opportunity of escap-
ing. The vessel has been built entirely of soft
Swedish steel % inch to % inch in thickness,
and she is therefore stronger than the ordinary
torpedo boat, which generally has but i^-mch.
plates. Experiments will be made at Stock-
holm shortly, when every precaution will be
taken until her thorough safety has been ascer-
tained. The first trial of descending under
water is to be made in a dock, whilst the crew,
provided with diving costumes, will be in com-
munication with the shore by telephone. The
vessel has, we understand, been built at the ex-
pense of Herr Nordenfelt. For several years
attempts have been made in different countries
to construct such marine war vessels, but the
greatest difficulty encountered appears to have
been quickly to control the movements of the
vessel, and also to keep the men, without dan-
ger, under water for any length of time. The
first of these problems appears to have been
successfully solved in this vessel, as she pos-
sesses a horizontal as well as vertical steering
apparatus, the latter being automatic, so that
the vessel's equilibrium in water is fully con-
trolled by hydraulic machinery.

RAILWAY NOTES.

GROWTH OF THE AMERICAN RAILWAY
System. — The growth of the Railway
system of the United States is one of the most
remarkable items in the entire field of indus-
trial statistics. The 8th of October, 1829, may
be called the birthday of the railway system,
as having been the day on which the locomo-
tive trials were commenced at Rain Hill, on the
Liverpool and Manchester railway. The earli-
est year for which we have official returns of
the length of English railways is 1854, at the
close of which 8,053 miles of line had been
completed in the United Kingdom. In 1830
twenty-three miles of railway were open in the
United States. By the end of 1840, 2 818 miles
were open. In 1850 the length rose to 9,021.
In 1854 it was a little more than double the
length of the English lines, being 16,720 miles.
By 1860 the aggregate rose to 30,635 miles
against 10,433 in the United Kingdom. In
1870 the respective lengths were 52,914 and
15,537, and at the end of 1879, 82,223, and
17,696 miles respectively. The total length of
the railroads of the United States at the close
of 1880, including some lines which do not re-
port their earnings, was 93,671 miles.

It thus appears that if we compare the
growth of the railroad system since 1854 in the
United Kingdom and in the United States,
there has been a steady increase in the former
at about the rate of 3 per cent., and in the
latter at about that of 4| per cent, per annum.
But when we consider, not length of line alone,

but length and cost together, the contrast is
more remarkable. The lowest cost per mile of
an average English railway is that shown by
the returns for 1866, in which year the cost per
mile of line open w as £32,840. From that date
the cost of the railways of the United Kingdom
has steadily increased, till, in 1880, they have
cost £40,613 per mile open. The American
railways, on the contrary, have decreased their
costliness, the average cost of a mile open in
1871 being nearly £12,000, and in 1880 only
about £11,600. The total capital returned as
expended in 1880 was £979,500, 000 in the United
States, and £,802,000,000 in the United King-
dom. The average gross earnings of the
American lines was £1,460 per mile, of which
41.4 per cent, was net revenue. The United
Kingdom lines averaged nearly £3,700 per mile
of gross earnings, of which between 48 and
49 per cent, was net revenue. Thus the Ameri-
can lines cleared a dividend all round of 5.2
percent., against 4.04 per cent, on the English
lines.

The total length of railways in the world
at the commencement of 1880 was calculated
at :

Miles.

Europe 102,593

Asia 8,983

Africa 3,024

America 100,867

Australia 4,338

Total.. 219,805

BOOK NOTICES.
publications received.

Scientific Proceedings of the Ohio Me-
chanics' Institute.

Abstracts of the Proceedings of the
Society of Arts.— Massachusetts In-
stitute of Technology, 1879-1880 and 1880-
1881.

beport to the new york senate on
the Feasibility of Underground
Telegraphy in Cities.

The Edison Electric Light Meter.— By
Francis Jehl.

REPORT ON THE CONSTRUCTION OF TlLLA-
mook Rock Light Station. — By Lieut.
Col. G. L. Gillespie.

Professional Papers of the Corps of
Royal Engineers.— Vol. 6. London.
Edward Stanhope.

Among the papers are the following:

The Artillery Defence of a Fortress.

Development of Field Artillery.

Modern Rifles.

The Fortifications of Monroe.

Fortified Camps.

All of which are treated with that scientific
precision and elaborate fullness for which the
contributions to this journal are justly recog-
onized.

BOOK NOTICES.

s:>

TRANSACTIONS OP THK AmkKICAN InSTI
tute OF Mining Em;im:i:i;s. Advance
sheets.

ontiii.v Weather Review for April.
Washington: Government Printing

Otlice.

Report of Boabd of State Engineers
to the Governor of Louisiana.

Report of Third Meeting of the Micht
\ VssoCIATION OF SURVEYORS AND

Civil Engineers.

MET Al.l.l KCIE PAH AjUfENGAUD AlNE. —
Paris: Librairie Technologique. Price
$5.25.

This is one of a series of "Manuals." The
present issue is devoted to brief descriptions of
recent improvements in the manufacture of
cast iron, wrought iron, and steel. The de-
scriptions being "abridged from the patent re-
ports, arc presented in chronological order
down to the close of 1880.

The Eddystone Light Houses (New and
Old.)— By E. Price Edwards. London:
Bimpkins, Marshall & Co. Price 60 cents.

This is chiefly an abridgement of Smeaton's
own account of the construction of the light
house which made him famous.

It is an interesting bit of history and related

a charming manner.

An account is also given of the newer struc-
ture, only just completed, together with a few
illustrations of both the new and old light
houses.

Petit Vocabulaire Raisonne de Magne-
tisme et DElectricite. — Par A. Sa-
bourain. Paris: Journal d'Electricitc. Price
50 cents.

This is a small pocket dictionary of scientific
terms used in describing magnetic and electric
apparatus or phenomena.

Short descriptions are given of machines or
parts of machines that are kn'own by special
names.

Cocrs de Reproduction Industrielles. —
Par Prof. Leon Vidal. Paris: Dele-
grave. Price $3.50.

The different processes of picture printing
are fully described and beautifully illustrated
in this little hand book of 490 pages. Many of
these new kinds of pictorial illustrations are
called, by the untechnical, photolithogra/pMe
pictures, thereby grouping methods of manu-
facture which are quite unlike.

The details of many of the new operations
are so fully given that the treatise is practically
an instruction book for the amateur.

Egyptian Obelisks— By Henry II. Gor-
ringe, Lieut. Com., U. S. N. New
York: Published by the Author. Price $15.00.
This fine large quarto presents in separate
chapters the following interesting topics :

Chap. I.— Removal of the Alexandrian Obe-
lisk, " Cleopatra's Needle," to New York.

Chap. II. — The Archaeology of the New York
Obelisk.

Chap. III. — Removal of the Luxor Obelisk
to Paris.

Chap. IV. — Removal of the Fallen Obelisk
of Alexandria to London.

Chap. V. — Re-erection of the Vaticau Obe-
lisk.

Chap. VI.— Record of all Egyptian Obelisk-.

Chap. Yll. — Notes on the Ancient, methods
of Quarrying, Transporting, and Erecting Obe-
lisks.

Chap. YIH. — Analysis of the Materials and
Metals found with the Obelisk at Alexandria.

The first chapter will be read with interest
and pride by American engineers, while the
untechnical reader will also find it an intensely
interesting narrative.

The 2d, Gth, and 7th chapters are replete
with historical information, while the 3d, 4th,
5th, and 8th, although of less interest to gen-
eral readers, are necessary to a complete treat-
ment of the subject.

There are 45 illustrations, mostly photo-en-
gravings and artotypes.

Commander Gorringe deserves the patronage
of an extensive sale of the book, and all buy-
ers will surely get the full value of their out-
lay.

Knight's New Mechanical Dictionary.
—By Edward H. Knight, LL.D. Bos-
ton: Houghton, Mifflin & Co.

Since the completion of "Knight's Ameri-
can Mechanical Dictionary," in 1877, the prog-
ress made in the development of the mechanic
arts is unprecedented in the history of the
world. Not only in such striking and wonder-
ful achievements as relate to the telephone,
phonograph, and electric light, toward which
popular attention is naturally drawn, but in
every department of applied mechanics, there
has been developed a fertility of resource in the
adaptation of means to ends quite as marvel-
ous and equally important in practical results.
Achievement has outrun the most sanguine ex-
pectation, and with such rapidity that even the
most recent records are found to be very de-
ficient in supplying the special information '
most desired.

' The hearty approval which "Knight's Ameri-
can Mechanical Dictionary " has received in
all parts of the world has encouraged the pub-
lishers to issue an entirely new volume, thus
continuing the record from the date at which
the former work went to press, but carefully
avoiding repetition, and aiming to furnish not
only a satisfactory supplement to the original
work, but a book which shall have an indi-
vidual and separate value as a complete record
of half a decade in the history of invention.
From this fact it is evident that this volume
forms an indispensable supplement to all
works of reference upon mechanics now ex-
tant, as none of them cover the period men-
tioned .

The same method has been adopted in deal-
ing with the subject matter in both works.
First, each article appears in its proper al-
phabetical place, thus fulfilling the function
of a Dictionary, in affording direct response
to inquiry. Second, the items of informa-
tion thus distributed throughout the work

VAN NOSTRAND'S ENGINEERING MAGAZINE.

are classified in Special Indexes of the Art,
Profession, or manufacture to which they
pertain. The book thus fulfills the function
of a Cyclopaedia, which is a collection of
treatises.

The value of a work of reference depends
largely upon its Index. When one has a ques-
tion to ask of an ordinary Cyclopaedia it is fre-
quently very difficult to determine under which
title or heading to look.

The author has invented a system of what
he terms "Specific Indexes," by the use of
which the inquirer is guided straight to the
information he is in quest of even though
he be entirely ignorant of the name of a
thing, and have but the most vague and gen-
eral "notion of its use. This is accomplished
by grouping under the general title of each
Science, Art, Trade, or Profession a list or
"Specific Index" of every article in the
book bearing any relation to the subject in
question. The titles of these Indexes are in
turn grouped at the beginning of the book,
so that by a glance one may determine which
clew to follow.

Besides the use above mentioned, these Spe-
cific Indexes afford the reader an excellent op-
portunity for investigating thoroughly all
that pertains directly or indirectly to an j
special subject, by using the Index under the
title of that subject as a sort of head-center,
and following out its various branches through
all their ramifications.

Special attention is called to a new and valu-
able feature in the work, by means of which
exhaustive information on any subject is placed
within easy reach; The author has made a
complete Index to technical literature covering
a period of five years, and embracing all En-
glish and American technical journals published
from 1876 to 1880 inclusive. Under title of
each subject may be found a complete list of
every article which has appeared, during this
period, in the columns of these periodicals and
as every subject of importance has been thor-
oughly discussed therein, it is evident that the
whole range of recent investigation is thus
placed at easy command.

A Treatise on Rivers and Canals, Re-
lating to the Control and Improve-
ment of Rivers, and the Design, Con-
struction, and Development op Canals.
By L. F. V. Harcourt, C. E. Oxford : The
Clarendon Press. 1883.

♦ "Rivers and Canals," so-called in the short
title on the back and on the first page, forms
a useful contribution to a class of literature
which is assuming considerable importance.
We mean a class containing books of a compre-
hensive but elementary nature, the true area
for the utility of which lies in those wide fields
open to the engineer in the Colonies, of which
we heard something the other day at the an-
nual dinner of the Institution of Civil En-
gineers. Far away from cities, professional
library, or senior adviser of experience to con-
sult, the young engineer in India or Australia
will find in this volume a very useful hand-
book. The object of the writer, has been, he
tells us, to "present, in a simple and concise

form, descriptions of the principal and most
recent works on rivers and canals, and the
principles on which they are based." In the
book, however, this order is reversed. Mr.
Vernon Harcourt first treats of the meteoro-
logical and hydraulic phenomena of rivers, of
the measurement of river discharge, of the
early and later stages of river navigation, and
of the construction and supply of canals. He
then enters into the practical questions of
dredging-machines and aopliances, of facine
work, piles and coffer-dams; of foundations,
of the works for affording a passage from one
water level to another, of weirs, and of various
works on rivers and canals. This part of the
volume is clear and concise, dealing fairly and
appropriately with the subject, and leaves
little to desire except such a distinct reference
to the authorities relied on as might be avail-
able to the student who has access to a library.
Thus the expression, " it is necessary, accord-
ing to Professor Rankine," (p. 41), and "is
estimated by Professor Rankine," rather stimu-
late than satisfy the curiosity to see what are
the actual words of that eminent writer; es-
pecially as to such an allowance as a- loss of 2
inches of water per day over the whole sur-
face of a canal

Ten chapters are occupied with the foremen -
tioned subjects. The eleventh chapter is a
brief, hasty, and inadequate performance, in
no way up to the level of the rest of the book.
It is headed. " History of Inland Canals." The
facts stated are few, and the statements are
not always accurate. Thus we find, "There
are 300 miles of canals in Ireland," the fact,
being that there are 392 miles of canals and
river navigation in possession of companies,
133 miles under the control of local masters,
and 227 miles under Public Works Commis-
sioners— in all, 752 miles, instead of 300.

The inadequate mode of dealing with this
part of the subject is the more to be regretted
from the fact that where there is one man who
wishes to be instructed as to the method of
making a canal, there are hundreds who are
anxious to know what canals are in existence,
what canals are in process of construction, and
at what cost traffic can be conveyed on canals,
as compared to railways. It is hardly too
much to say that this is the industrial question
of the day. As such, at all events, it is re-
garded to a great extent by manufacturers,
and discussed by Chambers of Commerce
throughout England. To treat it with any ap-
proach to accuracy would require not a chap-
ter, but a volume. Still, something useful
might have been said in a chapter, and, al)ove
all, what little was said, ought to have been
correct.

In the next chapter, on Ship Canals, Mr.
Vernon Harcourt does more justice to his sub-
ject and to himself. The short notice of the
Languedoc Canal has all the more interest from
the fact that the construction of a new Ship
Canal from the Mediterranean to the Bay of
Biscay is at this, very moment under discussion
in the French Cabinet.

There is a good account of the Amsterdam
Ship Canal, abstracted, as are most of the fol-
lowing descriptions, from the excellent author-

MISCELLANEOUS.

ity of the Minutes of Proceedings of the Insti-
tution of Civil Engineers. The account of the
Fen Rivers, chiefly taken from Mr. Wheeler's

•• History of the Fens," is also clear, though
brief. Three chapters on the improvement of

tidal rivers will he read with interest and ad-
vantage. The accounts of theLufey, the Yare,

the Clyde, the Tyne, and the 'Fees are taken
from the "Minnies.'' There is a want of ref-
erences as to the other instances cited, hut the
work is done clearly and well, and Mr. Vernon
Ilarcourt shows himself a careful abstractor.
But the cases which he selects must be re-
garded rather in the light of vignette illustra-
tions, so to speak, of the various methods
adopted by river engineers, than as a general
description of river and canal communication.
So far, indeed, is the author from attempting
such a work on navigation as is suppled, with
reference to France, by M. Felix Lucas, in his
"Etude Historique et Statisque sur les Voies
de Communication de la France," that he de-
scribes the future works of the Panama Canal
with as much gravity as the actual engineering
of other parts of the world. And he has done
so while citing on one page the unqualifiable
sertion of M. deLesseps, " that the construc-
tion of a Ship Canal across the Isthmus of
Panama presents fewer difficulties than the
Suez Canal," while he tells us in another page

solid matter ;uid tiny air bubbles, which were
seen to be in rapid rotation. Mr. Stanley illus-
trated his theory with a number of corroborative
experiments with pipes of different form9.

KSTKl ( TION OF ('AHIU)N ELECTRODES BY

continued Electrolysis. — Bartoli first
observed that the quantity of gas generated
during the electrolysis of water at the positive
pole was comparatively too small, that is, 1<
than half the volume of gas collecting at the
negative pole, when this positive pole consisted
of carbon. The loss could be explained by a
combination of the delivered oxygen and the
carbon. In connection with M. Papasogli, then,
M. Bartoli further studied the matter, princi-
pally to ascertain what organic bodies would
result under these circumstances. As such they
determined mellitic and hydro-mellitic acids.
Their experiments are, however, not less in-
structive from another point of view, as they
show that the use of carbon as a positive elec-
trode finally ends in the total destruction of the
solid carbon. A fine powder soon collects at
the bottom of the voltameter, and the liquid
itself becomes more and more colored, not from
sensibly suspended particles of carbon, as might
be presumed, because repeated filtering and
keeping the liquid undisturbed for months does
not produce any change in the color. Distilled
water as well as diluted solution of nitric, sul-

that for the latter " no constructive works of phuric, acetic, oxalic acids of potash, soda, and
any magnitude had to be executed/' Con- J some carbonates, were tested with pretty simi

sidering that the Culebra cutting of eight miles
long varies from a depth of 100 feet to that of
300 feet, through a pass of the Cordillera, the
idea of what constitutes engineering difficulties
is not quite distinct.

The plates, which form a separate volume,
are clear and good. There are twenty-one
plates, all folded, and twenty woodcuts in the
text. The work can be safely commended to
the student, who will find brought together in
its pages much for which he would have to
search widely in order to collect it for himself.

MISCELLANEOUS.

The Flow of Liquids in Pipes. — At the
recent meeting of the Physical Society, Mr.
W. F. Stanley read a paper on the flow of
liquids in pipes, and showed that liquids move
by rolling contact upon or past the resistant
surfaces of the pipe, and not by sliding, gliding
or shearing action, as has been generally as-
sumed. The difficulty in carrying out his ex-
periments lay in the fact that when a liquid
flows through a pipe the friction of the pipe
prevents the free motion of the rolling particles.
For this reason with circular pipes the evidence
of rolling contact is of a very complex char-
acter, and particles of solid matter, for example,
descending in glass pipes take a spiral or zig-
zag path very difficult to follow. Evidence of
surface rotation was, however, found in the
descent of a liquid cylinder or column of dense
mastic varnish through a tall narrow beaker
from a glass funnel. The length of the descent
was about 18 in., and the width of the column,
4 in. It carried down with it small particles of

lar effects. Of the three sorts of carbon em-
ployed, graphite, gas carbon and charcoal, the
two latter are used somewhat quicker. One
piece of carbon electrode was totally destroyed
in 29 days, with 100 Bunsen elements acting
for four days, 40 elements for five, and 20 ele-
ments for 20 days. Carbon may, on the other
hand, be used as a negative electrode without
any risk, a distinct proof that we have to deal
with an oxidation process.

The following subjects are announced by
the Belgian Academy for prize competi-
tion : In mathematical and physical science :
Establish, by new experiments, the theory of
reactions of bodies in the so called nascent
state. Prove the accuracy or falsity of the fol-
lowing proposition by Fermat : To decompose
a cube into two other cubes, a fourth power,
and generally any power into two powers of
the same name, above the second power, is im-
possible. New spectroscopic researches re-
quired as to whether, especially, the sun does
or does not contain the essential constituent
principles of organic compounds. Extend,
as much as possible, the theories of points and
straight lines of Steiner, Kirkman, Cayley, Sal-
mon, Hesse and Bauer, to the properties which
are, for superior plane curves, for surfaces, and
for skew curves, the analogues of theorems of
Pascal and Brianchon. In natural sciences :
New researches required on germination of
seeds, especially on assimilation of nutritive
stores by the embryos. New researches re-
quired on development of Trematodes, from
the histogenic and organogenic points of
view. New stratigraphical, lithological, and
palseontological researches required, to fix the
arrangement or the order of succession of

VAN nostrand's engineering magazine.

layers of the formation called Ardennais by
Dumont, and at present considered a Cam-
brian. Medals valued at 800 francs will be
given as prizes in the first division; medals
of 600 francs in the second. Memoirs may
be written in French, Dutch, or Latin, and
should be sent (in the usual form) to the Sec-
retary, before August 1, 1883.— Nature:

A simple new thermometer, said to be very
sensitive, has been described {Jour, de
Phys.. April) by Mr. Michelson. It depends
on the expansion of hardened caoutchouc by
heat. A very thin strip of the substance is at-
tached to a similar strip of copper. The lower
end of the double strip is fixed, and the other
has attached to it a fine glass fiber bent at a
right angle, through which, as the strip bends
under heat, motion is imparted to a very light
silvered-glass mirror, hung by a cocoon fiber.
The displacement of the mirror is observed
with a telescope and reflected scale, or by the
movement of a spot of light. To avoid sudden
changes of temperature, the double strip is in-
closed in a metallic case having a slit opposite
the strip. In a modification, which the author
has not yet tried, the strip is reversed, and the
lower end enters a highly resistant liquid, in
which it faces a metallic point; the two serve
as electrodes, connected with a galvanometer
and a Wheat stone bridge. — Nature.

By authorization ©f the Russian Minister of
Public Instruction, the Imperial Univer-
sity of St. Petersburgh is about to found an as-
tronomical observatory, which will be of small
size conformably to its principal object, which
is to facilitate the studies of those who are en-
gaged in the University curriculum. The prin-
cipal pieces forming the materiel will be two re-
fractors, with Merz object glasses, one 6 inches
aperture, the other 4 inches, parallactic mount-
ing and clockwork motion, several transport-
able astrouomical instruments, and an astro-
nomical clock, with some other secondary in-
struments.

At a recent meeting of the Seismological
Society of Japan, Prof. Milne read a
paper on the " Distribution of Seismic Activity
in Japan." This paper was to a great extent
founded on communications received from al-
most all parts of Japan in answer to inquiries
respecting the occurrence of earthquakes in
various districts. As the result of these in-
quiries, during the past two years, Mr. Milne
had received, in addition to general opinions
respecting the seismic activity of various dis-
tricts, a very large number of actual records.
Commencing in the north and proceeding to the
south, notes and catalogues of earthquake in-
tensity for the whole country were given. Thus
for Hakodate, in Yezo, from 1876 to 1880, a
catalogue of forty-two earthquakes was given.
By comparing this catalogue with that of Sap-
poro, in the same island, it was seen that ten at
least of the Hakodate shocks had been felt at
Sapporo, eighty miles to the northeast ; and
similarly it was* shown that seven of the shocks
were felt at Tokio, five hundred miles to the

south. From the times at which a shock was
felt in different localities, its intensity and the
like, origins tor certain shocks were roughly
computed. The district around Tokio is of
course that which is being most thoroughly in-
vest] gated ; and as it was only possible to ob-
tain accurate observations as to the time at
which shocks were felt at one or two localities,
and farther, as it was shown that the direction
in which the earth moved at any given point
as indicated by a seismometer did not neces-
sarily indicate the direction from which the
earth waves were advancing, Mr. Milne has
adapted the following simple method as an as-
sistance in tracing earthquakes to their origins.
All important towns within a radius of one
hundred miles from Tokio have been furnished
with bundles of post-caids, one of which is
posted every week stating whether earthquakes
have or have not been felt. In this way, at the
end of last year, Mr. Milne found that the
greater number of the earthquakes which were
felt in Tokio bad only been felt in the towns
to the north of that city, and a short distance
to the south. This fact being established the
barrier of post-cards was continued about two
hundred miles still farther north, with the re-
sult of enclosing, so to speak, the origin of sev-
eral shocks, and tracing others to the seashore.
The latter could no longer be pursued by means
of post-cards, and instrumental observation
alone had to be relied on for the determination
of their origin. These observations, so far as
they have at present gone, show in a remark-
able manner how a large mountain range ab-
sorbs earthquake energy. Thus, it is very sel-
dom that an earthquake traveling from the
north passes beyond the Hakone range of
mountains to the south of Tokio. Earthquakes
having their origin on either side of such a
range rarely travel to the other side, however
large their area of activity on their own side
may be. The whole of Japan has in this way
been divided into districts of varying seismic
activities. By two separate systems of investi-
gation Mr. Milne showed that, if instruments
of ordinary sensitiveness were distributed
throughout Japan there would on the average
be recorded, at the lowest estimate, over 1,200
shocks per year, or about three shocks per day,
which is a number greater than that obtained
by Prof. Hein for the whole world.

Anew dynamo-electric machine, recently
brought before the Belgian Academy by
M. Plucker, has the peculiarity that a solenoid
is substitued for the electro-magnet as an organ
for excitation of the induction currents. ". The
horizontal coils of the solenoid, which is of spe-
cial form, are traversed by the currents pro-
duced by the machine itself. The apparatus
rotated within the solenoid is a wheel with
coils arranged nearly like those of the Gramme
ring. The whole system is enclosed in an iron
armature meant to increase the inductive ac-
tion. M. Plucker states that he replaced the
solenoid with electro-magnets, and the appara-
tus produced the same effect. He seems merely
to claim the advantage of less weight and vol-
ume.

VAN ISTOSTRAND'S

Engineering Magazine.

NO. CLXIV.-AUGUST, 1882-VOL. XXVII.

BASE-LINE APPARATUS.

By H. BREEN, University of Cincinnati.
Contributed to Van Nostrand's Engineering Magazine.

The sources from which information
has been drawn for this paper, are the
reports of geodetical surveys of England,
India, France, the United States, and
several contributions to the American
Philosophical Transactions. Besides
these, Col. A K. Clarke has given a
sketch of the subject in the article en-
titled Geodesy in the Encyclopedia Brit-
tannica, and also a more extended review
in his recent work upon Geodesy. Fur-
ther than these there appears to have
been no treatment of the matter as a
whole, probably because there is greater \
interest attached to the larger fields of \
general geodetical research.

The degree of accuracy with which
angles are measured by such instruments
as those of Wurdemann, Ramsden, and
others, compels a corresponding degree
of precision in the measurement of base
lines. But though an angle may be
easily measured and remeasured until
theoretically and practically a very high
degree of accuracy is attained, the repe-
tition of the measurement of a base line '
requires an outlay of time and money j
that becomes a matter for serious con- '
sideration. The length of a measuring ,
bar being once determined, it is evident
that any error in its supposed length or !
in the method of using it will be re- j
peated as many times as it is used in I
Vol. XXVII.— No. 2—7.

measuring the base, and hence no pains
should be spared to secure the highest
possible degree of exactness in its con-
struction and use. The apparatus should
also be light, portable, and easy of manip-
ulation.

The measuring bar must be of known
length, and its variations from a stand-
ard length must be rigidly determined as
regards their amount and regularity.
In connecting two systems of triangula-
tion the units of length employed in each
must be compared. Hence it is that such
comparisons become of primary impor-
tance, and the first portion of this paper
will be devoted to that subject.

In comparing the length of one bar
with another or with standards of length
the bar is usually placed horizontally.
The manner in which it is supported will
require attention, since the bar will be
deflected by its own weight, and conse-
quently shortened horizontally. The
following is an investigation of the
change in length due to deflection as
given by Clarke, somewhat expanded.
Let a be the length of a rectangular bar

Fig.l

of depth k and width h. Let w be its
weight and d the total extension of the

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

bar due to a load w attached to its lower
extremity when suspended vertically.
Suppose AB to be the bar, supported
horizontally at the points P, P', whose
distances from the center C are b and b'
respectively. If E denote the coefficient
of elasticity, then

w d wa
hk ' a dhk
The moment of resistance to flexure is
EI_E hk\_wa¥
M~ — ~Vl2 ~VMr

in which I represents the moment of in-
ertia and r the radius of curvature at any
point as g. Using rectangular co-or-
dinates, the origin being at C, and the
axis of x passing through the points P
and P', the moment at any point be-
tween C and P' is

wok2 bio ,_, , w 5

and between P' and B is
wak2
VLdr

w/a
'~a\2

■x

(!)•

(2)-

1 d*y
If in (1)-=-t-y be equated to zero and

the equation solved for x the resulting
value of x will be that of the point of in-
flection. Thus,

2 b' + b b' + b

from which it is evident that a real poinl
of inflection is only possible when

S+Wf.

The shortening of the upper fiber will

>b d*y

*f a?*-*-**/"--^*

2 d2y

+\hf % dx+w f

2 d2y

dx2

dd( ,,, d2\

If this extreme fiber is to retain its

a1
original length bb' must equal — , or

b = b'=

is the condition for a bar
2 a/3

supported symmetrically. When, how-
ever, a bar is supported at distances
from one extremity equal to \ and J its
length, as is often the case, the horizon-
tal projection of the upper fiber will be

less than the actual length by — -7-.

Before the discovery of this theorem by
Airy, the British Ordnance Survey found
the error due to deflection by laying a
straight-edge upon the bar and measur-
ing the deflection by inserting a wedge
between the bar and straight-edge. If
the curve of the neutral axis be consid-
ered a circle, the length of the required
chord subtending it is readily calculated
from the deflection.

The effects of flexure may be over-
come in several ways ; as by floating the
bar in mercury^ either loaded with
weights or not ; or by cutting down un-
til the neutral axis is exposed, and mark-
ing the extremities of the measure upon
it. By this latter method any error due
to tension or compression of fibers is ob-
viated, but not that due to curvature.

Standards of length, with which bars
are compared, may be divided into two
general classes: Standards " a bouts,"
in which the ends of the bar are disk-
shaped ; and standards " a traits," in
which the length of the bar is indicated
by lines or dots engraved on the neutral
axis. In the first class an error may
arise, when a microscope is used in mak-
ing the comparisons, by sighting at a
point on the disk which is not at the ex-
tremity of the axis. Clarke has shown
the probable error to be a minimum
when the radius of curvature of each
disk is equal to the length of the bar.

The thermometer with which the tem-
peratures are taken during these compari-
sons must be of superior workmanship,
and more especially is this true of those
which are to serve as standards with
which to compare other thermometers
used in the field or elsewhere. The in
dex and calibration errors must accord-
ingly be determined at intervals in or-
der to discover any changes which the
thermometer may have undergone.
Thermometers may be compared at high
temperatures by immersing them in hot
water and making comparisons as the

BASE-LINE APPARAT! s.

water cools ; but for lower temperatures
it is probable that a somewhat greater
degree of accuracy is obtainable by read-
ings taken when the temperature is
nearly stationary and the thermometers
in a protected place.

The comparison of bars is usually con-
ducted in a structure erected especially
for the purpose. The British Ordnance
Survey building in which this work is
conducted is a room half sunk in the
ground, roofed over with nine inches of
concrete, and having double walls. It is
completely surrounded by an outer
buildiug, and thus the changes of tem-
perature are of the most gradual charac-
ter. Three stone piers built upon deep
brick foundations rise through the floor-
ing, but have no connection with it.
Upon them rest heavy cast-iron blocks
which hold the microscopes in position.
The comparisons are made in the fol-
lowing manner : The bars are each
placed in two rollers in a box, and lev-
eled by means of a vertical movement
imparted to the rollers. One of the bars
is then brought under the micrometers
and readings taken, the temperature be-
ing noted at the same time. The first
bar is then replaced by the second and
the micrometers adjusted and read, then
thrown out of focus, readjusted and
again read. Finally, the first bar is put
under the microscope and observed as
was the second, after which the tempera-
ture is taken.

It is to be noticed that the tempera-
ture of any body as indicated by a ther-
mometer cannot be correct unless the
body either possesses the same specific
heat, absorptive, radiant, and conductive
powers as mercury, or the temperature
is stationary ; and hence all observations
made in the field during the measure-
ment of a base line are subject to an er-
ror of which account should be taken.

The errors of the micrometers and the
personal errors of the observer are also
matters to be considered. In the series
of comparisons made by the Ordnance
Survey between 1831 and 1842, it was
discovered that the stone pillars then
used had sufficient motion to produce an
error. This difficulty has probably since
been overcome.

As illustrating the method by which
bars are reduced to the standard tem-
perature, the following is taken from Tol-

land's Ordnance Survey. Suppose two
bars, A and B, are to be compared.

Let a, a,, av &C, denote the observed
differences of length ;

>/>, mt, ?».,, etc., the differences be-
tween the observed temperatures
of A and 62° Fahrenheit, which
is the standard temperature
adopted ;

n, n., »2, &c, the same differences for
B ; x,y, the rates of expansion of
A and B respectively for each de-
gree Fahrenheit ;

z, the true difference of length of
the bars at 62°.

The observations will then furnish a
series of equations ; as,

a + msr— ny— z=o,
al-\-m1x—nly—z=o,
&c, &c.

By the method of least squares the fol-
lowing normal equations may be formed :

2 am -f- x2m2 —y2mn — z2m = o,

— 2an—x2mn + y2ri2—z2?i=o,

— 2a— x2m + y2n -\-pz=.o,

when p denotes the number of observa-
tions. The most probable values of
j x, y, and z are therefore known.

In the comparisons made by the Coast
! Survey SaxtonVpyrometer is employed
I instead of the micrometers, and it is
| quite certain that the results are there-
: by rendered more trustworthy. This in-
, strument may be briefly described as fol-
\ lows. The bar under inspection is al-
I lowed to expand at one end only, and in
| so doing pushes a sliding rod to which
i is attached a very delicate chain. The
| latter by being unwound communicates
the motion of the rod to a cylinder, caus-
| ing it to revolve together with an at-
; tached mirror. At some distance is
, placed an arc, and to the rear of and
above it a telescope. The mirror re-
flects the graduations of the arc into the
I telescope. A very slight motion of the
; mirror will cause a considerable change
| in the reading of the arc. A full account
of the method in use by the Coast Sur-
vey is contained in the report for 1862,
from which the above description is
, taken.

The Ordnance Survey building above
described is supplied with apparatus for
determining the absolute rates of expan-

VAN NOSTRAND'S ENGINEERING MAGAZINE.

sion of standards. The bars are placed
in tanks, one of which contains ice water
and the other hot water supplied to it by
means of flexible pipes leading to the
supply which is kept without the build-
ing. The tanks are so arranged that
they may be placed under the micro-
scopes fixed upon the piers without re
moving them from the tanks. A com-
plete observation consists in comparing
a bar in the hot tank with another in the
cold tank, and then making a similar
comparison after interchanging the bars
in the tanks.

A very neat arrangement has been
used by the Ordnance Survey to insure
the parallelism of the surfaces of two
bars when brought successively under
the microscopes. It is simply a curved
lever, the short arm of which carries a

abandoned and glass tubes 20 feet in
length were substituted. This measure-
ment was afterwards verified by using a
200 foot chain, constructed by Eamsden,
which was laid in deal coffers supported
by wooden trestles, and stretched by a
weight of 28 pounds.

A great impetus was given geodetical
operations by the determination of the
length of the meter, wich is a ten-
millionth of a quadrant of the earth.
The necessary triangulation for this
purpose was undertaken by the Con-
stituent Assembly of France in 1792.

In 1827 Colby began the trigonomet-
rical survey of Ireland by the measure-
ment of a base near Londonderry, with
an apparatus the fundamental principle
of which was that of compensation as in
the gridiron pendulum. This principle.

hook or point which rests on the bar,
while the longer arm traverses a vertical
scale. It is only necessary after having
leveled the first bar and recorded the
readings of the levers at each of its ex-
tremities, to make the readings of the
levers for the second bar agree with
those of the first by means of the level-
ing screws under the bar. By this ar-
rangement any error due to a want of
parallelism of the surfaces observed, or of
the axis of the microscopes, is wholly
overcome.

The first base lines were measured
with rather crude devices. The rods
used by the expedition of the French
Academy at Tornea, in 1736, were of fir,
each five toises in length. A toise is
about six feet.

The base at Hounslow Heath was first
measured with deal rods terminating in
bell-metal tips ; but the inaccuracy of
these became so apparent that they were

has been employed in the construction of
all the more accurate instruments of
this character in the United States.

Suppose two rods, W and ii, to be
fixed at their centers, o and o'. If at
some temperature they are of equal
length, let that temperature be increased
until ob' expands to ob" , and o'i' to o'i" .
Should a strip of metal be fixed across
the bars in the position b'c, it is evident
that if the strip be so pivoted to the
bars that b'c : i'c : : e& : e^ where e& and ei
represent the respective rates of ex-
pansion of the bars, then the point c will
not vary its distance from o" . Thus, if
a point be similarly fixed at the left-hand
end of the rods its distance from c will
be invariable provided the rates of ex-
pansion are constant, and the rods do
not at any time differ from each other
in temperature. The rates of varia-
tion in temperature will be due to
difference in mass, conductivity, powers

BASE-LINE APPARATUS.

of radiation and absorption, and specific
heat.

It is known that if a bar be heated and
then cooled to its original temperature,
it does not necessarily return to its
original length. The principle of com-
pensation will no doubt be adandoned
in time for the more accurate method of
the Spanish and Algerian surveys, to be
hereafter described. It is doubtful
whether Colby grasped the problem in

closed by a lid, through which a level at-
ched to the brass rod could be viewed.
A vane-sight was screwed to each end of
the box to serve in alignment. The ap-
paratus was supported upon an arrange-
ment technically known as a " camel,'' at
J and j its length. These devices pro-
vided for a horizontal as well as a verti-
cal motion, and were in short the means
of aligning and leveling the box. The
trestles used by Colby were of wood, and

i — 70'

/
/

Fig.3

its entirety, though he adopted such
means as would correct the errors due
to the factors above enumerated. He
chose iron and brass as his materials ;
the former he decided to make the
compensating material. In order that
they may be of the same tempera-
ture, rods should acquire equal in-
crements of temperature in the same
time — that is, their absorbtive powers
should be equal. This may be ac-
complished by properly adjusting the
character and relative area of the
surfaces of the rods. Colby coated the
iron bar with a mixture of varnish and
lampblack, gradually removing it from
portions of the surface until, by experi-
ment, the required adjustment was
effected. This coating was then re-
moved and a new one applied contain-
ing the requisite quantity of lampblack.
The Colby bars rested upon rollers at
i and £ their length, and were connected
at their centers by a pair of cylinders.
The tongue was of steel, carrying a sil-
ver pin at the outer extremity, upon
which the compensated dot was placed.
The whole apparatus was inclosed in a
wooden box from which nozzles pro-
jected at each end to serve as protectors
for the tongues. A lid in each nozzle
permitted the observation of each dot
by means of a microscope. Pins passed
through the cylinders connecting the
bars, and were inserted in the sides of
the box to prevent lateral motion. In
the top of the box was an aperture,

not of elegant design, though very sub-
stantial. A plate firmly screwed to the
end of each box served as a support
for a three-armed grooved stand upon
which was placed the compensating
microscope. Each box with its plates
weighed 136 pounds.

The compensating microscope con-
sisted of three microscopes. Two were
held in position at such a distance as to
keep their foci six inches apart by means
of arms projecting horizontally from col-
lars which encircled the central micro-
scope near its upper and lower ends.
These bars, being made of brass and
iron, acted as compensators. The outer

o n n

Fig.4

microscopes had a focal length of two
inches. The central or telescopic micro-
scope had its focal distance varied by
means of a screw projecting horizontally.
The three were inclosed in a rectangular
box which was supported upon a cylin-
der surrounding the central microscope.

VAN NOSTRAND'S ENGINEERING MAGAZINE.

This cylinder was attached to a plate
which could be put in motion horizon-
tally by means of tangent screws. On
opposite sides of the rectangular box
were attached a level and a telescope for
alignment. The weight of the micro-
scope was 5 pounds.

The telescopic microscope transferred
the terminal point vertically to an ar-
rangement known as a "point carrier,"
which served to fix the end of a day's
work, or answered some similar purpose.
It consisted of a heavy iron plate which
carried a disk, or of an upright cylinder
whose upper surface formed the disk.
Upon this surface was engraved the line
or dot which indicated the extremity of
the measured distance, the disk being
movable in a groove of the plate.

Colby's apparatus is still used in the
English surveys, but does not appear
to give entire satisfaction. In the
measurements at Cape Comorin, during
the triangulation of India, thermometers
were used, and the base, which is
nearly north and south, was divided into
four segments, each of which was meas-
ured four times — twice with the brass

bar to the east, and twice with the iron

/ •

bar east.

In 1816 the Russian government
undertook the trigonometrical survey of
the provinces of Lithunia and Livonia.
The latter survey was accomplished
under the direction of the elder Struve ;
the former, by Tenner. The character
of the country was so favorable that it
was decided to take advantage of it in
measuring the great arc, which extends
from Ismail, near the mouth of the Dan-
ube, to the northern boundary of
Sweden, a distance of 1,800 miles, and
corresponding to 25° 20' of arc. The
task was completed in thirty-six years.
It required the measurement of 10
bases ; the determination of latitude at
13 points ; and the location of 275 prin-
cipal stations.

Struve invented a base-line apparatus,
which may be briefly described as fol-
lows. It consists of a single bar of iron
two toises long, terminated at one ex-
tremity by a small cylinder, while to the
other extremity is affixed a lever, known
as the lever of contact. The end of the
short arm of this lever is spherical in
form ; the longer carries an index moving
in front of a graduated arc attached to

the bar. The reading of the arc indi-
cates the length of the bar as found by
observation. The lever, being placed in
contact with the forward bar, is main-
tained in position by a spring attached

Fig.5

to the lever. A pair of thermometers
lying in the bar indicate its temperature.
The bar is wrapped with cotton and cloth
to guard against rapid changes of tem-
perature.

In the geodetical operations of De-
lambre, executed under the direction of
the French Academy, Borda's apparatus
was employed. Each rod consisted of a
platinum strip two toises long, upon
which lay a copper strip, free to expand
in one direction only. The copper strip
being somewhat the shorter, served as a
measurer of the platinum strip. In prac-
tice this was effected by means of a scale
engraved upon the copper, which was
read by a vernier on the platinum. From
this reading the length of the platinum
strip was calculated. At the extremity
of the platinum strip was a smaller piece
of the same material, sliding in a groove
cut in the larger strip, and having *upon
it a vernier, which served to measure the
distance between successive bars. Both
verniers were read by microscopes.
The inclination of the rod was read from
a vertical arc of two feet radius, whose
error was eliminated by readings taken
in reverse position.

Bessel's apparatus was similar to Bor-
da's, with the exception of the device for
measuring the intervals, and the substi-
tution of iron and zinc for platinmu and

HASE-LINE APPARATUS.

.copper The intervals are measured by a tained,and the length of the base may be

represented by an equation of the form

scale cut upon a glass wedge, which is
introduced between the bars. The zinc
strip carries at each end a horizontal
knife edge, and the small strip of iron
has two vertical knife-edges. The dis-
tance between the inner of these latter j It may be seen by a comparison that four
and the horizontal knife-edge of the i rods is the least number by means of

ii% + avl + /?u9 + yv3 + 6vA 4- a'?\ +

zz.

Fig.6

zinc is measured by inserting the wedge.
Let i denote the actual distance meas-
ured by the wedge ; then if lx and /2 de-
note the length of the strips at the time
i is observed, we shall have :

i—z-\-7n (x—y);

using the notation previously adopted.
If l\ and l\ are the lengths at 62°, ob-
tained by comparison with a standard ;

l\x~l\y

h =

x-y

iy
x-y"

which may be taken to be the length of
the iron piece at any observation.

Bessel used four rods in his measure-
ments, each similar to that above de-
scribed. Represent the lengths of the
iron pieces by L,, L.2, L3, and L4. Let
there be some length s, obtained by a
comparison of one of the bars with a
standard, and let v,, v3, y3, v4 denote
small variations of length of the bars
from 5, so that v^ + v^+ y3 + u4=o.

Also let tp t^ tz, t4 be the observed
temperatures, and r,, r9, r3, i\ rates of ex-
pansion. Then

Li = 5 + yi + ^v

It4=8 + v4 + t4r4.

From the eight equations obtained by
a comparison of the rods inter se, and
the condition v, + v2 + u3 + ?;4 = o, the val-

ues of r„ r2, r3,

r4, and w„

v9, i\, vK are ob-

which the unkown quantities can be de-
termined.

In marking the close of a day's work
Struve projected the terminal point_on a
cube sliding in a groove cut in andiron
plate, by means of a transit set up at
right angles to the line of the base.
Bessel used a plummet to transfer verti-
cally. In the Belgian bases, where Bes-
sel's apparatus was used, a plate carrying
a horizontal knife- edge at the rear end
and a vertical one at the advanced end,
served to indicate the end and beginning
of operations, the distance between the
knife-edges being part of the base. This
plate moved in a groove cut in its sup-
port and could be clamped. Its iron
support was built in with brickwork at
some point previously determined upon.

The instruments mentioned above are,
with one exception, those with which the
principal European bases have been
measured.

In this country the first base used in
triangulation was measured in 1830 by
Simeon Borden, Superintendent of the
Massachusetts State Survey. His appa-
ratus was constructed upon the compen-
sation principle. Borden made his own
apparatus and measured with it a base
near Northampton, of 7.4 miles, with a
probable error of 0.237 inches. The ap-
i paratus was contained in a tin tube, 50
! feet in length and 8^ inches in diameter,
I tapering toward the extremities. The
i tube was closed at its ends by cast-iron

VAN NOSTKAND'S ENGINEERING MAGAZINE.

plates through which the rods projected.
These latter were of brass and steel, f
inch in diameter, and rested upon 19
supports. Each rod consisted of four
segments which were united by means of
mortises held in a " coupling-box." The
rods were kept at a constant tension by
a spring at one end of the tube which
was compressed between diaphragms, the
inner one being fixed and the outer
pressed against an iron nut screwed upon
a rod. This rod in turn pressed an arm
attached to the brass and steel rods at
equal distances from the iron rod. The
couplings were fastened by movable
joints to the arms or indices at each end,
and the index not connected with the
iron tension rod is made to stand at a
constant angle with the axis of the tube
by means of a stirrup-like arrangement
screwed to this index and to the iron
plate closing the tube. The compensated
point was adjusted by means of two silver
indices, one attached near the end of the
arm and the other to the head of a clamp
which could be regulated. The micro-
scopes were compound, consisting of a
single object-glass and an eye-picee of
two lenses. They were held in frames
supported by a trestle. • The whole ar-
rangement was evidently an adaptation
of Colby's apparatus. Borden secured
uniform absorption in the usual manner,
but for some reason appears to have at-
tempted no further adjustment of the
rods for temperature.

The first base measured by the Coast
Survey was under the direction of F. R.
Hassler, the first superintendent, and is
known as the Fire Island Base. The ap-
paratus was of his own designing, and
consisted of four two-meter bars inclosed
in a wooden box. A single microscope
read the index on successive bars. The
base was 8f miles, and the probable
error as given in the Coast Survey Re-
port for 1865 is shown to be ± 0.0585 m.
The apparatus now used by the Coast
Survey is the invention of Bache, and in
its construction involves the principles
employed by Colby, Struve, and Borda,
A very readable description of the instru-
ment is given in Van Nostrand's Maga-
zine of 1875. Its general design may be
sketched as follows : Two bars, each
about six meters long, are contained
within a double tube, coated white with-
out, so that changes of temperature are

very gradual and the annoyance arising
from the use of tents is avoided. The *
bars are of iron and brass firmly united
at one extremity. The iron bar is placed
above and runs on the brass bar by
means of stirrups and rollers. The lower
or brass bar expands on rollers attached
to the framework of the tube. At the
free end of the bars is a curved lever
pivoted to the lower bar and carrying
upon its inner surface a knife-edge which
is in contact with a steel plane attached
to the inner bar. Fastened to the upper
surface of the iron bar is a frame, through
which slides a rod. The compensation
lever passes into a collar carried by this
rod, and its point abuts against one of
the faces of the collar. A spring at-
tached to the rod and frame in which it
slides serves to press the lever back at a
constant pressure, and consequently to
cause a constant pressure between the
knife-edge and the steel plane carried by
the iron bar. The sliding rod has at its
outer extremity an agate plane which is
thus kept at a constant distance from the
fixed extremities of the bars. The ex-
tremity of the apparatus just described
is termed the compensation end.

The most important parts of the " sec-
tor end " may be described as follows.
A sliding rod projects, which, coming in
contact with the agate plane of the com-
pensation end causes a pressure. It is
necessary that this pressure of contact
should be constant, and this has been
secured by means of an arm pivoted to
the lower bar, and against which the
sliding rod abuts. At its upper end the
arm presses a short tail which drops from
a spirit level mounted on trunnions, so
that it always requires the same force to
bring the bubble to the center. This
level is fixed to the sector proper, which
is an arm, carrying at its inner extremity
a vernier which reads a fixed vertical
arc, whose zero corresponds to. the cen-
tral position of the bubble of a second
spirit level attached to the sector. The
axis of the level being parallel to the
axes of the bars, the arc reading indi-
cates the inclination of the apparatus to
the horizon, from which the length of the
horizontal distance corresponding to the
measured length is readily deduced.
The trestles which support the apparatus
are of careful design, and by means of
the horizontal screws and of a rack-and-

BASE-LINE APPARATUS.

pinion movement of the legs considerable
latitude is attained. In measuring a
base, wooden frames are approximately

adjusted in advance for the trestles to be
placed upon.

In the construction of the bars, Bache
not only used the device of Colby for in-

suring equal temperatures of the rods,
but made allowance for different con-
ducting powers, and adjusted their

masses inversely as their specific heats.
There appears to be a permanent change
of length of the bars which is probably
irremediable. It is the result of changes
of temperature.

The measuring bars are compared
with the standards of length both before
and after the completion of a day's work.
For this purpose a modified form of
Saxton's pyrometer is used, in which the
bar is made to abut against a horizontal
arm which projects from the vertical axis
of the mirror. The first base measured
with this form of apparatus was at Dau-
phine Island, near Mobile, in 1847. The
base was seven miles in length, and re-
quired seventeen days for its measure-
ment. In the rapidity with which the
operations are executed Bache's appa-
tus is superior to any other, 1.06 miles
having been measured in a single day
The tests to which it has been put cer-
tainly show it to be superior to all except
the base line apparatus of Porro, which
will now be described.

This method differs considerably from
those before employed, for but a single
bar is used which serves to measure the
distance between successive microscopes
placed upon fixed stands. The bar con-
sists of two cylindrical rods, united as in
Colby's apparatus. A strong deal box
protects the rods, which extend beyond
the box at each extremity, and carry a
fine scale. The microscope is so ar-
ranged that a point on the ground
several feet away can be read as well
as one on the rod at the distance of
a few inches. This is accomplished by
means of an object-glass of long focal
distance, in the center of which is in-
serted another of short focal length.
Beneath the microscope is an adjustable
screen, so perforated as to permit the
use of the smaller glass when the light
is cut off from the larger object-glass.

The microscope is held in position by
two rings attached to horizontal arms
projecting from a vertical cylinder. The
cylinder is supported by a stand which
rests upon levelling screws. By the aid
of these screws and of an attached level
the microscope may be rendered vertical.
The microscope is capable of a slight
vertical movement, whereby the focal

VAN NOSTRAND S ENGINEERING MAGAZINE.

adjustment is perfected. On the cylin-
der opposite the microscope, is a tele-
scope held by a bracket, which serves as
a counterpoise to the microscope. A
graduated scale may be substituted for
the telescope, and when read by the tele-
scope of the preceding microscope stand
in connection with a signal set up on
the line of the base in advance, it serves
to indicate the direction of the bar. The
telescope is constructed for making these
simultaneous readings in a manner simi-
lar to that employed in the microscope.
It consists of a small lens placed in the
tube and capable of such motion by
means of a rack and pinion as to bring
the scale to view in the same field with
the advanced signal. The use of a double
object-glass in base-line apparatus is
probably due to Haswell, though he em-
ployed the device in a crude form, He
made the two halves of the object-glass
of his microscope of glasses of different
focal length. Apparently Porro's ap-
paratus is superior to those before de-
scribed, and actual use has shown this
to be a fact.

The base is measured by placing four
microscopes on trestles, approximately
aligned at a distance of three meters
apart. The single measuring bar is then
transferred between successive micro-
scopes and the scales read. This instru-
ment, as improved by Ibanez, has been
used in the Spanish survey, a platinum
rod being substituted for steel.

For the measurement of secondary
bases, either as a verification or as preced-
ing the primary triangulation, it is neces-
sary to have an apparatus which shall be
of easy manipulation, light and durable
construction, and shall, without an over
nicety, be capable of comparative exact-
ness. For this purpose an apparatus
was constructed by Hilgard and others
of the Coast Survey, which is described
in the Coast Survey Keports of 1856-57.
It consists of a single rod encased in a
wooden box. The temperatures are
read by means of inserted thermom-
eters, and by means of a spring arrange-
ment contacts are rendered quite ac-
curate. The trestles permit of consider-
able vertical motion, which is obviously
of great importance over a comparatively
rough base.

Despite the exceeding delicacy of base-
line apparatus, it still admits of improve-

ment. If some method can be found to
eliminate the error arising from unequal
rates of expansion and contraction, and
if permanent changes of length can be
obviated, something of importance will
have been gained.

Bache's apparatus has been very thor-
oughly tested in the measurement of a
base at Atlanta, twice in winter and twice
in summer ; the probable error being
± 1.16u,-u, denoting one millionth of
the length measured. The probable
error of Colby's apparatus is stated as
±1.5u. Struve has placed the error of
his base as ±0.8w, which Clarke regards
as incorrect. The error of Bessel's ap-
paratus for a base of 2488m. ±is 0.59w;
For Porro's measurement the error
is ±0.32; for the base at Madridijos,
14664.5m., it is estimated at ±0.11u.

Comparisons might be made of the
relative accuracy of different construc-
tions by means of the probable errors of
base measured. But it is obviously not a
just method, since the length of the base
is directly proportional to probability for
error, aud the probable error is some
function of the temperature as regards
amount of change and rapidity of
its variations. The number of bases
measured with any form of apparatus
being but small, it is evident that the in-
fluence which the probable error, ob-
tained by the measurement of an ad-
ditional base upon the average probable
error of the instrument, will be consider-
able. If such comparisons be made, the
final probable error of a single appara-
tus should be determined by a com-
parison of the probable errors of the
bases which it has measured, the range
of temperature and length of base enter-
ing as weights, and the probable errors
thus obtained should be compared upon
a similar basis.

Such a comparison, however interest-
ing theoretically, is practically unim-
portant, since it has been shown con-
clusively, that Bache's apparatus is
unapproached for the ease and rapidity
with which it may be manipulated,
though perhaps slightly inferior to
Porro's in accuracy.

No fewer than two German expeditions
will come to this country to observe the
transit of Venus next year.

BLASTING I'N'DKR WATER.

BLASTING UNDER WATER.

By J. DEUTSCH.

From " Wochensehrift des Oestexreiohisohen [ngenleillMUld Arohitekten Yrreiiic," for Abstracts of

institution of civil Engineers.

Thk author

delegate

of the Aus-
trian Engineers and Architects Associa-
tion, attended the experiments conducted
by Major Lauer before a commission, ap-
pointed by the Imperial Minister for
War, to report upon his method of blast-
ing under water, by means of a charge
laid upon the surface of the mass to be
operated on, and fired by electricity.

For carrying out this operation an or-
dinary river flat or barge is employed ;
over the stem two beams are rigged out,
in which a couple of uprights, connected
at the top by a cross beam, are fixed ; in
the center of this cross beam there is an
iron stirrup ; the uprights are further
strengthened and stayed by a couple of
longitudinal ties.

A movable grating forms the floor of
this overhanging stage at its extremity,
and across its entire width there is a row
of apertures through which the sounding-
rod works, after passing through the
stirrup on the cross beam, and which to
gether regulate the position and direction
it is desired the rod shall assume.

The rod itself is made up of several
lengths of 1^-inch gas-pipe, each length
being fitted at one end with a solid iron
mandril, at the other with a strong coup-
ling. A chain attached to its lower ex-
tremity enables it to be lowered or raised
by hand from the deck of the flat. This
arrangement permits of the rod being ad-
justed in almost any position, and so as
to reach any point within a circle of con-
siderable area at the bottom of the water.
The soundings, however, are all taken at
an angle which by a simple calculation
gives the true vertical depth, all neces-
sary data being known. The depth may
vary without being perceived and alter
the angle, which might have the effect of
changing the position of the blast ; on
this point the jury expressed preference
for a system of vertical rather than of an-
gular soundings. For the purpose of
these experiments a mass of gneiss trav-
ersed by veins of quartz was selected,
situated in the bed of the Danube near

Kreus, and at a depth varying from 9 to 1 1
feet, the surface velocity being 10 £ feet.
The experiment occupied nine consecu-
tive dajrs, or six hundred and six working
hours, and gave an average performance
per day of ten hours of three hundred and
fifty soundings and seventy-two blasts,
each sounding occupying twenty-five sec-
onds, and each shot from four to five
minutes ; the rest of the time was spent
in altering the position of the barge. The
total number of shots fired was three
hundred and ninety-nine, on which 294
lbs. of dynamite were expended, and 43
cubic yards of rock removed. The force
of the current washed away the debris,
and the mass thus removed was ascer-
tained by soundings taken shortly after
each explosion ; had this been practica-
ble later it is probable greater results
would have been recorded. The cost per
cubic meter was found to be 12 gulden^
6 per cent, less than it has been estimated
similar work at the Iron Gate, performed
in the ordinary way, has cost.

A comparison of the system commonly
adopted and that recommended by Major
Lauer shows that the distinctive features
of the latter do not so much lie in the
fact that the charge is simply laid upon
the object to be operated upon, without
drilling or loading a hole, but rather in
the ease and rapidity with which the
charge is laid, and the precision with
which the operations of sounding and
blasting can be conducted. Besides, it
must be remembered that the very ob-
stacles which render the present system
tedious and expensive, viz., great depth
of water and strong currents, actually
contribute to the economic success of the
Lauer system, which puts blasting under
water almost on the same footing as
blasting on land.

The cost of blasting operations gener-
ally, whether above or below water, de-
pends on the structure of the rock rather
than its hardness ; and the local peculiar-
ities in each case, whatever they may be
on land, are certainly much exaggerated

100

VAN NOSTRAND7S ENGINEERING MAGAZINE.

when encountered under water, where
the sense of sight is inoperative, and that
of feeling, mechanically supplemented by
the sounding rod, alone available. Under
the present system, especially where the
water is deep and the stream rapid, the
operation of drilling the hole is attended
with uncertainity and great difficulty,
and, if during the process the water vary
considerably in depth, a satisfactory com-
pletion of the hole is almost impossible.
This, together with the expense of the
staging required, and the time occupied
in removing and replacing it before and

after each explosion, and preventing the
bore-hole silting up, contribute to make
the present system, even under the most
favorable circumstances, a most expensive
one ; so that, even before the invention
of dynamite, the plan of depositing free
charges of gunpowder on the surface
was resorted to in the years 1858-60 for
blasting operations in the harbor of New
York, with favorable results.

With dynamite the same system was
further employed on the coast of Dal-
matia, but with unsatisfactory results
due probably to local peculiarities.

WIND MEASUREMENTS.

From "Nature."

Since the time of Hooke the accurate
measurement of the wind has formed an
object of experimental research. That
philosopher, if not actually the first to
invent an anemometer, at any rate ap-
pears to have been the first to write
upon the subject, which sin^e then has
occupied the attention and exercised the
ingenuity of many scientific men. The
main result of these efforts was well
shown last week at the exhibition of
anemometers organized by the Meteoro-
logical Society. The President, in an
interesting historical address, stated that
the number which had been invented was
at least one hundred and fifty, and up-
wards of forty of these were collected,
besides photographs and drawings of
many others. The exhibition was by
kind permission held in the library of the
Institution of Civil Engineers, at whose
weekly meeting two papers, on the design
of structures to resist wind, and the
resistance of viaducts to gusts of wind,
were very opportunely read.

It is not by any means generally recog-
nized that there are two distinct objects
for which the measurement of the wind
is necessary; these are: (1) the deter-
mination of the actual motion or trans-
ference of the air itself ; (2) the investi-
gation of the effect of the wind. The
two societies above mentioned well repre-
sent these two objects of anemometry,
and all the instruments are included in
one or other of the two classes, which
are said to measure respectively the veloc-

ity and pressure of the wind. These
terms, though convenient, are slightly
misleading, as it is really the impulse of
the wind which is in both cases measured
— in one by its effect in producing the
continuous rotation of a vane or set of
cups, in the other by its statical effect
upon a pressure board or column of air
or liquid.

From the nature of the wind it is evi-
dent that nothing less than a continuous
graphic record could be of much service,
and but little progress was made until
the invention, about fifty years ago, of
self-recording instruments of both classes.
The late Dr. Robinson, F.K.S., contrib-
uted more than any one else to the es-
tablishment of the velocity anemometer
which, by the addition of Mr. Beckley's
self-recording apparatus, is undoubtedly
a model of mechanical invention. Mr.
Follet Osier, E.R.S., as the result of
much persevering labor and skill, has
given to the world a pressure instrument
of great excellence, and of this and the
former, both of which may be regarded
as the best types of the two classes, it
may fairly be said that much improve-
ment, at any rate in mechanical construc-
tion, can hardly be expected.

As to the tabulation of results, this is
conducted with the most scrupulous regu-
larity. Since 1874 the Meteorological
Office has published hourly numerical
records, from its various stations, of the
direction and other elements of the wind.
Quarterly records containing engravings

WIND MEASUREMENTS.

101

of the actual curves are also published.
These Litter have rather fallen into ar-
rears, the first volume of the new series
for 1876 having been only published in
18S1 ; but it is satisfactory to hear that
the work of completing them up to the
year 1880 is progressing, and it is to be
hoped that they will always be contin-
ued.

In the face of all this expenditure of
time and skill the meteorologist and the
engineer alike proclaim the unsatisfactory
state of the science. The engineering
aspect of the question, viz., the effect of
the wind, has recently excited consider-
able attention in consequence of the Tay
Bridge disaster in this country, and of
similar accidents abroad. It is evident
that with the increase in the size of en-
gineering structures, particularly in ex-
posed situations, the force of the wind
may become as great as that impressed
upon the structure by the action of grav-
ity. The recent account, in this paper,
of the proposed new Forth Bridge, was a
good example of the provision made for
wind pressure, not only on the completed
structure, but also during its construc-
tion. Notwithstanding this, the report
of the recent Commission on Wind Press-
ure substantiates the statements already
alluded to. This distribution of wind
pressure over any surface appears to be
very little understood, though the matter
is being carefully investigated by more
than one experimenter, and some results
have recently been published. It seems,
however, hardly credible that the maxi-
mum pressure to which a structure may
be exposed is almost as great a matter of
uncertainty ; yet such is the case. The
papers on wind pressure, above referred
to, in spite of the existence of so many
anemometers, endeavor to ascertain from
a variety of sources, such as previous
accidents, and reports of the effect of
wind in storms, what the probable maxi-
mum pressure has been, both, however,
assuming values for purposes of calcula-
tion far less than are actually reported.
In the same manner, the Commission
decided upon a limiting value only a little
more than 62 per cent, of a pressure
recorded by an anemometer, and believed
by them to have actually taken effect in
this country.

The fact is, that the motion of the air

is, beyond all expression, most com-
plicated. Were it not for this, there
would be no necessity for obtaining both
the velocity and pressure of the wind,
for there is, by a first principle of dynam-
ics, a fixed relation between these two
elements ; and if one were known, the
other could be, at any rate, approximately
deduced. In reality, any attempt to treat
the wind as having steady motion for
more than a very small distance in space,
is certain to involve serious error, and
the complications which are introduced,
from even slight disturbing causes, seem
quite beyond the powers of investigation.
The engineer is concerned both with pre-
judicial effect of the wind upon structures,
and its useful effect upon wind-motors.
In both these cases the conditions are
such as to greatly interfere with the
steady motion of the wind, and the effect
due to locality must be estimated and
allowed for. The meteorologist needs
observations of the wind at all elevations,
and as pointed out by Mr. Laughton in
his address, particularly at higher ones,
where, judging from the experience of
aeronauts, the motion of the wind is
nearly as complex as below. Until the
motion of the wind is better understood,
weather forecasts must be more or less
unreliable, and what has been said with
reference to the mechanical excellence of
the present anemometers and the regular
tabulation of results, must not lead to
the idea that there is no room for im-
provement. On the contrary, there is
yet much to be done in directions which
can here be only briefly indicated.

First, there is great necessity for im-
provement in the lubrication of the in-
struments, especially of that portion
recording direction, so that in viewing a
weather chart of the Times it may be
certain that in light winds the arrows
really show the direction and not directly
the opposite one. Such an error as this,
perhaps from some distant station, causes
whole columns of the bulky hourly rec-
ords to be worse than useless.

Secondly, the reductions for the rela-
tive velocity of the wind and cups, if
made at all, ought not to be made, as is
at present the case, by a factor now well
known as the result of much costly inves-
tigation, to be erroneous.

Lastly, the locality of anemometers

102

VAN nostrand's engineering magazine.

should be more carefully selected, or at
least taken more closely into account, in
discussing the effect of wind in storms.

The importance of some reform in the
matter of wind measurement is obvious,

since it is only by continued observations,
under improved conditions, that a more
reliable and satisfactory knowledge can
be obtained of the aerial ocean in which
we live.

METHODS OF IMPROVING RIVERS HAVING A CONSIDER
ABLE FALL, AND WITH BEDS LIABLE TO SCOUR.

From "Les Annates des Travaux Publics," for Abstracts of the Institution of Civil Engineers.

Rivers with a considerable fall, and
flowing in a channel scooped out of a
very thick bed of gravel, resemble tor-
rents. When the water is high the fall
is fairly regular ; but when the water is
very low, a series of rapids occur at the
shoals, separated by nearly level reaches
in which the channel is deep. TKe re-
moval of one or more of the shoals by
dredging only leads to an increase of fall
at the rapids above, and is therefore, not
a satisfactory remedy. Another method
of regulating the fall in such rivers is to
restrict the channel within low parallel
embankments. Such a plan, however,
whilst concentrating, and therefore
deepening the stream, increases its
velocity, and a scouring of the bed con-
sequently takes place till a fresh series
of shoals and pools are formed, restoring
the river to its original condition. Two
methods of improvement have been pro-
posed for this class of river, namely, (1)
the restriction of the channel by low
training banks ; and (2) the erection of
movable weirs, accompanied by a par-
tial contraction of the channel. The
first method has been carried out on the
Rhone for the last twenty years, and the
last still remains to be tried.

1. Improvement by low training banks.
— The method adopted in the first in-
stance on the Rhone consisted in restrict-
ing the channel at shallow places by
lengths of longitudinal embankments,
giving it such a width that, with the
maximum discharge and the mean fall,
the depth should be 5^ feet. It is not
surprising that this plan did not effect
the desired result on such an irregular
river as the Rhone, whose depth varies
from 2 feet to 26£ feet, whose width is
from 430 to 1,640 feet, whose fall is
sometimes only 2£ inches per mile, and
sometimes reaches 31 feet per mile, and

whose bed is much scoured by floods.
The next plan tried was training the
river by embankments, following the
natural windings of the river, and placed
590 feet apart. Then, as the river
tended to form deep channels close to
the concave banks, and left shoals on
crossing from one concave bank to the
next, the banks were brought closer
together at these points of inflection, so
as to increase the scour at these points.
Though, however, the shallow places
were thus improved, the water-level was
lowered above, and gravel accumulated
below. The defects of the channel are,
accordingly, not removed, but their posi-
tions are shifted.

In order to regain, in the deep por-
tions of the river, the fall lost by the
contraction of the shallow channels, it is
proposed to erect compensating dykes,
cutting off the deep parts of the channels
at the concave banks, and thus to force
the river to scour out the shallower parts
and obtain a fall sufficient to compensate
for the lowering of level produced at
other places. This plan would doubtless
answer if the bed was sufficiently stable.
It is probable, however, that, with a bed
so liable to scour, the new channel would
become as deep as the old one, and the
increased fall would be lost. A system
of continuous embankments would s^t
the whole river bed in motion, and the
masses of gravel brought down might
break the banks and form shoals. Low
embankments, moreover, are dangerous
for navigation, as they create currents,
and vessels may be injured by ground-
ing on them.

2. Improvement by means of movable
weirs, and partial contractions of the
channel. — The contraction of the channel
by embankments improves that portion
of the channel, but lowers the water-

THE GREAT STRUCTURES ERECTED IN ITALY.

108

level. This lowering may be prevented
by the erection of a morable weir, tower
down the river, which keeps op the level
and thus maintains the depth of tin1
channel above. An illustration is given
of the movable weir which M. Paeqneaa
proposed putting up across the
Rhone, at Grigny. It has been de-
signed in accordance with the principles
laid down by M. Tavernier, namely, that
in rivers bringing down large quantities

of gravel, like the Rhone, thewier should
be worked from a high fixed bridge
above flood level, and that the movable
parts should be capable of being raised

out of the river. The movable weir,
when opened, would not impede the
flood discharge; and a portion of the
river would have a sill 3} feet below
low-water level, so as to afford an out-
let for the gravel traveling down the
river.

THE GREAT STRUCTURES ERECTED IN ITALY DURING

THE LAST TWENTY YEARS.

By C. CLERICETTI.
From '• Conferenze sulla Esposizione Nazionale del 1881," for Abstracts of the Institution of Civil Engineers.

The author chooses the bridges of iron
and stone erected during the last twenty
years as the structures which best exhibit
the progress of engineering science, and
he compares these modern bridges with
those built by the Romans. The charac-
teristics of these latter are grandeur, mas-
siveness, and durability ; of the former,
lightness, economy, and rapidity of con-
struction.

The Po between Pavia and the sea wras
never bridged by the Romans, but during
the last twenty years four bridges have
been built over it. The lengths of these
bridges are 577,762,427, and 400 meters,
1,900, 2,600, 1,399, and 1,312 feet respect-
ively, the spans varying from 213 to 250
feet. They are all girder bridges, sup-
ported on piers founded at depths of
from 60 to 70 feet below highest flood
level, and formed of iron cylinders sunk
by hydraulic process.

To show the difference between the an-
cient and modern systems of construction
the author compares the Roman bridge
across the Danube, one of the boldest of
their works, with the modern structures
on the Po. The former — 1,207 meters
(3,960 feet) in length — had twenty-one
wooden arches of 50 meters (164 feet)
span ; and the piers — founded on a ma-
sonry platform extending right across the
river bed — had a thickness of 17.7 meters ;
while the piers of the latter, though 28
metres high from the foundation, are less
than 3 meters thick at the top. The an-
cient piers had six times the thickness

required for a modern girder bridge, and
three times what would now be allowed
for masonry arches of 50 metres span.
The same immense piers were built
throughout the middle ages; the old
bridge at Verona, for instance, with two
arches of 28.54 meters and 48.70 meters
(93£ and 160 feet), has a pier 12 meters
thick, though only 3.50 meters high.

The author proceeds to point out the
superiority of the modem system of long
spans and narrow piers, in leaving the
channel free for navigation and the dis-
charge of floods, and avoiding the scour-
ing action, caused by obstacles to the
natural flow. In some cases old bridges
have so impeded the flow as to cause se-
rious inundations above bridge.

The ironwork of the great bridges over
the Po was imported from abroad, but
the Italians are now constructing their
own, some, spans of 75 meters (246 feet)
having been already built, and others of
larger .dimensions, up to 100 meters, will
shortly be commenced.

The author states that, with few excep-
tions, only one type of bridge — the lattice-
girder — is constructed in Italy, and re-
grets that little encouragement is given to
improvements in design. He mentions a
few arched bridges, among them being
that over the Celina torrent, which he
considers one of the best examples.

The author proceeds to discuss the sub-
ject of the incalculable strains to which
bridges are liable ; from the jjoints of sup-
port not being knife edges, as theory sup-

104

VAN NOSTRAND'S ENGINEERING MAGAZINE.

poses ; from the variations in cross sec-
tions ; from the vibration caused by pass-
ing trains, &c. Airy attempted to ascer-
tain the strain in a bar of iron from its
musical note, but the result was not satis-
factory. Better results are obtained by
instruments for measuring the contrac-
tion and elongation of bars during strains,
such as the apparatus of Dupuit and
Manet in France, and Castigliano's multi-
ple micrometer, which the author de-
scribes.

The experiments made with Dupuit's
apparatus upon all kinds of girders show
that the actual maximum strains are in
general less than the calculated, particu-
larly in arches and in the horizontal mem-
bers of straight girders.

Iron bridges are also exposed to danger
from corrosion, but the author states that
Mallet's experiments proved that an iron
bar 6 millimeters (0.238 inch) in thickness
would not be destroyed in less than 700
years.

The author then gives particulars of
some of the principal brick and stone
bridges recently erected. Comparing
modern with ancient structures, he points
out that the former are built with one-
third less material than the latter. In
ancient structures the ratio between the
thickness of the piers and the span varied
from one-fourth to one-half, while in
modern it has been reduced to one -sixth,
and even one -seventh. The average ratio
between the thickness of the arch at the
crown and the span was 0.086, while in
modern bridges it is from 0.040 to 0.031.

The two principal arched bridges erect-
ed in Italy during the last few years are
the Ponte Annibale and the Ponte del
Diavolo. Each of them has a span of 55
meters (180 feet), and thickness at the
crown of 2 meters, the versed sine of the
former being 14 meters, of the latter
13.55 meters. Circular openings 9.25
meters in diameter, are introduced to
lighten the haunches. These are the
largest masonry arches in the world, with
the exception of one at Chester of 61
meters span, and one on the Washington
Aqueduct in America of 67 meters. In
the year 1370, however, an arch of 72.25
meters (237 feet) span, and 20.70 meters
rise, was erected over the Adda, at the
Castle of 'J rezzo. This arch was consid-
ered the eighth wonder of the world, both

for size and for the short space of time-
seven years and three months — occupied
in its construction. The Ponte Annibale
and the Ponte del Diavolo were built in
twelve and ten months respectively.

Among recent improvements in detail
the author mentions the use of hydraulic
lime and cement, which allows the centers
to be struck very shortly after the com-
pletion of the arch ; and the use of sand-
boxes instead of wedges for slacking the
centers, a system which he strongly recom-
mends.

The two above-named bridges were
built almost entirely of brick, great econ-
omy being thereby effected as compared
with stone. The Chester bridge, of 61
meters span, cost £83 per square meter
of roadway ; the Ponte Mosca at Turin,
of 45 meters span, cost £105 per square
meter of roadway ; whereas the Ponte
del Diavolo cost onlv £34, and the Ponte
Annibale £24.

The author concludes by predicting
that the limiting span of brick and stone
arches has not yet been reached, and an-
ticipates the erection of spans of 100
meters.

Perhaps the strict enforcement of the
new plumbing law will be a good thing
for householders and plumbers. At least,
it should promote somewhat the condi-
tions of better health for the former and
better pay for the latter. It only seems
reasonable, however, that kitchen sinks,
wash-tubs, bath-tubs, hand-basins and
water-closets should be constructed in an
appropriately ventilated and disinfected
tower outside the main residence alto-
gether, but with convenient and comfort-
able access to such tower's conveniences.
In spite of all that metallurgists have done
and the most expert sanitary scientists have
devised, any but the most remote connec-
tion with the ordinary main sewers of
cities means more or less frequent deaths
in a family, not to speak of protracted,
obscure and annoying cases of illness,
which do not prove directly fatal. The
sanitary arrangements of the great " flat"
system of buildings now so popular de-
serve fully as much attention as the pro-
visions they require for the escape of
residents in case of fire.

CANDLE POWER OF THE ELECTRIC LIGHT.

105

CANDLE POWER OF THE ELECTRIC LIGHT.

By PAGET HIGGS, LL.D.
From Proceedings of the Institution of Civil Engineers.

II.

Mr. W. Sugg wished to offer a few ob-
rvations upon a different point to that
referred to by Mr. Jones. The author
appeared to have taken the cost of gas
in New York, when he might just as well
have taken the cost of gas in England.
The cost, however, was a matter which
must be worked out in practice, and if it
was found that the cost of the electric
light would be very much greater than
that of gas, it probably would not be so
much employed as gas. That, however,
1 tight be left to the future. The part of
the paper with which he wished to deal
was the first point, namely, the standard
sperm candle. The author asked what
was a sperm candle, and he had pointed
out that the light of a sperm candle was
that which would be given from the can-
dle 1/oot all round the light. That was
a very good way of expressing a sperm
candle, because it was practically what
could be got out of it for use, for read-
ing or for work ; but unfortunately it
was not the standard looked upon by
Parliament as being the standard sperm
candle. The light of a standard sperm
candle was the light given from a point
in the center of a candle, and the calcu-
lations with the photometer were made
upon that assumption, that the point of
light in the center of the candle was the
whole of the light of the candle. He
had found it practically an extremely
difficult thing, with such an arrangement
as that, to carry out experiments and cal-
culations with regard to lighting various
areas, because with that theory to deal
with, viz., the central point in the candle
being the whole of the light, it was evi-
dently a difficulty, when it had to be
worked out for estimating the degree of
illumination of areas. The plan which
the author proposed, of taking 1 foot
round the candle for that purpose was a
good one, and could be usefully adopted
for many purposes. As he had pointed
out before, the standard sperm candle
was an india-rubber rule, and it seemed
strange that for so many years it had
Vol. XXVII.— No. 2—8.

continued to be used as a standard when
so fallacious, and which was known to be
fallacious so far back as 1868, through a
series of experiments made by Mr. T. N.
Kirkham, M. Inst. C.E., then the engi-
neer of the Imperial Gas Company, in
which he showed how very different one
candle was from another. Those experi-
ments had lately been repeated, and he
supposed from time to time they would
be repeated again ; but what would be
the result of these repetitions he could
not say. The Standards of Light Com-
mission appointed by the Government
had also endorsed the opinion, given by
Mr. Kirkman and himself, that the stand-
ard of light adopted for England was a
bad one. There were other standards of
light which were really standards of
light, and were not such as that derived
from degrees of temperature, as the au-
thor of the paper seemed to desire. He
did not himself see what the temperature
of the flame would have to do with its
illuminating power, except, as Mr. Cromp-
ton had stated, with regard to the incan-
descent lamps. Incandescent lamps of
course would give a very much higher
illuminating power as the temperature
was raised ; and therefore in that respect,
supposing one incandescent lamp were
measured against another it might be
useful, but as comparing the illuminating
power of electricity with that of gas, or
any other standard, it seemed to him that
it was a bad thing, and would result in
erroneous statements. When there were
found differences in the illuminating
power of 16-candle gas of from 1J to 2
candles with the best candles obtainable,
it would be seen that when that was
magnified up to the high illuminating
power of the electric light, errors would
arise which were surprising. With re-
spect to the tables adopted by the au-
thor, he had introduced, as Mr. Cromp-
ton had observed, "heat-grammes," and
sundry other terms unintelligible to those
who did not follow very closely the line
in which he had been working ; but Mr.

106

VAN NOSTEAND'S ENGINEERING MAGAZINE.

Sugg could point out that there were
several standards at the present moment
better adapted for the purpose of testing
the electric than the standard candle.
There was first of all the gas standard
introduced by Mr. Vernon-Harcourt, one
which could be carried out for the pur-
pose of estimating the standard candle
accurately at any time and under any
circumstances. The method that he
adopted, taking a certain quantity of
pentane, a product of petroleum, distilled
in a certain manner, mixing a certain
quantity of it with air and burning it in a
proper apparatus, appeared to give a per-
fect idea of what a standard candle should
be. That was the only one, he believed,
in which the value of the light was an
exact standard candle ; but there were
others, for example, that of Mr. Keates,
in which he used spermaceti oil, and
burnt it in a lamp, producing a light of
16 candles, and that light was much more
easily used for the purpose of testing the
electric light. He had used it himself
for that purpose, and found it going for
weeks without variation, so that he be-
lieved it to be a much more reliable
standard than the sperm, candle. The
next one after that was a standard of two
candles made by Mr. Methven, assistant
engineer of the London Gas Company, in
which he used the ordinary common gas
supplied for lighting ; and if there was
as he said no variation in that standard
when used with common gas, and Mr.
Sugg believed there was a great deal of
truth in what he said, it would be cer-
tainly better than the candles, and that
notwithstanding there might be slight
variations in it ; this standard of his
would be found much more suitable to
the electric light. The next was a 10-
candle gas standard of his own, and there
were several others which were very use-
ful ; and if the electric light was to be
estimated for its illuminating power, it
would be better to estimate it by such a
standard as these than by the fallacious
standard adopted of a parliamentary
sperm candle. There was one remark
made by Mr. Crompton on which he
would make an observation, and that was
as to the manner in which testing the
electric light for illuminating power could
be carried out. In the case of gas, the
assumption was that the light was given
in a circle all round the burner — equal in

all directions — and nearly all round in a
vertical circle. It was not so with the
electric light. With the electric light
the light came from between the two
carbons, and the strongest light was in
one direction ; it did not light equally
raund the vertical circle, neither did it
light equally in the horizontal circle ;
because on whichever side of the center
the carbon rested, one side or the other,
a greater light was shown. It could be
seen with a Bunsen photometer that this
variation would produce very great errors.
With regard to the incandescent light,
that, of course, could be tested in exactly
the same manner as gas, except that it
must be tested as a flat flame burner;
because he presumed that the light was
given more strongly in the direction of
the one side of the loop than it was across
the loop, so that if the mean of the edge
and flat of the lamp was taken a very
good result would be obtained. But
with the arc-light it certainly did seem
necessary that a correction should be
made when it was tested with a photo-
meter horizontally or at an angle, for an
evident error existed in the value of the
result, caused by the fact of the light not
giving its light in all directions alike, as
supposed by the construction of the pho-
tometer. With the Jablochkoff light the
result more nearly approached that given
by a candle than in any other, with the
exception of the Jamil), which was the
reverse of the Jablochkoff. Either of
those could be easily tested in the man-
ner he had stated ; but with the arc-
lights it would be necessary to make the
correction, and he had not seen that that
correction had ever been made.

Mr. J. N. Shoolbred said, he wished
to refer to the tables contained in the
paper. There was a very material differ-
ence in the way they were arrived at,
which the author seemed hardly to be
aware of, arid which ought to be pointed
out. All the lights named in the first
table were lights that had been produced
and measured directly from the electric
machine, or the dynamo itself. The sec-
ond table, on the other hand, represented
the result of experiments carried out by
Sir William Thomson upon a single Swan
light, at which Mr. Shoolbred was allowed
to be present, and in which the Faure
accumulator battery was used, the cur-
rent being taken direct from that instead

CANDLE POWER OF THE ELECTRIC LIGHT.

107

of from the dynamo. The results showed
points of considerable interest, and, he
thought, opened a very large future for
incandescent-lighting where a steady cur-
rent was used. Sir William Thomson
not being fully satisfied with the photo-
metric measurements, and having to leave
town, allowed him to make some further
experiments, and the result of the second
m ries of experiments shown in the tables
and curves annexed. The series of ex-
periments was carried out upon a single
Swan light and a single Maxim light;
increments of current being made by
successive additions of five Faure cells at
a time. The photometric measurements
in the second case were carried out with
the instrument to which Mr. Sugg had
referred, and with Mr. Keates' 16-candle
sperm-oil lamp as the standard of refer-
ence. The oil consumed was accurately
weighed, and there was every reason to
believe that the measurements were car-
ried out accurately. The curves repre-
sented severally the candle-power, the
measured potential, the intensity of the
current, and the amount of mechanical
energy in HP. This last was the sim-
plest manner of putting the mechanical
energy expended; he quite agreed with
Mr. Crompton, that the author had need-
lessly complicated the paper by introduc-
ing gramme-degrees, foot-lbs., or heat-
units ; all of which could be deduced
from the ratio generally made use of —

that of candle-light per HP. The amount
of mechanical energy converted into
electrical energy was indeed the basis of
the whole or this mode of generating
electricity. In practice the condition of
incandescent lights, when working direct
off a dynamo-machine, and without an
accumulator, was represented approxi-
mately by the diagrams (see following
page). Such being the limit under the
ordinary conditions, the value of the in-
tervention of the accumulator was repre-
sented by the gradual progress towards
the right. It would be seen how greatly
the intensity of the light could be in-
creased, and at the same time its econo-
mic value raised, in proportion to the
current expended, by using the steady
current of a storage accumulator. In
another way the economy of these lights
could be augmented; inasmuch as their
life would be considerably lengthened
owing to the use of the steady current.
It had been mentioned, that if the incan-
descent-lights were urged beyond 16 can-
dles there would be a gradual deposit of
carbon on the glass, and the filament of
carbon would be destroyed. He had no-
ticed himself the phenomena referred to
of the deposit of carbon, but that was
owing to the improper use of the lamp ;
for if a lamp which was only intended
for 16 candles was pushed to 25 or 30
candles, there would of course be pro-
duced an extra strain. But to say that

Table op Comparative Experiments with Faure Accumulator on Incandescent

Electric Lights.

1. Swan Incandescent Lamp in Circuit.

Number of

E.M.F.

Current.

Light.

Mechanical Energy.*

Faure
Cells used.

Volts.

Amperes.

Standard
Candles.

Bees
Carcel.

HP.

Kilo-
granieters.

Heat Units
(Joule).

30
35
40
45

104

1.28
1 84
2.38
2.50

22.4

65.6

141.0

204.0

2.36
6.91

14.84
21 47

0.125
0.209
0.309
0.348

9.52
15.94
23.53
26.50

5.3

8.9
13.2
16 3

1. Maxim Incandescent Lamp in Circuit.

1.81

16.0

1.68

0.179

13.65

7.6

2.24

45.3

4.77

0.255

19.41

10.9

2.59

101.1

10.64

0.340

25.87

14.5

113

3.00

229 0

24.11

0.454

34.56

19.4

124

3.20

333.0

35.05

0.531

40.45

22.6

The mechanical energy lost in charging the accumulator from the dynamo is not included.

108

VAN NOSTRAND'S ENGINEERING MAGAZINE.

Comparative Experiments in Incandescent Electric Lighting
with Faure Accumulator.

Candles

Swan.

Current

50 Cells,

Light £• ;;,; Candles

Mec'l.Force \K^i^.H.P.
E.M.F, Wjf/j ~~ Volts
Current "~ ~ Amperes

Vert' I. Scales
100 Per Inch,

0.20 „ ,„

60 „ „

2 ii i>

CANDLE POWER OF THE ELECTRIC LIGHT.

109

incandescent-lights were limited by all
the makers to 16 candles was totally fal-
lacious ; because they could be made of
whatever candle-power was required.
Just the same as a gas-burner could be
made to comsume 2, 3, 4, or 5 cubic feet
of gas, so the resistance of the incan-
descent-lamp could be altered so that it
would give from 10 to 40 candles or more.
With regard to the proportion of candle-
light given off per HP. absorbed with
the incandescent-lighting, Mr. Swan had
himself some two years ago limited it to
from 150 to 200 candles at the outside
per HP. There appeared to be a great
deal of difference with regard to the cause
of the large discrepancy between the
proportion of light produced per HP. ab-

parties were here upon the platform, but
from those he begged to entirely abstract
himself. With regard to Table I., he
believed the results might have been
predicted a priori. It must be remem-
bered that the so-called electric light was
a thing of an exceedingly composite char-
acter. It had an outflow of rays that
were entirely incompetent, even when
they impinged upon the retina, to excite
vision. Years before the present amazing
powers of the electric light were devel-
oped, he had experimented upon the
light produced by a battery of fifty Grove
cells, which evoked what in those days
might be called a very powerful electric
light, and found the invisible radiation,
meaning by that the radiation which was

sorbed, with the arc over the incandes- 1 incompetent to excite vision, to be 90 per

cent system ; an explanation given some
time ago by Mr. C. F. Varley seemed to
point to the true cause. It was suggested
that a much larger proportion of the cur-
rent was used in warming up the carbon
to incandescence than was required to
pass from that stage to the production
of the arc ; and in this greater light-
giving value of this last portion of the
current might be found some explanation
of the apparent discrepancy. If what was
indicated by the diagrams about the use
of an accumulator in conjunction with
the dynamo was correct (practically the
substitution of the 40-cells vertical line,
in the diagrams, instead of the 30- cells
one), it might be argued that incan-
descent-lights might, by its use, be very
much more economical in their results
than they had hitherto been. The fact
that more duty could be got out of gas
when used in a gas-engine than when
used for illuminating purposes was not
surprising. In the report of the Com-
mittee of the House of Commons, in 1879,

cent, of the whole. He was afraid it was
impossible to get rid of this condition.
This invisible radiation appeared to be,
so to say, the substratum of the visible.
The luminous rays must be built, as it
were, upon the non-luminous rays. The
same was the case with the sun itself, as
Herschell was the first to prove. Miiller
found that the luminous rays of the sun
were only one-third of the total emission
by the sun; that the invisible, obscure,
calorific rays emitted by the sun were
two -thirds of the total radiation. In the
case of the electric light the invisible
rays were by one series of experiments
proved by himself to be 7.7 times the
visible ; and in another series of experi-
ments, made according to a totally dif-
ferent method, the invisible calorific rays
proved to be 8 times the visible. With
regard to the sun, as he had said, its in-
visible radiation was twice as great as its
visible radiation ; but higher in the at-
mosphere, above the screen of aqueous
that overspread

vapor tnat overspread the earth, if a
On Lighting by Electricity, it was point- 1 spectrum of the sun was obtained at a
ed out that the heat-giving properties of j great elevation, it would be found that
gas exceeded considerably the light-giving ; then the obscure radiation of the sun
ones. Bunsen had shown that the light- j approximated to that of the electric light,
giving properties were only 6 \ per cent. | He received a letter some time since from
in 100 volumes, whereas the heat-giving j a gentleman who had been experimenting
properties were no less than 87 per cent. ! at a height of 12,000 feet above the sea

Professor Tyndall remarked that he

had not dealt much practically with this Sierra Nevada Mountains in California,

in a very dry region of the earth in the

question of determining the candl'e-power
of the eJectric light. He had, in associa-
tion with Mr. Douglass, done something
of the kind, but that was a long time ago.
He noticed, of course, that contending

aod he declared that there was an enor-
mous extension of the invisible spectrum
of the sun in those regions. Probably
at the limit of the atmosphere the invisi-
ble radiation of the sun, would represent

110

VAN NOSTEAND'S ENGINEERING MAGAZINE.

six times the energy of the visible radia-
tion. With regard to the table, the au-
thor of the paper took into account the
total amount of power absorbed, and the
question was, how much of that power
was converted into luminous rays, into
those rays that were effectual for vision,
and how much into rays that were not
effectual for vision. On theoretical
grounds he should have inferred that
the table must be as the author had
stated, and that, as Mr. Crompton had
remarked, the more intense the power
was made by the introduction of a resist-
ing interval between the two carbons of
the arc, and the higher the electro-motive
force invoked to urge the electric current
across the interval, the greater was the
proportion of the luminous rays intro-
duced into the total radiation. In the
first lamps mentioned, the foot-lbs. per
candle-power was very small compared
with the smaller lights. This simply ex-
pressed, in the case of the Werdermann
and in the case of the incandescent-light,
that in the intense arc-lights a greater
fractional part of the total energy was
converted into wave-m©tion competent
to excite vision, than when less power
was used.

Mr. W. Atkinson did not know whether
the author had stated at what distance
the experiments had been made with the
light. He understood that there was
great difficulty in arriving at any conclu-
sion as to the power of the electric light,
dependent upon the different distances
at which the experiments had been tried.
He believed it had been discovered that,
even in comparatively very short dis-
tances, in a room within the space of a
few feet, very varying results would be
obtained. The rays of the electric light
were probably readily absorbed by the
atmosphere when humid, as Dr. Tyndall
had mentioned, in the case of the sun.
Then with regard to the economy or the
cost of gas, the element of the destruction
of fittings in a house had not been re-
ferred to. If the electric light and the
gas light were compared, it was clear
that, to a consumer, the electric light
would be more economical, because there
would be no destruction and no dirt.

Mr. J. N. Douglass said his expe-
rience with the electric light had been
entirely with arc -lamps. It was a pity
that the comparison in the paper as

to the cost of gas and of the electric
light, had not been made with gas in Lon-
don instead of in New York, because
the cost of gas in New York was about
$2 J per 1,000 cubic feet, while in London
it was about 3s. Following the figures
of the author, he found he had given a
4-light chandelier of 64 candle-power, as
costing per hour in New York 20 cents
for gas, the burners being of the effi-
ciency of the London standard burner.
A burner would give about 5 candles
per cubic foot of gas consumed ; there-
fore, the above result would be got in
London at the cost of about 1.8 per
hour, as against 8d. per hour in New
York. As Mr. Jones had pointed out,
the only cost given in the Paper for the
electric light was that of the motive
power, and that was stated to be 4.1
cents, being more than twice the cost of
the gas light in London. There ap-
peared here the same difficulty of com-
parison that was met with in lighthouse
illumination ; and, from his experience,
he might say that if the electric light
could be fairly compared with oil or gas
as consumed in lighthouses, it would be
found that, with the arc-light about ten
times the amount of light per unit of
cost was obtained with electricity above
that of gas. Unfortunately, the element
of cost of plant and of additional cost of
labor came into play; and up to a
certain intensity, at a lighthouse, oil was
the cheapest light. But then an inten-
sity could be attained ten times that of
the oil with the electric light ; and there
would be about five times the amount of
light per unit of annual cost than with
the oil; however, the first cost and
annual maintenance were doubled. If
that first cost could only be reduced to
that of the oil or the gas-light, electricity
would, no doubt, prevail. With regard
to the measurement of candle-power,
there" appeared to be difficulties with the
electrical mode of measurement ; and he,
for one, would not be "disposed to accept
any apparatus for electric light, unless
he measured the light photometrically
in addition to the system proposed by
the Author of the Paper, because, as
pointed out by Mr. Crompton, there was
the quality of the carbon coming into
play, which was liable to considerable
variation. It was quite possible in the
same bundle of carbons to get differences

(■Ml

< AXDLE POWER OF THE ELECTRIC LIGHT.

Ill

of quality of certainly 50 per cent. With after a good deal of disappointment and
regard to the candle-power, he saw no change, he eventually obtained lamps
difficulty in using an ordinary candle i which, in pairs, fairly represent what the
with cure. Any one who was used to it single lamps did before. It was prema-
could arrive at results, certainly within ture to attempt any comparisons either
5 per cent. ; and to measure the electric as to the illuminating power or cost of
light, which varied within an hour 50 per renewals, for it was quite clear that the
cent., surely the candle was near enough ! whole system was yet in its infancy. He
i unit of comparison. The great dif- could state from his own experience
ficulty with the candle was the difference that there was the widest possible
in color. That, was, however, easily got difference between the lamps supplied,
over, if it were wished to reduce the \ He had some lamps at the present time

actual candle-measurement to the in-
tensity at the actual candle-flame color
by coloring the electric light with yellow
glass, and bringing it to the color of
the candle.

Sir William Armstrong, President,

which had been in use from the. very
first, whereas he had also had some that
failed after a few hours' use ; therefore,
until the manufacture settled down to
something mature, and the difficulties of
starting were fairly got over, there could

said he had had considerable experience hardly be a judgment as to the capabili-

with the incandescent system of lighting
He had used it in his house in the country
for nearly a year. He had gone through
many troubles and difficulties, such as
early experimenters always had to en-
counter ; but, upon the whole, he could
decidedly say that his experience had
been satisfactory. No doubt the com-
parison of candle-power between the dif-
ferent systems of lighting was a very
important matter ; but it was by no
means the only consideration that pre-
sented itself. He commenced with at-
tempts to make the arc-light available
for domestic use ; and after trying
various systems and various arrange-
ments, he came to the conclusion that no
possible improvement that could reason-
ably be hoped for would make it suit-
able or desirable for domestic purposes.
He then tried Mr. Swan's system, and
with the lamps which he furnished in
the first instance, and which were made
very carefully, no doubt, by hand, the
endurance and illuminating power were
exceedingly satisfactory. He came to
the conclusion that each single lamp
gave about as much light as an ordinary
duplex kerosene lamp, usually estimated
al about twenty-five candles. When the
company commenced their operations,

ties of the lamps, either with reference
to endurance or illuminating power.
This much he could say, that no de-
ficiency of candle-power or endurance
such as had been attributed to them
would induce him to abandon the sys-
tem. Gas was an admirable means of
lighting in its proper place, but in
private rooms it was undoubtedly very
objectionable. The incandescent light
had no connection whatever with the
atmosphere, and therefore had no con-
taminating effect upon it ; it had very
little heating effect ; it was perfect in
color, perfect in steadiness, and in fact
was the perfection of lighting for domes-
tic purposes. That, at least, was his ex-
perience ; and he had no doubt that dif-
ficulties which had arisen, and were aris-
ing, would be got over, and that the in-
candescent lamp would attain to a
perfectly satisfactory state. The number
of lights in his house was sixty, that was
thirty pairs. He had more, but could
work that number at the same time.
The source of power was a turbine
situated nearly a mile off ; and with 7
HP. he was enabled to maintain those
sixty lights. Most of the lamps that had
failed had not failed through the actual
wearing out of the carbons so much as

they changed the system, and instead of : from defects in their manufacture, from
using single lamps, they used two lamps points at which there seemed to be some
in series — at least they recommended ; defect which made them liable to give
the employment of two in series, instead | way in use. He felt, however, sure that,
of one in parrallel. Owing, perhaps, to | when the manufacture of the carbons
imperfect experience, he found the dura- j were perfected, all difficulties of that
bility of the new lamps much less than : kind would be got over. The light in
that of the first lamps supplied ; but ! his case, using water power, was highly

112

VAN NOSTRAND'S ENGINEERING MAGAZINE.

economical. There was the cost of the
laborer's attendance upon the machine
at night to supply the sixty lights, and
the only other expense was the cost of
renewals, which would certainly not be
very serious, according to his past
experience. One point he might men-
tion was the extreme importance of hav-
ing an absolute uniformity of motion in
the generator. The smallest variation
immediately produced a disagreable
twinkle upon the lights ; and so sensi-
tive were they, that while he used belts
made in the ordinary way with joints, he
could count the revolutions of the
wheel; that was to say, every time a
joint ran over the pulley it made a suf-
ficient variation to cause a slight effect
on the light. He could not obtain an
absolute uniformity untill he used an
endless belt made life a flat chain of
leather links stamped out of the sheet,
and joined together by putting a pin
through, a form of belt now pretty
generally used in cases where very even
and . regular motion was required. He
was afraid that unless the gas-engine
was supplemented by means to obtain a
very steady and uniform motion, the
absolute steadiness of light which he
had attained would hardly be obtained
from it ; but no doubt there were means,
when attention was directed to the at-
tainment of that particular object, which
would be found to remedy any in-
equality.

Dr. Higgs remarked in reply, through
the secretary, that the results given in
the paper were intended partly to be
intercomparative, and partly were an en-
deavor to reduce the observations of dif-
ferent authorities to a common standard.
This common standard he assumed to
be represented by the " energy" absorbed
in the light-center. He did not suppose
that " temperature " and light were re-
lated ; but that if light were any form of
energy, then that light would be related
to the energy of the light-center ; he had
measured this energy in heat-units and
not in "foot-lbs. per candle-power," as
suggested, because he did not know
what a candle-power was, in which
ignorance it seemed he did not, judging
from the remarks of those who had
favored him with their criticism, stand
alone, and he thought he did not know
what a heat-unit was. Between the

energy as measured in heat-units, not
the temperature, he had found the re-
lation to be as stated. But besides
criticism, he had thought to elicit facts
and measurements from others.

CORRESPONDENCE.

Mr. K. W. Hedges observed that the
author, in referring to the way in which
he measured the electric light in com-
parison with the method adopted by Sir
W. Thomson and Mr. Bottomley, did
not mention what that method was. The
great difficulty with powerful electric
lights seemed to be the variation of their
color as compared with the present
standards, the sperm candle and carcel
burner. He thought that, failing a
better standard, the difficulty might be
obviated by photography, either as
adopted by Captain Abney by photo-
graphing the spectrum, or in a simpler
manner by photographing the luminous
crater in the positive carbon. The in-
tensity of the light was greatest at the
latter point, and by interposing glass of
known opacity between the light and the
sensitive plate, and noting the time taken
to produce a photographic image, the
comparative amount of light from any
two sources might be ascertained. He
noticed the author's opinion that incan-
descent lighting was theoretically six
times the cost of arc lighting. This
would make the incandescent light as
dear or dearer than gas, and might de-
ter the introduction of the electric light
into theaters and crowded rooms where
it was much needed. The cost of arc-
lighting was considerably less than that
of gas, the only drawback being the
color which did not harmonize with gas.
He thought the difficulty might be got
over by enclosing the arc lights in
colored globes so as to tone the light to
the color of gas. From an experiment in
one of the picture galleries at the South
Kensington Museum, he foand the loss
of light to be less with a suitably colored
globe than with an opal one. If two
or more arc lights were enclosed in a
lantern, the fluctuation of any one would
be less noticeable, and one could be turned
out if necessary. With a margin of six
to one in favor of such a light which
could not be at once detected by the un-
itiated as that from an electric source,
and which had all the advantages pos-

IMMMl

THK 0O8T OF ELECTRIC LIGHTING BY INCANDESCENCE.

sessed by incandescent lights, the saving
in cost would alone cause the arc 1 i «_r 1 1 1
to be preferred to the latter.

Mr. Radcliffi Wabd observed that if
the subject had been the cost of the
electric light as against gas, he had no
doubt that several engineers would have
been prepared to prove that, even on the
very restricted scale of electric -light in-
stallations now existent, gas could be
competed with. He would first direct
attention to the passage in the paper,
wherein it was stated that a Serrin Lamp
and Gramme Machine gave a light of
.'U)00 candle-power, when the arc resist-
ance was about 1£ ohm.; and that with
about the same arc resistance a Cromp-
ton lamp yielded a light of 3,600 candle-
power ; also in the case of the Gramme
and Serrin the weber or ampere current
was stated to be 45.7 ; in the case of
the Crompton lamp only 24. This, ac-
cording to his experience with good car-
bons, was what frequently gave 3,600
candles as " diffused beam ; " such an
extraordinary difference between the
Crompton and Serrin Lamp as 24 to 45.7
required some explanation. To put such
figures in the paper, without comment,
was misleading and puzzling to any one
not a practical electrical engineer. Why
was it not stated what were the machines
used, that was, what type ? He should
be particularly interested to know what
class of Gramme machine was used. The
author did not appear to think much of
the carbon element, whereas Mr. Ward

i agreed entirely with Mr. Crompton, that
the carbon question was most influential
and important, not only in arc but also
in incandescent lighting. According to
his experience, and indeed the point was
self-evident and could be easily foreseen,
one of the most important features in
the construction of incandescent lamps
was the form of the carbon filament re-
garded as a structure ; the chief point
being the proportion of indenting sur-
face to the total mass, and sectional area.
He thought, in using the electric light
for domestic purposes, it would be ad-
visable to employ a dynamo machine
during the day to " charge " accumulators
placed in some convenient position in the
house, and then work off the accumula-
tors at night direct to the lamps. This
method would be preferable on account

I of being able to work in a house with a

; lower electromotive force. With respect
to the comparative cost of the electric
light, he would not go into details ; but
the cost of lighting Whitehall, as now
practised by gas, was considerably more
than if it were lighted by an electrical
system, such as could advantageously be
employed. Finally, he would suggest
that the cost of lighting lighthouse lan-
terns by electricity might, in the not
distant future, be much reduced by ob-
taining the current from a large central
electric generating station in the neigh-
borhood ; say the South Foreland lights

i from " Dover Town electric generating

I station " that was to be.

THE COST OF ELECTRIC LIGHTING BY INCANDESCENCE.

By WILLIAM CROOKES, F.R.S., &c.
"London Times."

For more than six months I have had
the principal reception rooms in this
house almost exclusively lighted by in-
candescent electric lamps, the electricity
being generated on the premises ; and
as so many different opinions have been
given as to the expense of lighting by
incandescent lamps, some saying that
electricity is many times more expensive
than gas, while others maintain that it is
cheaper than gas, the results of my own
private experience in electric lighting
may not be without interest.

The dynamo machine — a small Burgen
— is driven by a 3^-horse power Otto
gas engine, which under favorable cir-
cumstances will develop 5-horse power.
Owing to the absolute necessity which
exists in a private house in this neigh-
borhood that there should be no smell
of unconsumed gases and no noise of
machinery either in the house or out in
the street to annoy my neighbors, it be-
came necessary to add silencing cham-
bers to the air inlet and the exhaust
pipe, and to carry the products of com-

114

VAN NOSTRAND'S ENGINEERING MAGAZINE.

bustion high up on to the roof. The ob-
structions thus put in the way of the
free working of the engine necessarily
affect the horse power, so that when a
further deduction is made for the power
absorbed in running the machinery when
no electricity is being generated, I find
I have not more than two horse power
available for the production of electric-
ity. This is far from sufficient to drive
the dynamo machine to its full power,
therefore I lose greatly in efficiency both
in the engine and the dynamo machine.
However, I have only to deal with the
facts as they show themselves in my ex-
perience. The total necessary expense
of the installation has not exceeded £300,
including wiring the house and making
the lamps, although the actual expense
to me has been much more, as I had to
excavate and build underground rooms
for the machinery. Where stables or
outbuildings are available, or if a little
noise is not prohibited, a less expense will
give more available electricity, and where
steam power can be used the cost will be
diminished fourfold. The gas engine
requires five minutes' attention every day
to fill the oil cups and start it. Once
started, it will go on without attention
for six or eight hours. It is overhauled
and cleaned once a week; an engineer
does this on a Saturday afternoon, at a
cost of 2s. 6d.

The maximum electric current which I
can get is 11.5 amperes through an ex-
ternal resistance of 12 ohms. The lamps
fed by the current are distributed as
follows :

In the library I have ten 20-candle
lamps ; in the dining room I have ten
20-candle lamps ; in the drawing room I
have a cluster of twenty-one 4-candle
lamps in an electrolier in the center of
the room, and six 20-candle lamps. One
or two lamps are in other parts of the
house ; the total number of lamps about
the house being about 50. I cannot,
however, have this number alight at
once, as the machine as at present driven
will not feed so many. It is, however,
sufficient to light any two rooms per-
fectly, and the third partially.

Switches are placed in cupboards in
each room, so as to turn any desired
combination of lamps off and on. Main
keys, cutting off the whole of the cur-
rent at once, are placed in the engine

room, and also in my laboratory at the
place whence the main wires diverge
to the different rooms

Owing to inexperience in adjusting the
strength of the current to the kind of
lamp used, and to the variety of systems,
&c, I was then testing, the breakages
during the first three months were some-
what numerous. For the last three
months, however, since passing the ex-
perimental stage and settling down to
a definite system, I have used lamps
made by myself, and during this time
only one lamp has gone.

The gas burnt in the engine when the
machine is feeding its maximum number
of lamps (twenty- two 20 candle lamps) is
about 550 cubic feet in five hours, cost-
ing at 3s. 2d. per thousand Is. 9d. As-
suming that the light is required on an
average five hours a night all the year
round, this would come to £2 9s. a
month, cr £31 17s. per annum.

To obtain, not an equal amount of
light, but a fairly good light from gas, to
replace this amount of electric light,
would take 30 gas burners, each burning
5 feet per hour, or 750 cubic feet in five
hours, costing 2s. 4Jd., or £3 6s. 6d. per
month, or £43 4s. 6d. per annum.

The expenses, therefore, per month
stand as folows :

Electricity —

Gas consumed in engine .... £2 9 0
Engineer once a week to clean

and oil machinery 0 10 0

2 19 0

Lighting by gas alone. ..... 3 6 6

Balance in favor of electricity

per month 0 7 6

Or per annum £4 17 6

I have here charged only the current
expenses. Strictly speaking, I ought to
charge interest and wear and tear, but
these are more than counterbalanced by
the incidental advantages of electric
lighting. With it the ceilings do not
get blackened, the curtains are not soiled
with soot and smoke, the decorative
paint work is not destroyed or the guild-
ing tarnished, the bindings of books are
not rotted, the air of the room remains
cool and fresh and is not vitiated by the
hot fumes from burnt or semi-burnt gas,

THE CONSTANT SUPPLY AND WASTE OF WATEB.

115

while tire-risk is almost annihilated, as
no lucifers are used, and the lamps are
high up out of reach.

In the above statement I have com-
pared electricity with gas as an illumi-
nating agent. This is giving gas ;m un-
fair advantage. The twenty-one electric
lamps in my drawing-room do not re-
place gas jets, but wax candles, whilst
the incandescent lamps in the dining-
room replace candles and oil lamps.
The actual expense of these per night
comes to three or four times the cost of
electric illumination.

Moreover, I am producing my electric-
ity at an extravagantly dear rate. The
dynamo machine works only about half

power, and this greatly reduces its effi-
ciency ; while Messrs. Crossley tell me
that a consumption of over 100 feet of
gas per hour ought to give nie double
the power I get out of the engine ; and
doubtless it would do so were it not for
the back pressure produced by the
silencing boxes.

When electricity is laid on to our
houses as gas is, all these extra expenses
and difficulties will disappear ; and if, as
I hope I have shown, electricity, heavily
handicapped as it is in a private house,
compares favorably with gas even in the
matter of cost, it will necessarily be far
cheaper than gas when it is supplied
wholesale from a central station.

THE CONSTANT SUPPLY AND WASTE OF WATER.

By Mr. GEORGE F. DEACON, M. Inst., C.E.
A Paper read before the Society of Arts.

The waste of water is an evil, the
author urged, of the highest importance,
and one happily that may be prevented
at a comparatively insignificant cost.
By "waste" he meant not misuse, but
loss by leakage between the point where
a supply enters the towns and the taps
or other domestic fittings. This waste
he divided into two kinds, "invisible"
being generally underground, and always
incapable of detection by superficial ex-
amination ; and " visible," being gener-
ally above ground, and otherwise cap-
able of detection by superficial examin-
ation. The loss from invisible waste is,
under ordinary circumstances, very rarely
detected, unless the amount is so great
as to impoverish the supply to neigh-
boring houses beyond the limits of en-
durance. In the case of visible waste,
however, generally caused by defective
house-fittings, the conditions are essen
tially different; sooner or later, the
plumber is called in, and repairs of some
kind are effected. As compared with
the hidden waste, therefore, individual
cases of such superficial waste are of a
more or less intermittent character. The
continuous waste, and the aggregate of
intermittent leaks, amount to a certain
fraction of the whole supply. Take the

case of a £40 householder, with his wife,
three children and one servant, six per-
sons in all ; if he draws on an average,
15 gallons per day for each person, that
is 90 gallons per day in all, he is a very
large consumer of water indeed ; but if
in any part of his premises, above or be-
low ground, there is a leak no larger
than the diameter of a moderate-sized
sewing needle, discharging water con-
tinuously under a pressure of 45 lbs. per
square inch, his share of the water sup-
ply is at once doubled, and if the needle
leak were stopped, two houses instead of
one could be supplied. The aggregate
sectional area of 1,667 such needles is one
square inch. It has been ascertained
that such invisible leaks are exceedingly
common, and that they vary in size from
the sewing-naedle, or even less, to the
square inch, or even more, in which last
case the single leak under the assumed
pressure of 45 lbs. per square inch,
would supply 2,000 such households, or
6,000 persons. The number of these
leaks, although in the aggregate large,
is small as compared with the leaks from
domestic fittings, causing visible waste,
but owing to their much greater average
size, and to the much greater pressure
under which the water flows through

116

VAN NOSTEAND'S ENGINEERING MAGAZINE.

them, the total waste from these invisible
defects often greatly exceeds the total
waste from superficial defects.

By three classes of figures and their
combinations, we can therefore represent
by diagrams all the modes of flow which
occur in practice. The first mode, con-
stant in velocity, and long in duration,
representing the two classes of waste, in-
visible and visible, and shown by lower
and upper rectangles respectively. The
second mode, also constant in velocity,
but of comparatively short duration, rep-
resenting the draught of water through
a tap, without a cistern between it and
the water main. The third mode, vary-
ing in intensity, quickly attaining its
maximum, but slowly diminishing, caused
by the passage of water through a ball-
cock into a cistern. Now, in any ordinary
case of water supply, these three modes
of flow co-exist, and their resultant from
noon on one day to noon on the follow-
ing day, is distinctly shown from minute
to minute, by the position of the upper
horizontal line on the diagram. Such a
diagram may be automatically repro-
duced by the motion of the water enter-
ing any district through the main sup-
plying that district, and thtit the facts
thus made known lead to important re-
sults. Having explained these diagrams,
the lecturer proceeded to show each of
the methods which have been employed
for the detection and prevention of
waste.

The first and simplest, but crudest of
methods, consists merely in restricting
the supply, by turning off the water at
the main. Owing to its extensive adop-
tion, there are millions of people in this
country to whose houses the water comes
only during 20 to 100 minutes a day.
This most harmful and most expensive of
methods for the restriction of waste, is
commonly known as intermittent sup-
ply.

Its evils are : 1. Ordinary cisterns for
the storage of portable water are danger-
ous, on account of the great difficulty of
keeping them constantly clean, while the
mode in which they are commonly con-
nected with water closets, renders them
still more dangerous. Under intermit-
tent supply, such cisterns are neces-
sary : under constant supply, they are
not necessary. 2. When, under constant
supply, the flow is daily intercepted, the

water left in the main and pipes gradu-
ally finds its way out at taps opened in
the lower parts of the district, and at de-
fects in the pipes or fittings. By this
means, the main is partly emptied, and
an in-draught takes places at defects in
the higher parts, to fill the void thus oc-
casioned. This in-draught maybe air, or
it may be — and frequently is — foul water.
The leaks most difficult of detection, and
therefore most permanent, are those im-
mediately above sewers and drains ; the
air thus forced into the main is frequently
that of sewers or drains. The water
similarly forced in is too commonly that
of foul closet-pans, the outlets of which
are stopped, or partly stopped. This
foul air or water is infused into and
served with the next day's supply. 3.
The whole of the twenty -four hours' sup-
ply for use, misuse, or waste is concen-
trated in a fraction of the twenty-four
hours. If the duration of supply is one
hour, the average rate of flow in the
mains must be twenty-four times as great
as with a constant supply, in which the
waste has, by other means, been simi-
larly reduced. The result is that, during
that hour, the pressure in the mains is
greatly diminished, and the consequence
in case of fire is shown in London by the
almost universal necessity for the use of
fire engines. When a fire takes place
during the intermission of supply —that
is during twenty- three hours out of the
twenty-four — there is no water to be had
in the service man until the arrival of the
turncocks, and the pressure is then so
far diminished by the leakage that fire
engines are still necessary.

The second method of restricting
waste, like the last, is simple, but ex-
pensive and crude. It consists in
nothing more than replacing all, or
nearly all, the pipes and fittings,
both public and private, with new
ones of a better kind. The first well-
known case of its adoption was by the
Norwich Water Company, who obtained,
in 1859, the necessary Parliamentary
power to apply this method in its broad-
est sense.

The application of the method was
instrumental in reducing the rate of
supply during 24 hours from 40 to about
15 gallons per head — which compara-
tively low consumption was maintained
by one house-to-house inspector to about

THE CONSTANT SUPPLY AND WASTE OF WATER.

117

30,000 persons. Unless it can be shown
that defects incapable of repair exist in
all the fittings, and that the mains and
pipes are. throughout, in such a con-
dition that existing leaks, even if de-
tected, could not be usefully repaired,
this method is obviously wasteful alike
of the money of the public and of the
water authorities. When such work
has been performed, the system of dis-
tributing mains and fittings is left pre-
cisely as it would be in new water-
works, carried out with the same skill
and care. But the fittings and pipes do
not remain new : they deteriorate rapidly,
and if left to themselves, their condition
is, in time, little better than before their
renewal. Obviously, therefore, absolute
renewal, even under the most perfect
conditions, is not of itself sufficient.

The third method of restricting waste
is simply the system of house-to-house
inspection carried out without renewal
of the nttings or pipes. But house-to-
house inspection is incompetent to dis-
cover invisible waste, and for each visible

powers to enable them, if necessary, to
adopt the second method of restricting
waste — i. e., the method of renewal. But
the townspeople disallowed the expendi-
ture necessary to support the bill in
Parliament.

The first method of restricting waste, viz.,
restricted or intermittent supply, had for
many years been applied. The second
method, house-to-house inspection, and
repair or renewal of detected cases, had
long been in operation, with a yearly in-
creasing staff. There was no known
method left, and it, therefore, became
imperatively necessary to investigate the
causes of waste more minutely, and, if
possible, to devise some method by which
a larger proportion of that waste could be
brought to light. An experiment, ex-
tending over a population of 31,080 per-
sons, was then made, at very consider-
able cost, by the Corporation of Liver-
pool. That experiment was directed to
the determination of the exact nature of
the waste, and it was proved that the
different methods of restricting waste

leak detected, the inspector of necessity ' produced the following results respect-
visits many private premises in which no ively : — The population of 31,080 per-
waste is taking place. | sons, as left by ordinary house-to-house

By the fourth method of restricting inspection, with one inspector to each
waste the examinations are confined to 86,000 persons, required a supply of 33.5
the particular premises in which waste is gallons per head per day ; on the appli-
actually taking place, and the hidden as ! cation of intermittent service, by which
well as the superficial waste is detected, the supply was limited to 9^- hours out
In the year 1865, Liverpool had adopted of the 24, the rate of supply became 19.5
the first method of restricting waste, \ gallons ; by the detection of waste by

baring and examining, and, if necessary,
renewing the pipes, and by employing
nearly all the Liverpool inspectors in this
comparatively small district, the supply,
notwithstanding the abandonment of the
first method, and the restoration of con-
stant service, was reduced to 13.3 gal-
lons. The results of this costly experi-
ment were ascertained by 14 ordinary

restricting
viz., the intermittent system, and had I
combined with it the second method, or
house-to-house inspection, on the scale
of one inspector to 111,000 persons. This
number was gradually increased, until in
1870 it became one inspector to 58,000
persons ; in 1871 one inspector to
43,000 persons ; and in 1872, one in-
spector to 36,000 persons. During the

same time the first method of restricting positive and intergating meters placed

waste was applied with increasing strin-
gency, by diminishing from time to time
the number of hours supply per day
until it was reduced to 9 out of 24 ; but,
notwithstanding these precautions, the

upon the mains supplying different sec-
tions of the district. Among other
things, it was conclusively shown that
complete renewals of either mains or fit-
tings was an unnecessary and wasteful

rate of supply gradually increased, and process, and that if only the locality of

the condition became so critical that two
or three such dry seasons as sometimes
occur in succession would have brought
about a disastrous water famine. In this
emergency the Liverpool Corporation
proposed to seek for Parliamentary

each leak could be brought to light its
prevention could be effected at a com-
paratively insignificent cost.

The possibility of detecting the exist-
ence of a leak, by taking advantage of
the conduction of the sound caused by

118

VAN NOSTRAND'S ENGINEERING MAGAZINE.

that leak through the iron or lead pipes
t© some metallic surface upon which the
ear could be placed, had long been
known, and in isolated cases, where the
existence of a leak had been suspected,
this method had been practiced. Moder-
ate quiet is necessary for this per-
formance, and moderate quiet in towns
can only be obtained at certain hours of
the night. But to apply such a method
as a system had hitherto been properly re-
garded as impossible, because of the ne-
cessity it involved for supervision of a kind
which has never been found practicable.
It was obvious, however, that if, by any
means, such a method could be system-
atically adopted and maintained — results
unknown before in connection with the
detection of leaks would accrue. If, for
example, men at moderate wages, in-
stead of going from house to house dur-
ing the day, and finding merely a visible
defect in, perhaps, every tenth house,
could be sent out in the dead of night,
with stethoscopes, and with means of
access to metallic communications with
the mains and pipes, sufficiently close
together ; and if a record of their success
or failure could be made by an instru-
ment beyond their control^ the certainty
of success would be as great, at least, as
the certainty with which a tell-tale clock
keeps a watchman awake.

Stop-cocks upon the house-service
pipes provided the metallic communica-
tions accessible from the street ; they
also provided a ready means by which a
flow through any one of the house-ser-
vice-pipes, to waste, could be easily shut
off. This shutting off produced an in-
stantaneous change of flow in the main,
and all that was necessary, therefore, was
to devise and place upon the main an
instrument capable of recording by means
of a diagram, the flow in units of volume
per unit of time at each and every
instant. Such a diagram cannot be pro-
duced by adding clockwork and pencil
to any integrating meter, positive or in-
ferential, except by the employment
of complex mechanism, but it can be ob-
tained by an instrument of a simpler
and totally different kind. This waste-
water meter, in its most recent form, is
so connected with any water main that
the whole of a supply to a population
of 1,000 to 4,000 persons passes through
it, and that, without any loss of pressure

measurable by ordinary pressure gauges.
A diagram is drawn automatically, in
which the rate of movement of the paper
past the pencil is clearly shown. The
paper is prepared with vertical hour
lines, and with horizontal quantity lines,
and is readily fastened to the drum of
the instrument. Such a diagram shows
in gallons per hour the rate of flow at
any time of the day or night. It shows
by the perfectly horizontal line, at some
time of the night, a perfectly uniform
flow, caused by water running to waste,
and the varying flow of water caused by
use and misuse, distinguishing it from
the waste by the varying line.

Mr. Deacon then explained the modes
in which the waste-watermeter system
is employed in practice, taking as
an example the case of a town con-
taining 100,000 persons. The number
of waste- water meter districts into which
such a town could be conveniently di-
vided would depend entirely upon the
arrangement of the water mains, but it
would probably be fifty or sixty. Upon
the main supplying each such district, a
waste-water meter is placed in such a
manner that the whole of the water
supplying that district passes through
the meter. If in such a town, any sys-
tem of inspection whatever has been
adopted, there are probably not less
than three inspectors. If they are fairly
intelligent men, they may be retained,
and no more will be required.

Having fixed the meters and outside
stopcocks upon the house service pipes,
if such stopcocks do not already exist,
all ordinary systems of inspection are at
once set aside. One inspector fixes
blank diagrams at the rate of 20 a day,
and brings to the office as many dia-
grams from meters upon which they
may have been placed from one to seven
days before. In a few days from the
commencement of the work, the manager
has before him the whole 60 diagrams,
with the waste per hour visible at a
glance, and with the waste in gallons per
head, entered by the inspector or a clerk
on the diagram in the space left for the
purpose. He finds that out of the 60
districts the diagrams show that in 101
the waste per head is five times as great
as in 10 others, and that without any
reason by which any divergence might
have been anticipated..

THE CONSTANT SUPPLY AND WASTE OF WATER.

119

Instead of wasting the energy of his
men upon all the districts in rotation,
the manager now concentrates his atten-
tion upon the most wasteful 10, and with
the worst of these he begins his work.
Two inspectors receive orders at night
to visit that district, and, in order that
they may confine themselves to the right
blocks of houses, and omit none, they
are provided — in Liverpool, at least —
with a small plan of the district, show-
ing the houses supplied through the
meter in question. Having reached the
district between 11 and 12 o'clock, p.m.
one of two methods is adopted.

By the first and most general method,
the stopcocks are sounded in rotation,
by using the ordinary stopcock turning
key as a stethoscope, and any stopcock
through which water is heard to be run-
ning is shut off, the time and number be-
ing noted by the inspector. The shut-
ting off and time of shutting off are sim-
ultaneously recorded by the meter on the
main, to which the inspectors have no
access. On the pavement, above each
stopcock so closed, the inspector marks
a cross in chalk. If after closing a stop-
cock the sound continues, it is obviously
caused by waste from the main, or be-
tween the stopcock and the main. It is
then generally heard at several stop-
cocks, and by its relative loudness at
each, an approximation is made to its
position. The footway and the carriage-
way pavements are then sounded, until
a spot of maximum noise is found.
Here, again, a chalk mark is left, which
rarely fails to show the position of a
burst pipe or ferrule to the day in-
spector, who, with his laborer, visits the
district on the following day. At the
end of two to four hours, the round of
the whole district has been made, and
the inspectors find themselves again not
far from the meter. They next close the
main stop -valve, near the meter, and
leave it closed for a minute or two.
Commencing with this valve, they then
reopen all the closed stopcocks, which
are readily seen by the chalk marks, and
return to the night office, where each in-
spector writes in copying-ink on the
left-hand side of a book the particulars
of his inspection. By the second
method — rarely necessary except when
waste has already been very much re-
duced— the whole of the stopcocks are at

first shut off without sounding. On the
return journey, they are opened one by
one, and sounded; the result is obvi-
ously to magnify the sound resulting
from small leaks, supplied by cisterns
with ball taps. At (.) o'clock on the same
morning the day inspector receives a
press copy of the night inspector's re-
ports. He visits those premises, and
those only, in or under which waste is
reported to be actually taking place, and
the work of many days' inefficient house-
to-house inspection is efficiently per-
formed in one. On the same evening he
writes in red ink, opposite the night in-
spector's report, the result of his ex-
amination. He also issues the necessary
notices for repairs or renewals. On the
same day the manager or his clerk re-
ceives and records the meter diagram
from the district in question. He sees
by that diagram the time during which
the night inspectors were continuously
engaged, and he sees the exact amount
of useful work performed in that time.
It would not be possible, even if the in-
spectors had access to the meter, to
elude this knowledge. He sees, more-
over, the total quantity of waste de-
tected, and one month hence he will see
by another diagram the result of the day
inspector's efforts to stop it.

The secret of the success of this sys-
tem, as compared with that of house-to-
house inspection, is due to the facts : 1.
That the inspectors are always working
in the most wasteful districts. 2. That
the time occupied in inspection is greatly
shortened. 3. That the hidden as well
as the superficial waste is detected.

That the time occupied in inspection
is greatly shortened may be shown as
follows :

Under the ordinary system of house -
to house visitation, one man, in one day,
can inspect, on the average, the dwell-
ings of about 180 persons. Under the
waste-water meter system, the wages
paid to him generally suffice for the thor-
ough inspection of the premises occu-
pied by more than 1,000 persons. The
invisible as well as the visible waste is
detected. This invisible waste frequent-
ly exceeds, on the average, one-half the
whole waste, and where a thorough
house-to-house inspection, occupying a
given number of men a given time, and
detecting a given quantity of waste, is

120

VAN nostkand's engineering magazine.

followed by an inspection under the
waste- water meter system, it is generally
found that the same number of men suf-
fice to detect two to three times the vol-
ume of waste in one-fifth the time.
When, in conjunction with this fact, we
take the additional advantage to the lat-
ter system of having the inspectors al-
ways engaged in the most wasteful dis-
tricts, its relatively high efficiency is
sufficiently obvious.

Whatever results have been obtained
by any other method can be brought
about by the method advocated by the
author, much more cheaply, both to the
water authority and to the householder,
and with far less trouble and annoyance
to all concerned. This system has been
applied within the last nine years to dis-
tricts containing about 1,700,000 persons.

The mode of preventing waste when
detected is not affected by the manner
of its detection. It will be agreed on all
hands, that when it is decided to replace
a fitting or pipe, that fitting or pipe
should, like those to be used in new
premises, be of the best possible kind,
and should be fixed and adjusted in the
best possible manner. .The soundness
and efficiency of water fittings can only
be conclusively determined by taking
each to pieces, examining each part in
detail, and finally testing the whole un-
der pressure. Such an inquisition finds

defects in a certain proportion of the fit-
tings made by firms even of the highest
and most deserved repute.

The fittings used in Liverpool are
such as encourage, rather than discour-
age, the proper use while preventing the
waste of water. No pea ferrules or
other obstructions to the flow of water
are permitted; no taps in which the
duration of flow is limited are required,
except for out-door stand pipes ; and
water-closets are not allowed to have
new cisterns providing a flush of less
than two gallons.

The respectable local plumbers have
been invited to sign an agreement to
conform to the water regulations issued
by the Corporation. The incentive to
them to do so is the advertisement of
their names on the backs of the waste-
water notices. A plumber's name may
at any time be erased if he fails to com-
ply. In practice, it is found that work
is rarely performed except by men
whose names appear in the list, and that
there is, therefore, no sale except for fit-
tings tested and stamped by the proper
officer of the Corporation.

The cost of adopting the method ad-
vocated has always been insignificant in
comparison with the value of the results
obtained, and is generally entirely cov-
ered by the saving of water in from six
to 12 months.

THE NEW EDDYSTONE LIGHTHOUSE.

"The Nautical Magazine."

On Thursday, the 18th May, the new
tower, which, daring the last three and
a-half years has been in course of con-
struction upon the Eddy stone reef, was
formally commissioned by H.R.H. the
Duke of Edinburgh. The ceremony was
attended by the Trinity yachts Galatea
and Siren, having on board the Deputy
Master, Sir Richard Collinson, aud many
of the Elder Brethren and officials of the
Trinity House, as well as sundry dis-
tinguished visitors ; the Admiralty ves-
sels Vivid, Trusty, Perseverance and
Car r on, took out the Mayor and Corpo-
ration o,f Plymouth, and the authorities
of Davenport and Stonehouse. In ad-
dition, a number of steamers brought out

the general public, and the scenes, both
as the flotilla steamed out of Plymouth
Sound, and as the numerous vessels
grouped themselves around the Eddy-
stone reef, was singularly picturesque.
The weather was brilliant, there Being
just sufficient wind to impart a lively
motion to the water, and a general ap-
pearance of- briskness and vigor to the
scene at the rock.

The history of the proceedings in con-
nection with the new tower may be
briefly stated as follows :

In 1877 it was determined in conse-
quence of the undermining of the rock,
on which Smeaton's tower was built, to
erect a new tower, the old building being

THE NEW EDDYSTONE LIGHTHOUSE.

121

at times subject to tremors and vibra-
tions of a somewhat alarming nature.

After several careful surveys, a suit-
able base for a new tower was found on
a rock at a distance of 40 yards from the
old lighthouse in a S.S.E. direction, the
only drawback to the selected rock being
that its top is only just above the level
of low water, and the foundation there-
fore had to be laid below the level of low
water. The design of the new tower and
the general arrangements in connection
with the organization of the staff and
direction of the work were left entirely to
Mr James N. Douglass, the Engineer-in-
Chief of the Trinity House.

The personal superintendence of the
work was entrusted to Mr. T. Edmond,
who possessed considerable experience in
lighthouse building, and Mr. W. T.
Douglass, the son of the engineer-in-chief
above mentioned.

In the winter of 1877 and spring of
1878 the preliminaries were all arranged,
and on the 17th July, 1878, the first
landing on the rock was made, five
others being made before the month was
out. The first necessity was to build a
coffer dam for the protection of the men
while working, and to excavate, cut and
bench the rock so as to prepare it for re-
ceiving the foundation courses. With
the exception of a few small stones being
carried away in October, the season was
a successful one, and was prolonged un-
til 21st December, when operations were
suspended for the winter, about one-
fourth of the protecting coffer dam hav-
ing been completed, and 1,500 cubic feet
of rock excavated ; 40 landings having
been made, and 129 hours of work ac-
complished.

It should be mentioned that this
period, while the men were working be-
low the level of low water, was the most
perilous. Not more than three hours at
a time could be spent on the rock by the
working party. From about three-
quarters ebb to quarter flood tide was
the utmost limit of their stay, and during
that interval the utmost energy of all had
to be exerted. With a rough sea, land-
ing on the rock was simply out of the
question, but often when at work, the
party having perhaps effected an easy
landing, the sea would get up, and then
it would be necessary for all to seize
their tools and hurry off to the boats as
Vol. XXV1L— No. 2—9.

quickly as possible. Delay would prob-
ably mean being hauled off through the
water, for no boat could venture near the
rocks while the seas were breaking upon
them.

The urgency for the construction of
the coffer dam was so great that every
nerve was strained to complete it. Work
was even carried on on Sundays, when
fair weather and a good tide offered.

In 1879 the first landing was made on
the 24th February, and work proceeded
rapidly. The coffer dam was completed
by June, and then the shears, winches,
&c, were set up for landing the stones.
The method of carrying on the work may
be briefly described as follows: The
twin screw-steamer Hercules, employed
in carrying from the work-yard at Ores-
ton to the rock the material for the new
tower, could carry 120 tons of stone,
<&c, and occupied a little more than an
hour in making the passage. On each
day, when there was a fair prospect of
landing on the rock, the Hercules left
Plymouth in time to arrive at the Eddy-
stone reef soon after the beginning of
ebb tide ; on arrival she was warped into
a position a very short distance from the
rock, and made fast head and stern. In
this position the vessel would be only
about 30 or 40 feet from the rock. On
the deck of the steamer a railway was
fitted, on which a truck conveyed heavy
loads, such as blocks of granite, bags of
bricks or sand, and barrels of cement, to
the stern of the vessel, whence they were
carried to the rock by means of a double
chain extending from a strong timber
framework on board, to the crane on the
rock, and worked over the pulleys by one
of the powerful steam winches of the
steamer. By this plan a three or four
ton stone could be hoisted with compar-
ative ease from the ship's deck up to the
required height, and then dropped into
its prepared place.

On the 19th August, 1878, H.K.H. the
Duke of Edinburgh, Master of the Trin-
ity House, in the presence of H.R.H. the
Prince of Wales, Admiral Sir Richard
Collinson, Deputy Master, and many
other Elder Brethren of the Corporation,
laid the foundation stone of the new
tower. After this the work sped along
and the season closed on 19 th December
with eight courses laid. Strange to say,
on the 21st and 22d November the men

122

VAN ISTOSTRAISTD'S ENGINEERING MAGAZINE.

worked on the rock for several hours by
candlelight! As many as 131 landings
in the rock were made in 1879, and 518
hours of work accomplished.

On the opening of the season of 1880
much anxiety was felt as to the effect of
the winter storms upon the work which
had been left. On the 25th February
the first visit was made, and it was found
that the iron jib of the landing crane had
been carried away, otherwise no damage
whatever was done. The setting up of
the stones was briskly proceeded with,
and the tower rose above the level of
high water. The operations were not
now quite so arduous ; a longer time
could be spent on the rock, and landings
effected more easily. The masonry of
the tower was in this season completed
up to the 38th course, 110 landings hav-
ing been made, and 657 hours of work
expended up to the 9th November, the
date of the final landing in 1880.

In 1881 the first visit to the new
tower was on the 18th February and the
hoisting in and setting of stones went on
with great rapidity until June, on the
first day of which month H.R.H. the
Duke of Edinburgh, who, as Admiral
Superintendent of the Naval Reserves,
was on coast-guard duty in the neighbor-
hood, laid the top stone of the tower.
The extraordinary quickness with which
the work so far had been executed, more
rapidly in proportion to dimensions than
any rock lighthouse previously under-
taken, is explained by Mr. Douglass as
being due chiefly to the special steam
machinery and appliances for pumping,
rock-drilling, and hoisting materials, &c,
with which the steamer Hercules, em-
ployed upon the work, was fitted.

The tower consists of 2,171 stones
containing 63,020 cubit feet or 4,668
tons of masonry. Smeaton's tower con-
tained only 988 tons of stone. The sheer
weight of the new tower is probably
sufficient in itself to enable it to with-
stand a considerable force of wind or
wave, but in addition to this every stone
is dovetailed above, below and on all
sides, as well as being joined with cement
to the stones adjoining, on a plan which
is an improvement of Smeaton's method.
In Smeaton's tower four living rooms
besides the lantern were provided, but in
the new tower there are nine rooms each
more lofty and commodious than any of

those in the old building. The new
tower has a cylindrical base from which
the main lighthouse-shaft springs. The
advantages of this plan are that the cir-
cular ledge formed by the cylindrical
base offers great facilities for landing
from a boat, and at low water affords a
convenient promenade for the keepers.
A life-line, which is fixed around the
tower just above the level of the plat-
form, might be extremely servicable to
shipwrecked sailors, if any such unfortu-
nates succeeded in getting a foothold on
the ledge.

Up to a height of 25^ feet above the
level of high water, the tower is solid,
with the exception of a large water tank
let into the solid. The stone of which
the new tower is constructed is granite
of the best quality, from the quarries of
Dalbeattie in Scotland and De Lank in
Cornwall, by far the larger quantity
coming from the latter. Many of the
blocks weighed more than three tons,
and were dressed and fitted at the
quarry.

The Lantern. — The lantern surmount-
ing this noble tower is a splendid piece
of work, constructed by Messrs. Chance
Bros. & C >., of Birmingham. It is cylin-
drical, 16£ feet high (which is higher
than lighthouse lanterns usually are
made, but this is necessary to accom-
modate the two burners, one above the
other, which are placed there) and 14
feet in diameter. A very careful ar-
rangement for thorough ventilation of
the light-room is provided, which is most
essential, having regard to the great
heat which may at times be developed
when the lights are burning. Fresh air
can be copiously admitted through valves
in the lower part of the lantern, and
through a grating in the lantern floor
which communicates with open windows
in the service room below. The burners
are thus plentifully supplied with, the
necessary oxygen, and streams of cold
air, ascending all round near the inner
surface of the glass of the lantern tend
considerably to check the condensation
of moisture on the panes, which other-
wise might seriously interfere with the
effectiveness of the light.

The, lantern, however, is unimportant
compared with the apparatus inside for
producing the light. In Smeaton's day
the illumination was produced by 24

THE NEW EDDYSTONE LIGHTHOUSE.

123

candles of six to the pound, arranged on
a chandelier. No reflector of any kind
aided the candle lights, and no provision
was made for preventing the rays going
in directions where, so far as the seaman
was concerned, they were wasted. Early
in the present century, however, the
candles were superseded by 24 oil lamps
with reflectors, by means of which the
light was greatly improved, both in
regard to its power and its concentrated
usefulness. In 1845 again a change
was made, the Argand lamp and re-
flector being disestablished in favor of
Fresnel's new dioptric systen, by which
one large central flame was employed,
the rays from which were magnified and
refracted (t. e., bent in the direction re-
quired), by means of an arrangement of
lenses and prisms surrounding the light
at a distance of two feet or more on all
sides, in form of a beehive. This ap-
paratus, with a four- wicked lamp, has re-
mained in operation until now, but the
light in the new tower is of a vastly
more important description than those
which have preceded it in the old tower.

In speaking of a lamp having four
wicks, it should be explained that these
four wicks are concentric, or they may be
described as four tubes of wick, the
larger encircling the smaller ones, the
innermost being about one inch, the
outermost about three inches in di-
ameter. When burning all the four
wicks are alight and yield a fine body of
flame. Of late years Mr. Douglass has
caused the intensity of the flame to be
greatly increased by the addition of two
more wicks of proportionately larger
circumference than the outermost wick of
the four-wick burner.

Two of these six-wick burners are
fitted, one superposed on the other, the
vertical distance between the two being
about 6^ feet.

For ordinary purposes the upper lamp
only will be used, the value of the light
being 722 candles ; with both lamps
burning, the combined illuminating
power is said to be equivalent to a
quarter of a million of candles, or about
six thousand times the intensity of the
original candle-light of Smeaton's time.
What effect this enormous mass of light
concentrated into flashes will have upon
thick fog remains to be proved, but there
can be little doubt that in misty, hazy,

slightly foggy, rainy or snowy weather,
the flashes will be serviceable to the
mariner at distances to which the old
light could never have reached, even had
it been of the same elevation as the new
light.

Although in 1859 Mr. J. W. D. Brown
provisionally protected an invention, the
main feature of which consisted in the
employment of two or more tiers or rows
of lenses superposed with a separate
light or set of lights for each tier or
row, yet to Mr. J. R. Wigham, of Dub-
lin is due the credit of having first prac-
tically utilized this idea, with his biform,
triform, and quadriform gas apparatus.
He employs two, three or four sets of
gas burners superposed, each burner
consisting of several rings of flame pro-
duced by concentrically arranged gas
jets, the value of each burner being aug-
mented by a glass dioptric apparatus.
These superposed lights yield a splendid
effect when in operation, as at Galley
Head, on the Irish Coast.

The glass apparatus at the Eddy stone
by which the effect of each burner is
augmented and economized consists of
a twelve-sided drum, each side, also
called a panel, 6 ft. 3 in. in height and
1 ft. 8 in. in width, being formed by a
central lens, or, as it may popularly be
called, a bull's eye, and surrounded by
concentric rings of larger bull's eyes, by
which the same effect is obtained as
though a portion of one huge lens of
great thickness and weight, as large as
the whole panel, was employed. For
purposes which will presently be ap-
parent, the two bull's eyes of the adjoin-
ing panels are brought close together,
very much as though they were two
eyes squinting, so that only lengthways
they are in the middle of the panel. On
the rotation of this twelve-panelled drum,
with the inside central light burning,
each bull's eye with its surrounding
rings carries round a concentrated beam
of light, which becomes visible to the
outside observer as soon as by the rota-
tion of the apparatus the focus of the
bull's eye falls upon him. Now two
bull's eyes are, as have been stated,
brought close together, so close indeed
that a small portion of each is cut off,
consequently a very short interval occurs
between the flash of the first and that of
the second reaching the observer ; thus

124

VAN NOSTRAND S ENGINEERING MAGAZINE.

it will be seen the two flashes occur in
quick succession, and then nearly half a
minute elapses before another pair of
squinting eyes come around and dis-
charge their two flashes. This descrip-
tion applies to one light only ; with the
two lamps one over the other, two drums
superposed are employed, one for each
light, the two being identical in all
respects and arranged so as to co-
incide exactly with each other. The
height of the whole apparatus is con-
sequently 12 ft. 6 in. and with both lights.

burning a magnificent effect is obtained.
The optical apparatus was manufac-
tured at the works of Messrs. Chance
Bros. & Co., of Birmingham, the calcula-
tion of all the angles of reflection, &c,
being made by Dr. Hopkinson, F.R.S.,
a work which it is essential should be
done with the highest degree of ac-
curacy, in order that the lenses and
prisms may be so adjusted as to inter-
cept the rays of light proceeding from
the lamp, and bend them so that they go
out seaward in the desired direction.

ENGINEERING: PAST AND PRESENT.

Address of ASHBEL WELCH, President of the American Society of Civil Engineers,
at the Annual Convention at Washington, May 16th, 1882.

I do not propose this evening to
undertake any general survey of the en-
gineering field. For such a survey, I
refer you back to Mr. Chanute's address
of two years ago. I shall not attempt to
gJean after him. But 1 shall speak of
several disconnected subjects of present
interest, and give some reminiscences
showing the contrasts between the past
and the present ; and in such reminis-
cences I shall disinter the buried memo-
ries of some of the great engineers of
the past.

When we look around on the engineer-
ing works recently completed, or now in
progress or in contemplation, the first
thing that strikes us is their extraordi-
nary magnitude.

Prominent among them is the St.
Gothard tunnel, passing for 48,900 feet,
or more than nine and a quarter miles,
through the base of the great Alpine
chain which has hitherto been so formid-
able a barrier between southern and
central Europe, a thousand feet below
the vale of Urseren and the villages of
Andermatt and Hospenthal, and 6,500
feet, or a mile and a quarter below the
eternal snows that cover the crest of the
mountain. The cost was about $12,000,-
000, or nearly $250 per foot lineal. This
tunnel is nearly 9,000 feet, or a mile and
twc-t'iirds longer than the Mt. Cenis
tunnel, by far the longest previously
built.

Such stupendous works have been
made practically possible by the com-

pressed air drill, and the high explosives
now used. In my active engineering
days, rocks were drilled for blasting
only by the power of human muscle,
either by one or two men churning a
hole in the rock with a heavy rod some
six feet long, or by one man holding and
slowly turning a short drill, and another
man driving it into the rock with a
sledge hammer. Then came the steam
rock drill, then the compressed air drill.
The compressed air not only does the
work, but it ventilates, and its sudden
expansion cools the tunnel or the mine
where it is used.

The first, or one of the first tunnels in
this country in which the rock was
drilled by compressed air, was the
Nesquehoning, by Mr. J. Dutton Steele.
Since then many have been made by the
same means, one of the most memorable
of which is the Musconetcong tunnel, a
mile long, made under the direction of
Mr. Kobert H. Sayre. This difficult
work gave occasion for the valuable treat-
ise on tunnels by Mr. Drinker, who was
in immediate engineering charge of it.
The Hoosac tunnel, 24,000 feet long,
after a long continued struggle, was
completed several years ago, and is now
in use.

Among the tunnels now being con-
structed is one half a mile long under
the plateau of West Point, and another
4,000 feet long through the hard trap
rock of Bergen Ridge, at Weehawken ;
both on the line of the road now in con-

ENGINEERING: PAST AND PRESENT.

125

struction on the west shore of the Hud-
son. Nearly all the debris from the
latter is raised through shafts.

The project is now under serious con-
sideration of making a tunnel some 21
miles long under the straits of Dover. A
few years ago such a project would have
received only a laugh of incredulity.

The admiration of the world has not
yet abated for the boldest of arched
bridges vet built, that over the Missis-
sippi at St. Louis ; with its steel arches
of 500 feet span, its piers of heavy
masonry sunk to solid rock more than a
hundred and thirty feet below the high
water surface of the river, through shift-
ing sands, and during the most fearful
floods.

The Brooklyn Bridge, 1,595 feet> or
nearly a third of a mile long, over an arm
of the sea more crowded with commerce
than any other in America, and high
enough to allow a line of battle ships to
sail under it — is drawing to completion,
and will be (though perhaps only for a
few years, 'till something more stupend-
ous comes), one of the wonders of the
world.

Probably the boldest plan for a bridge
ever proposed, is that now in contempla-
tion over the Forth at Edinburgh, but of
which it is yet premature to speak.

Many very long spans and important
bridges are now in progress in this coun-
try, such as the one over the Missouri
by Mr. Morrison, but time does not per-
mit even a glance at them.

We are now so familiar with the suc-
cess of suspension bridges for railroads,
that we can hardly realize the almost uni-
versal disbelief in that success before
they were tried. The late John A. Roeb-
ling told me before his bridge was fin-
ished, that Robert Stephenson had said
to him, " If your bridge succeeds, mine
is a magnificent blunder." And yet, un
expectedly to the best engineers in the
world, the supension bridge over the
Niagara answers the purpose quite as
well as the tubular bridge over the St.
Lawrence.

The mention of the St. Lawrence re-
minds us of the great and interesting
improvement of that river now going on
under the direction of Mr. Kennedy.
The original low water channel between
Quebec and Montreal, had, in places, a
depth of only 11 feet. Now they are in-

creasing the low water depth to 25 feet,
with a width of 300 feet. The work is
done with bucket and chain dredges, ex-
ceedingly well adapted to the purpose.
Some of the buckets are armed with great
steel teeth which excavate the sold rock
(geologically Utica slate, but compact
rather than slaty in its structure), de-
taching and bringing up blocks some-
times containing several cubic feet.

If anything of the kind could astonish
us in this fast moving age, it would be
the rapidity with which, during the past
half dozen years, the construction of
elevated railroads in New York, and to
some extent elsewhere, has gone on. It
is of little use to find their aggregate
length, for in a few weeks any such esti-
mate must be corrected. There may now
be about thirty-three miles of such roads,
all double track. The average cost, in-
cluding stations and equipment, has been
about $800,000 per mile.

One of the cases in which a new con-
trivance effects a great revolution, is
that of the elevator. This has been in
use for perhaps a quarter of a century at
the Continental Hotel in Philadelphia,
and in a few other places, but is now
coming into general use, and is revolu-
tionizing the mode of building in our
great cities, especially in New York. A
block of buildings is not now extended
along a street as formerly, but is set up
on end, and a highway to the differen t
houses or parts of the block, is not hori-
zontally along the sidewalk, but verti-
cally through the elevator shaft. Sky
room is cheaper than earth room. It is
said that a lot on the corner of Wall and
Broad streets was recently sold for over
$320 per square foot, or at the rate of
$14,000,000 per acre! Equal to the sur-
face covered with silver dollars 5 deep.
These stupendous buildings will give
engineers and architects much to look
after in the way of foundations.

This reminds us of the Holly plan, in
limited use elsewhere for several years,
now going into extensive use in the city
of New York, of dispensing with private
fires for heating, and private boilers for
generating steam ; and furnishing heat
and steam power for a considerable dis-
trict from one great central set of boilers,
piled boiler over boiler, tier on tier, for
120 feet in height. This is one of the
operations most characteristic of the

126

VAN NOSTRAND'S ENGINEERING MAGAZINE.

present time. Nothing is to be done
now by the individual, but everything by
some institution, or corporation, or cen-
tral power, or great firm. Man has
ceased to be a unit, and become only an
atom of a mass. With the disappearance
of the things themselves, the dear old
phrases " family fireside," and "domestic
hearth," are rapidly disappearing.

Mr. Shinn and the Engineer, Mr.
Emery, have kindly given me some par-
ticulars respecting this transportation of
heat and power, but I can only refer to
one or two points. The first and most
obvious necessity is to prevent the escape
of the heat. This is done by enclosing
the steam-carrying pipe in a small brick
tunnel, with a flat cover on the top ; and
filling the space around the pipe, from
the bottom of the tunnel to the flat cover-
ing above, with mineral wood, which is
found to be an excellent non-conductor.
It is made by blowing a jet of steam into
a stream or jet of melted furnace slag.
The arch and covering of the tunnel are
plastered over with asphaltum, to exclude
all moisture. The loss of heat is said to
be very small. One of the great difficul-
ties comes from the expansion and con-
traction of the pipes, the range being
more than an inch in a hundred feet.
This is provided for by making the end
of each section of about 80 or 100 feet,
terminate in very flexible diaphragms
of thin copper, the diaphragms being
supported by stiff iron ribs.

Among the great enterprises in con-
templation, is the inter oceanic canal, or
the interoceanic railroad for large ships.
This is not the occasion for expressing
any opinion on any of the competing
projects. I will only say that if the
world is determined to have a sea level
canal, it makes a great mistake in not
getting fuller information about the San
Bias route.

Many' things that have been done by
this generation seemed beforehand far
less possible than the successful working
of the ship railway proposed by Captain
Eads. The difficulties are certainly very
great, but we can see how they may be
overcome. The real question is, whether
taking into account the expense of over-
coming those difficulties, the construc-
tion and operation of such railway will
be more economical in the end than the

construction and operation of some one
of the proposed canals.

The last year has been one of intense
activity, particularly in railroad construc-
tion. A year or two ago money was so
abundant, and, therefore, interest so low,
and so many capitalists, great and small,
were tired of letting their money lie idle,
that new enterprises of many kinds were
started, especially new railroads, and en-
largements of capacity of those already
in use. As the money market has ap-
proached its normal condition, some of
the new projects have been dropped.

It is instructive to look back and trace
the connection between the progress of
railroads and the financial condition of
the country.

Erom the year 1787 there has been a
financial catastrophe, or at least depres-
sion, in our country regularly every ten
years down to the year 1857. The cause
of this seems to be rather psychological
than anything else. It seems to have
taken the American business mind just
ten years to pass through the various
stages and degrees of panic after the
financial crash, through extreme cautious-
ness, moderate cautiousness, moderate
confidence, great confidence, extreme
confidence, recklessness, and then another
crash.

These decennial depressions were
modified by circumstances. That of
1817 was intensified by the effects of the
war of 1812 and by the failure of the
crops of 1816. That of 1837 was moder-
ated by the efforts of the United States
Bank, and part of its effects postponed
until the final failure of the bank a few
years later, which produced the inter-
calary depression of 1842. The effects
of the crash of 1847 were moderated
within two or three years by the dis-
covery of the gold in California.* The
crash of 1857 was intensified by the pre-
vious inflation from the gold excitement,
the rapid railroad construction in the
West stimulated by the land grants, and
its effect continued longer than usual on
account, first, of the apprehension, and
then the reality of civil war.

The effects of a financial crash do not

* That discovery was first made in digging the
foundati oil or the tail race of Sutor's Mill, by James
W. Marshall, who fifteen years before bad been a
boss on work going on under my direction, and whose
three sisters are still neighbors of mine.

ENGINEERING [ PAST AND PRESENT.

127

appear in the statistics of railroad con-
struction till a year or two after it takes
place, for if a road is well advanced
towards completion, it will probably soon
be finished, even during a panic. This
is shown in the statement following.

In consequence of the financial troubles
of 1841 2 the mileage of new railroads
opened in 1843 and 1844 fell off 71 per
cent, below that of the two preceding
years. Before the panic of 1847 had
time to reduce the increase of mileage its
effects were more than counterbalanced
by the discovery of golc} in California
and by the land grants, After the great
crash of 1857 the new mileage in 1859
and I860 fell off 57 per cent, below the
average of the three preceding years.

During the four years of the war the
new mileage was 64 per cent, less than
that of the four preceding or of the four
succeeding years!

Notwithstanding the excitement and
inflation after the close of the war, the
periodicity of the financial intermit tant
was broken, and no crash occurred in
1867. The causes are too recent and too
well known to require mention. Besides
the influx of money from the sale of our
government bonds abroad, the ocean
telegraph hastened the equalization of
interest on both sides of the Atlantic,
and the flow of money to the points
where it was wanted. A few years ago
the normal rate of interest in the West
was 50 per cent, higher than in the East.
Now there is but little difference. The
depression was postponed till 1873.

From the close of 1867 till the close
of 1874, when the effects of the panic of
1873 became visible in the statistics of
railroad extension, more than 4,400 miles
of railroad per annum were opened, twice
as much as the yearly average of any
similar period had been before. For the
next three years (1875, '6 and '7) the an-
nual increase fell off 69 per cent, below
the average of the preceding seven
years.

The troubles that followed the panic of
1873 were entirely different from those
that followed any of the decennial or
other panics previous to that time. They
were financial ; this was commercial. In
all the earlier cases the difficulty was
want of money, in this last case there
was, or soon came to be, a plethora of
money. Those were convulsions, this

was stagnation. There were more means
of production and of transportation than
there was demand for. If wealth con-
sists of such means, then the community
were suffering from excess of wealth.

The railroads opened in the United
States January 1, 1880, aggregate 86,500
miles in length, being 40 per cent, of all
the railroad mileage of the world. Last
year we had 93,600 miles, and this year
we have just about 100,000 miles. But
mere length is a very inadequate measure
of their magnitude. The terminal mile
of some roads has probably cost as mnch
as five hundred miles of some other roads.
At one time, and possibly now, the cost
per ton taken, on the first two miles of
the road from New York to Pittsburg,
was more than the cost of carrying that
ton over the next two hundred miles.
The increase in aggregate magnitude of
all the roads may be almost as much in
the enlargement without increase in
length of the old, as in the extension of
the new. We hear in more than one case
of thirty miles of additional terminal
tracks being laid at one point.

The diminished plethora of money, and
the greater caution now apparent, will, it
is to be hoped, moderate the increase of
the means of production and transporta-
tion beyond the demands of consumption,
so as to prevent another stagnation.

The investment in railroad property in
the United States is set down at about
5,000 millions, perhaps about one-eighth
of the value of all the property of the
country, real and personal.

When we speak of the extraordinary
magnitude of the engineering works of
the present day, we do not forget the
pyramids, temples, and fortifications of
Egypt and Chaldea. Some of them ex-
ceeded in magnitude anything that has
been made since. What makes it more
strange is, that the force that produced
them was almost entirely human muscle,
while now the work is done largely by
steam directed by human brain. Two
contrasts strike us as we look at the an-
cient and modern : the one was executed
by slaves and conscripts, with little or no
compensation; the other by free men,
glad to work for the compensation of-
fered. The old was for the glorification
of the few ; the modern for the use of
the many.

The stagnation that followed the break-

128

van nostrand's engineering magazine.

down of 1873, and the consequent low
rates of transportation, compelled the
managers of railroads to reduce the cost
to a point previously thought unattain-
able, by increasing the power of the en-
gines and the weight of the trains, by
more convenient arrangements, by more
service of the machinery, by cheaper con-
struction and repairs, by better machinery
and organizations of labor, and many
improved appliances for handling, and
by the stoppage of leaks generally.

American engineers and managers have
often shown that poverty is the mother
of invention. For example, they used
cross ties as a temporary substitute be-
cause too poor to buy stone blocks, and
so made good roads because they were
not rich enough to make bad ones. Amer-
ican engineers are, or at any rate, were
trained on short allowance of money. As
that is the best engineering which accom-
plishes the purpose at the least cost in
the long run, American engineering ought
to be of the best.

It is doubtless the fertility of resource
coming from the necessity of effecting
much with little means, which has created
a demand for American engineers in other
parts of the world. A few years ago the
Government of British India sent for an
American engineer, and the first thing
they asked him to do was to report on
their railroads from the American point
of view. Our lamented past president,
W. Milnor Roberts, was employed by the
Government of Brazil, as I judge from
what happened after he went there, to
train their engineers, educated in Euro-
pean schools, in American modes and
ideas.

Among the greatest of the projects of
the present day is the improvement of
the Mississippi River.

Towards it the eyes of our profession
and of the whole country have of late
been anxiously turned. It has overflowed
an extent of territory of more than 20,090
square miles, and destroyed millions on
millions of property and hundreds on
hundreds of lives. One of the most im-
portant engineering problems of the age
is how to restrain its ravages, as well as
to improve its navigation.

In order better to understand what the
Mississippi River Commission is doing
for these purposes, let us glance at a few
of the principles which, or some of which,

doubtless control the action of that com-
mission. Those principles are very sim-
ple, though their application is often very
difficult,

The quantity of solid matter of greater
specific gravity than water that a run-
ning stream is capable of carrying in sus-
pension, other things remaining equal,
increases with the increase, and decreases
with the decrease, of the velocity of the
stream. Like most cardinal principles,
this is so simple and obvious that it
seems ridiculous to state it.

It follows, from this, that when a stream
is loaded with such matter up to its car-
rying capacity, then, other things remain-
ing the same, if the velocity is decreased,
it will drop part of its load, and if the
velocity is increased, it will, if suitable
material is in contact with the current,
take on more load.

Mathematicians have calculated that
the difference in velocity between paral-
lel films of moving water keep the par-
ticles of solid matter afloat ; but, as is
obvious to the eye, and as Mr. Francis
has proved, running water does not move
in parallel films, and it is also obvious to
the eye that the suspended matter com-
monly moves more or less up and down.
The real motion is a compound of paral-
lel and ricochet movements, combined in
all sorts of ways and proportions, the
boiling and plunging movements increas-
ing with the velocity, the unevenness of
the bottom and sides of the channel, and
the presence of foreign objects and aqua-
tic vegetation, and being greater in pro-
portion to the whole volume of the water
when that is shallow. It is largely this
boiling movement which raises the solid
matter and keeps it afloat. With the
same velocity, the greater it is, the greater
the capacity of the stream to carry such
matter. Some of the causes, however,
which produce the boiling motion may
diminish the velocity, and so, on the
whole,- diminish the transporting ca-
pacity.

This is one. reason why the exact rela-
tion between velocity and transporting
capacity is so difficult to determine.

The same current will raise and carry
a greater weight of small than of larger
particles of the same form and material :
for the impact of the current against the
particle, tending to move it, is as its sur-
face, that is, as the square of its linear

engineering: past and present.

129

dimensions, while the weight and conse-
quent resistance to motion is as the cube
of the same dimensions. Flat particles
are carried mure easily than round or
cubical, for they have more surface in
proportion to weight. Of course a par-
ticle of greater specific gravity, as of trap
rock, is harder to move than one of the
same form and size of less specific grav-
ity, as anthracite. It takes eight times
the force to raise a particle of specific
gravity 3, in water, that it does to raise
one of the same size of specific gravity
1^. This shows why, in many cases, a
higher velocity carries no more weight of
solid matter per cubic foot of water than
a lower ; the higher velocity and greater
boil take up larger and heavier particles
than the lower, and a much larger amount
of transporting capacity is used up in
carrying them than in carrying an equal
weight of finer and lighter particles.

This is another reason why the exact
relation between velocity and transport-
ing capacity has not been ascertained ;
the sizes and specific gravity of the par-
ticles transported are not known, and
therefore their effect on total quantity
transported is not known.

This relation might perhaps be found
by some such experiments as the follow-
ing : 1st. Grind some suitable kind of
stone of uniform substance to fine pow-
der ; then, by sifting, separate the par-
ticles of the powder or dust into lots
according to size, each of uniform fine-
ness ; then see how much weight of each
of these sizes per cubic foot of water can
be carried in suspension at the same
velocity. 2d. Make the same experiment
with stone of different specific gravity,
sorting it into lots of the same sizes, the
water being kept at the same velocity.
3d. Try the same things with different
velocities. The facilities for doing all
this can probably be found at some ce-
ment mill.

The specific gravity of the bank furnish-
ing the silt, or of the bar formed by it,
or of the sediment deposited from the
water, gives no information of the size of
the particles, and little of their specific
gravity. Hence the transporting power
with the same velocity appears so dif-
ferent in different observations. Total
weight gives only partial information.

I should expect that the transporting
power would be as the square of the

velocity. I have washed out bars of
heavy sand by temporarily confining the
current over them, and its power of re-
moving the sand seemed to be about as
the difference in level of the water above
and below, that is, as the square of the
velocity created by that difference.

Though the weight of solid matter per
cubic foot of water carried near the bot-
tom is often but little more than near the
surface, it is commonly much coarser,
and therefore uses up much more trans-
porting capacity. The velocity near the
bottom is also less. From each of these
circumstances, especially from both to-
gether, it follows that the transporting
capacity is much greater near the bottom,
where the boiling motion is greatest, and
where the difference in the velocity of the
films of water is the greatest, than near
the surface.

It is sometimes said that the trans-
porting capacity with any given velocity
is inversely as the depth. This cannot
be so, for it would lead to the absurd
conclusion that, with the same velocity,
a stream a foot deep is capable of carry-
ing as much silt in the aggregate as a
stream a hundred feet deep.

If a stream runs over a soft uniform
bed for a sufficient length of time, it
will become charged with the maximum
quantity of solid matter due to its
velocity, its depth, its boil, and to the
size, shape and specific gravity of the
particles taken up by its current. If
there is not suitable material within
reach of its current, it will carry less
than its maximum. As before pointed
out, aggregate weight of silt alone is a
very imperfect measure of transporting
capacity. The maximum load with the
same velocity may perhaps be two orv
three times as great with one material as
with another.

If a stream carrying its maximum
quantity of silt widens as you go down
stream, so that, when the water is high,
its section becomes greater than that of
the stream above, the velocity decreases
there, and a deposit takes place. The
coarsest particles will drop first, and
thus the bar formed is likely to be hard.
When the water subsides, so that the
area over the bar becomes less than that
of the deeper water up-stream, the de-
clivity of the surface must be increased
in order to get the increased velocity

130

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

necessary to pass the water through the
smaller area, and that raises the surface
above the bar, deadens the current up-
stream, and causes a deposit to take
place in the deeper water above. Thus
the tendency of expansions of a stream
beyond its normal width is to raise its
bottom not only there but everywhere,
and consequently to increase the height
of its floods.

If, on the other hand, a wider place is
contracted to the normal width of the
stream, the velocity will be increased so
as to cut out the bar, if the material of
which it is composed is not too hard. By
making the channel of uniform width,
and keeping it regular and even, the bed,
if soft, will be lowered, and the height of
floods diminished. With a given dis-
charge, the greater the depth, the less
the fall required ; or, with the same fall,
a less area. A memorable example of
the deepening effect of the contraction
of a stream to the regular width is by
the South Pass Jetties.

The tendency of the greater velocity
to take up and carry off solid material
is illustrated at bends of rivers. The
swiftest water is near the concave shore,
that side of the channel is in conse-
quence deepened, and the more rapid
current eats into that shore. The cur-
rent on the convex side is slackened and
a deposit takes place. Hence a crooked
stream has a constant tendency to be-
come more crooked.

It has always been a wonder why an
eddy current was more erosive than a
direct current. My theory is, that when
the water turns from its direct course
and curves round towards the shore, the
centrifugal force separates and throws
off a a part of the coarser particles held
in suspension (just as in old times when
a farmer threw a shovelful of mixed
wheat and chaff, the heavier wheat went
beyond the chaff), and thus the current
being now deprived of a part of its load,
its power of erosion is partially restored,
and it cuts the bank rapidly.

The Mississippi River approximates
the conditions of such a stream as I
have described.

The first thing done to improve it is
to make its channel as uniform as pos-
sible by contracting its wide expanses.
This is done by placing a continuous line
of brush mattresses or screens along

each boundary of the modified channel,
the edge of the mattress next the channel
being sunk to the bottom with stone,
the edge farthest from the channel being
buoyed up to the surface of the water.
The silt-bearing water filters slowly
through the mattress, and the current
being deadened, drops its sediment and
soon forms a sediment under and behind
the mattress. This new bank is pro-
tected from erosion by the inclined face
of the mattress. In floods the current
goes over the mattresses into the
bays outside, where the velocity being
slackened the silt is deposited, the bays
are gradually filled up, and dry land
ultimately forms between the line of the
mattresses and the original shore. Con-
fining the current increases the velocity
and deepens the channel between the
lines of the mattresses, a uniform chan-
nel is established, the bed of the stream
is lowered, the water being deeper less
declivity of surface is required, the water
surface is lowered, and the overflow in
floods moderated.

When running water washes the foot
of a vertical bank, suppose for example
60 feet high, and washes out a narrow
groove along its face, suppose a foot
deep, and then the overhanging mass
falls so as to leave the bank still vertical,
the quantity that falls into the stream is
60 cubic feet per foot lineal of the
stream. The finer part of this will be
carried* down stream, the coarser will
probably gradually work down to the
bottom and raise the bed. Thus the
capacity of the river will be diminished
and the height of the surface and of the
floods increased. But if the water of
the same stream washes a foot horizon-
tally into a bank sloped one to one, and
the overhanging weight falls so as to
leave the back of the step thus made
vertical, the quantity thus thrown into
the stream will be only half a cubic foot
per foot lineal.

Hence the absolute necessity of slop-
ing the banks of the Mississippi where
they are steep and unprotected. The
commission are forming this slope by
the use of the water jet, and protecting
it until the rootlets and willows cover
and protect it, by a slight covering of
brush.

The great forces of nature, though
they cannot be resisted, may often be

KNiilNKKKING : PA8T AM) PRESENT.

i:*l

glided and controlled by means that
seem the feeblest. The magician of
science is to control the mighty Missis-
sippi with the willow wand.

If a stream of uniform section, bear-
ing its maximum load of silt, and con-
rfna? within its banks, is furnished with
ad additional channel, then though each
channel may take its proportion of the
silt brought down from above, the re-
duction of velocity consequent on the in-
creased aggregate sectional area, will cause
a deposit to take place below the bifur-
cation, the bed of the original channel
will be raised and its capacity diminished.
Hence a bar is likely to form below an
extensive crevasse.

But if a stream overliow its banks,
then the water that would otherwise
run overland may be carried off by ad-
ditional outlets, so that that they do not
lessen the velocity of the main stream,
below the point of diversion.

The principles that govern such cases
are mostly plain enough, but owing to
many disturbing circumstances, their
application is often very difficult. A
thousand cases may arise where oppos-
ing tendencies operate, each tendency
with imperfectly known force, about
which no man can form an intelligent
opinion without an intimate knowledge
and careful study of the circumstances,
and careful weighing of the force of the i
opposing tendencies.

I have stated those principles and
their application, not because hydraulic
engineers will find anything new in the
statement, but to bring them to the at-
tention of such dry land engineers as \
may not already have considered them.

I think no apology necessary for j
dwelling so long on this subject, for j
there is no other so opportune, no other I
more important.

To this generation it seems almost
ridiculous to mention turnpikes as ever ,
having been of any interest. And yet
the city of Philadelphia retained for a
time its commercial ascendency by them,
especially by the great Lancaster turn-
pike. If I rightly remember the Ian- 1
guage of the geography I studied when
a boy, it somewhat exultingly described
this turnpike as " seventy-two miles |
long, four rods wide, and covered, wide
enough for two wagons to pass, with j
eighteen inches of pounded stone." It)

was over this highway that the wealth
of the interior poured into the commer-
cial metropolis of America, in Conestoga
wagons.

The national roads from Washington
and Baltimore into Ohio, made by the
Federal Government, are famous for
their share in settling some of the im-
portant constitutional questions of our

1 government. One great party disputed
the power of Congress to use the
nation's money for any such purpose.
The contest was long and fierce, but
Congress, with much misgiving, made

; the appropriations. When a few years
ago they appropriated $15,000 for the
improvement of the Kiskiminitas, they
must have got bravely over such mis-

! giving.

Though canal engineering is a thing
of the past, its history is instructive. In
England it commenced 120 years ago,
the first engineer being James Brindley,
a millwright. He seems to have known
little of what had been done before, and
his plans were evidently original. When
he proposed to build an aqueduct across
the Irwell for the Duke of Bridge-
water's canal, his critics said they had
often heard of castles in the air, but
they never heard before where they were
to be put. Brindley built several canals,
on one of which was a tunnel a mile and
a third in length.

He was succeeded in canal making by
such men as Telford and Smeaton and
Bennie. Though uneducated, he gained
the admiration of scientific as well as
practical men. When he wished to study
a subject thoroughly, he " laid in bed to
contrive," as he expressed it. The secret
of his success, therefore, evidently lay in
concentration of attention on the subject
in hand, and he kept out of the way of
anything that could distract his atten-
tion.

The era of canal building in England
was rather less than seventy years ;
between 1760 and 1830.

During the last decade of the last
century, several efforts were made to
connect the detached navigable reaches
of some of the rivers in this country,
by means of short canals and locks. One
of these was undertaken at Richmond
under the inspiration of General Wash-
ington. Another was at Philadelphia,
around the Falls of the Schuylkill. But

132

VAN NOSTRAND'S ENGINEERING MAGAZINE.

the one of special interest in the history
of engineering, was at Little Falls on
the Mohawk.

The great thoroughfares between the
City of New York and the West and
Northwest was up the Hudson and
through the valley of the Mohawk. The
transportation through that valley was
partly by three, five, or seven-horse
teams over the Genesee Turnpike,* and
partly by boats on the river. Those
boats were like what on the Delaware we
used to call Durham boats, which were
8 feet wide and 60 feet long, drawing,
when loaded, a foot or two, and carrying
from 10 to 20 tons. They were pushed,
up stream by two or four men, with set-
ting poles held against the shoulder,
and kept on their course Jay the captain
with a long steering oar.

At Little Falls the descent of the river
is over forty feet, and, of course, the
boats could not pass, but their cargo
was carried by the portage of two miles,
to other boats above or below. To avoid
this the canal and locks were built.
They were finished in 1794. Jedediah
Morse (father of S. F. B. Morse, of tele-
graphic fame) published lys great stand-
ard American Gazetter a few years later,
and in it he quotes the following expres-
sion of the public sentiment of the time :
" The opening of this navigation is avast
acquisition to the commerce of this
State." It was conjectured that these
locks (which a man could almost jump
across), and similar " great works " west
of them, might soon make the little town
of Albany the capital of a great empire.

The Mohawk continued to be the prin-
cipal artery of commerce from New York
to the interior, until the opening of the
Erie Canal in 1825.

Mr. Weston, " that haughty British
engineer," as an old gazetteer calls him,
was brought over from England to build
the locks at Little Falls and elsewhere.
One of his assistants was a land surveyor
of Borne, New Yoak, named Benjamin
Wright, or Judge Wright, as he was
called. When, years afterwards, it was
decided to build the Erie Canal, Judge

* The migration to the West, (which then meant the
Genesee country; was over tbis turnpike in horses or
ox teams ; the patriarch of the family and his wife
having on their shoulders the same black and white
coverlet, and the big brass kettle full of dishes hang-
ing under the hinder axletree of the wagon. Some of
their grandchildren now sit in the high places of the
nation.

Wright, though having only the slender
experience he had acquired under Wes-
ton, was appointed chief engineer. The
skill and good judgment which was
shown by this father of American engi-
neering, the few errors into which he
and his still more inexperienced assist-
ants fell, the great effects produced by
them with the means at their command,
and the adaptation of their works to the
circumstances of the time, are absolutely
wonderful.

One of Judge Wright's principal as-
sistants was Canvass White. His skill
early brought him into notice, and he
was sent by the State of New York to
England to learn what he could, espec-
ially about hydraulic cement. Despair-
ing of getting it at any reasonable price,
and of making it stand the voyage, then
from four to ten weeks, he set himself on
his return to finding or making a substi-
tute for European cement.

: Led partially by the geological posi-
tion of the hydraulic limes in England,
and partly by what was known of their
composition, he explored and tested cer-
tain rocks of Western New York, and
made the first discovery of hydraulic
cement in America. The State of New
York gave him ten thousand dollars for
his discovery. Subsequently he discov-
ered or recognized cement rock in Penn-
sylvania in the way till then unknown,
but now so familiar, by the contact of
limestone and slate.

And yet how soon those men, once so
widely known, are forgotten. An emi-
nent and excellent engineer, who had
paid especial attention to cement, lately
told me he never heard of Canvass
White.

One of Judge Wright's assistants, but
much younger than Canvass White, was
John B. Jervis, whose name to-day is
one of the most honored on the rolls of
this society.

Many of the distinctive characteristics
of American engineering originated with
those Erie Canal engineers. We prac-
tice their methods to-day, though most
of their very names are forgotten. As a
class, they wrote little. There were then
no engineering papers prepared, and no
engineering societies to perpetuate them,
if they had been prepared. They were
not scientific men, but knew by intuition
what other men knew by calculation.

engineering: past and imiksknt.

133

Judge Wright's counsel was *' as if a
man had inquired at the oracle of God."
What science they had, they knew well
how to apply to the best advantage.
Pel? men have ever accomplished so
much with so little means.

The mention of cement reminds us of
quite a new use of it, lately, under the
direction of Mr. Chanute. The Erie
road crosses the Genesee River by a
high viaduct just above a fall. The bed
of the river was wearing away, and would
soon destroy the viaduct. An artificial
bottom of cement has stopped the wear.

The Erie Canal was opened in 1825.
Gov. Clinton passed through in a boat on
one corner of the deck of which stood a
cask of water from Lake Erie, on another
corner a cask of water of the Hudson.
Gov. Clinton limped from the boat to the
public halls, and speeches were made by
and to him : and it was a great glorifica-
tion. The result justified the public ex-
pectation. It built up the City of New
York, and settled the question of com-
mercial supremacy between that city and
Philadelphia.*

The success of the Erie Canal soon
brought about the construction of many
others. They were thought to afford
the most economical means of transpor-
tation, and railroads were made, not to
carry goods to the final destination, but
to a canal or other navigation. After
the success of the Liverpool and Man-
chester Railway in 1830, this opinion
was seriously shaken, and in a short time
canal construction mostly ceased. Its
era in this country was scarcely a quar-
ter of a century, between 1817 and 1835.

Canals to be successful now must be
capable of passing vessels of large ca-
pacity, must not have too much lockage,
and the locks must be worked by steam
or water power ; the boats must be
moved by steam, either on board, when
the vessels are large enough, or, when
the vessels are smaller, by locomotive on
the bank, or by cable at the bottom, and
then the locks must be large enough to
hold the fleet taken by one locomotive or
cable tower ; there must be plenty of
water, and the canal must connect har-
bors or navigable waters.

I tried towing by locomotive on the

* An old pilot once told me that in his youngrer
days there were three or four ships out of Phila-
delphia to one out of New York.

canal bank more than forty years ago.
There is, of course, no difficulty in one
engine towing several boats, but if the
locks are not large enough to piss the
whole fleet at once, the delay of all the
fleet till each boat is passed separately,
counterbalances the economy of steam
instead of horse power. The speed even
for light boats cannot be increased to

i more than five or six miles per hour on
account of the wave.

Cable towing, notwithstanding the re-
ported failure on the Erie Canal, can,
with proper boats and apparatus, and
with experienced men, be easily per-

! formed on the crookedewt canal in Amer-

; ica, as it is now done in Belgium.

Canal engineering does not avail itself
of the engineering resources of the age.
Little improvement is made in it : main-
ly, I suppose, because it is not consid-
ered worth improving.

The most remarkable early river im-
provement in this country was that of
the Lehigh.

About the year 1817, Josiah White
and Erskine Hazard commenced the im-
provement of this river, and made other
preparations to inaugurate the anthra-
cite coal trade. In 1820 they sent to
market 365 tons, which was the begin-
ning of the regular anthracite coal trade

j of America. Now the annual amount

\ will soon reach 30,000,000 of tons.

The descending navigation they made

j consisted, first, in clearing the channel
of rocks, and confining the water in the

! rapids,1 when low, to that narrow chan-
nel by boulder wing dams; second,

j when the fall was too great for this, in
building dams with bear trap locks ; and
third, in storing the water in pools, and
letting it run only when the coal arks

! were running.

The bear- trap locks have given the
hint for several devices since used, and
are well worthy of examination. Near
each end of the lock was a pair of gates,
each gate reaching across the lock and
to the back of the recess on each side,
which gates, when not damming back
the water, lay flat on the bottom of the
lock. The lower gate could be made to
revolve through an arc of somewhere
about 40 degrees around a horizontal
axis coincident with its down-stream
edge. The upper gate of the pair, when
laid flat, lapped over about half of the

134

VAN NOSTKAND'S ENGINEERING MAGAZINE.

width of the lower gate, and revolved
through a similar arc around its up-
stream edge. When laid flat, the water,
of course, ran freely over them. They
were raised by admitting the water un-
der them from the pool above the head
of the lock, through the side wall, when
the pressure of water pressed them up.
They were prevented from going too far
by shoulders in the recesses. The gates
then came within 10 or 15 degrees of be-
ing at right angles to each other, the un-
der side of the upstream gate resting on
the upstream edge of the downstream
gate. They could be held in any posi-
tion, so as to hold back the water entire-
ly, or let it run over with more or less
volume, as required. The arks contain-
ing the coal were commonly shot through
over the partly raised gates as over so
many dams.

Such locks, copied from those on the
Lehigh, are now in use on the Ottawa,
at the Canadian capital. Many of us at
our last convention were shot through
them on rafts.

It is well worth inquiry whether these
bear-trap gates would not be the best
possible, and possibly the#cheapest, for
letting the water rapidly out of a reser-
voir for scouring purposes. A full
stream could be set running in a few
seconds, and the flow could be regulated
with perfect ease, and stopped at any
moment.

In many rivers it is desirable to dam
the stream back at low water, and let it
run freely at high water. In Belgium,
on the Meuse, they use needle dams for
this purpose. Another probably better
adjustable dam is in use in France.
The bear trap gates, with proper appli-
ances, on a solid platform at the bottom
of a river, would enable a man on shore
to raise a dam across that river, or if
raised, to lower it to the bottom, in a
few minutes.

I have used this contrivance for a fish
sluice in a permanent dam, by which the
water ran freely through the sluices when
necessary, and at other times was re-
tained at full height.

The coal, on the descending navigation
of the Lehigh, was sent to market in arks
consisting of six boxes, 16 feet square
and 20 inches deep, coupled by hinges,
the whole carrying about 100 tons.

Of course, it often happened in that

hazardous navigation that the arks were
wrecked. The lumps of hard coal were
soon rolled down-stream by the current
to some shoal below, where they were
found in the form of completely rounded
boulders.

In making these improvements,, eight
hundred men were employed at once near
Mauch Chunk, then in the wilderness,
quite outside of the bounds of civilization.
It was not easy to control these men,
many of whom, doubtless, had never been
remarkable for good order. The sheriff
of the county was unable to make an ar-
rest. But the fertile genius of Josiah
White, and the strong good sense of
Erskine Hazard, soon found a remedy.
Under their inspiration the men organ-
ized themselves into a republic, adopted
a code of laws, which their backwoods
poet put into rhyme, and these laws,
which they themselves had made, were
strictly enforced and universally submit-
ted to. Punishment was inflicted by a
good stout hickory stick, as big as your
finger, well laid on with a strong arm.

The chief executive of this republic,
called the lieutenant, was also the exe-
cutioner. When all hands were called to
witness punishment, they said or sang the
part of the law which had been trans-
gressed, and the lieutenant beat time on
the offender's back. One of the gravest
offenses was for a man to take more on
his plate, or his shingle, than he could
eat. Punishment of this soon stopped
the grabbing, and the provision bills
were very much reduced. At any official
announcement, the expression of loyalty
to the supreme authority, was not as in
England, " God save the King," or as in
Pennsylvania, "God save the Common-
wealth," but " Hurrah for Mr. White and
all the rest ! "

Engineers and employees may well
take a hint from this piece of history.

Josiah White, the Pennsylvania Archi-
medes,-as he was sometimes called, in-
vented, among many other things, the
drop gate so valuable, in canal locks of
moderate rise. In 1827, he and Hazard
built the Mauch Chunk Railroad, nine
miles long, the first railroad (except a
little tram road at Quincy granite quar-
ries) ever built in America. My hap was
to ride on it within a few weeks after it
was opened.

In the early times of the coal business.

ENGINEERING : PAST AND PRESENT.

135

the same coal passed in succession
through several hands, each of whom had
an interest distinct from the rest. The
owner of the land, tbe mine operator, the
owner of the lateral road to the canal, the
canal company, the boatman, the tide
water vessel owner, and the coal mer-
chant, must each make a profit, or he
would stop, and that would stop all the
rest, though, taken altogether, the profits
made by some would greatly counter-
balance the losses made by others.
Hence, those parties who performed all
the operations, succeeded best, for they
always kept on and made something,
while those who took the different steps of
the business in succession were stopped,
because some of them made nothing.
Thus, the latter were driven to consoli-
date, though often against their earlier
intentions. The owners of coal roads
bought large tracts of coal land, not to
monopolize, but to insure a constant
stream of transportation, at times when
private owners are accustomed to stop,
because there is no profit in their branch.

This generation wonders how the busi-
ness of the world ever could be carried
on, and especially, how railroads ever
could be run, without the telegraph.
And yet many of us remember when
there was none. And after it was shown
that information could be sent by an
electric current through a wire, it was
years before any one made use of it.

About fifty years ago, Professor Henry
made a series of brilliant discoveries in
electro magnetism, one of which was, that
by means of a current through a wire, a
signal could be made and information
given (by ringing a bell, for example),
a long distance off. Years afterwards,
Steinheil, Morse, Wheatstone and others,
applied Henry's discovery to the actual
conveyance of information ; Morse's ap-
paratus, as it seems to us Americans,
being by far the best. The wonder to us
now is, why Henry himself did not apply
his discovery, and why others did not
sooner do so. The answer is found in a
very important phase of human mind.
The habit of mind into which the scien-
tist is liable, perhaps likely, to fall, is to
look at scientific result as his ultimate
end. Such result arrived at, the same
habit of mind is to use it only to attain
further scientific result. Hence, men of
science so rarely are benefited pecuniarily

by fcjeir own researches. Hence, also, it
frequently happens that engineers who
have kept at their studies without prac-
tice till too late in life, are so often less
successful than those of far less science,
and, perhaps, less intellect, but who have
been early trained to apply to practical
use what science they have.

Iron ship building has had almost its
entire growth within the last forty
• years.

In the spring of 1845, I visited a small
iron ship yard, then quite a new thing,
at Birkenhead, on the south side of the
Mersey. The proprietor, in his green
flannel roundabout, showed his modest
establishment, and explained some of the
processes. That proprietor became after-
wards well known to the world as Sir
John Laird, the great iron ship builder,
and especially to this country as the
builder of the Alabama. The operations
of that enterprising craft came near in-
volving us and our cousins across the
water in a very serious conflict. This
was averted by the moral courage and
enlightened patriotism of Grant and
Hamilton Fish on this side, and Glad-
stone and Clarendon on the other, who,
not having the fear of demagogues be-
fore their eyes, agreed upon arbitration
instead of war. All honor to the states-
men who took this great step in Christian
civilization.

They were just beginning to build the
first dock wall on the red sandstone bed
rock of the Mersey ; now they have 159
acres of dock room enclosed. Then
Birkenhead was a small village ; now it
has more than 100,000 inhabitants.

America is not the only country that
moves.

Mr. Chanute, in his annual address,
two years ago, spoke of the first pro-
peller boat used in America. That pro-
peller fell into my hands ; and I towed
the first fleet of boats ever towed by a
propeller tug on this side of the Atlantic,
from Philadelphia to Bordentown, in
October, 1839. Now, our harbors are
full of them. The first propellers ever
built in this country, and, as far as I
know, the first iron hulls, were the
Anthracite and the Black Diamond,
built on the Plans of Captain Ericsson,
and employed in carrying coal through
the Delaware and Raritan Canal. The
first sea-going propeller built in this

136

VAN NOSTRAND'S ENGINEERING MAGAZINE.

country was the frigate Princeton, built
on Captain Ericsson's designs, under the
direction of Captaiu Stockton. It was a
full rigged sailing ship, the intention
being to use steam only as auxiliary.

It should not be forgotten that John
Stevens, almost eighty years ago, built a
small propeller boat, with two propell-
ers, or " circular sculls," as he called them,
and ran it about the harbor of New York.
It is wonderful how near his blades ap-
proach the angle which experience has
shown to be best. He used a small loco-
motive boiler, as it would now be called,
such as was reinvented by Booth, a
quarter of a century later, at Liver-
pool.

The rapid progress of the country,
and the activity of the age, are more
strikingly shown by the records of the
Post Office Department, than by the in-
crease of population — from three to fifty
millions since the revolution — or than by
any other statistics I know of. During
several years of the time that Benjamin
Franklin was Postmaster General, he
personally kept' the whole accounts of
the department, and all in one small
book, and settled with, the postmasters '
and mail carriers. There were then about,
perhaps, twenty or thirty dead letters a
year, now there are four millions. It
now takes eight clerks constantly em-
ployed to open them, and I remember
that it takes fifty clerks to take charge
of one class of them. Franklin kept
one small book, which lasted three years,
now there are 150 or 200 books, each
half a dozen times as large, filled each
year. Then the work was done by
Franklin for $600 a year, now by 700
clerks, for, perhaps, a million a year.

Within my memory, some of the sci-
ences with which engineers have speci-
ally to do, have grown from infancy into
at least adolescence.

For example, geology was a collection
of interesting but isolated facts, and un-
verified theories, now it is a science. It
used to be considered terribly hetero-
dox, and a young man who cared to
stand well with good people found it
safest to say nothing about it. To read
geology was next to reading Tom Paine.
A learned and excellent divine once
confidently informed me that all the
supposed plants and animals found in
the rocks were merely stones that hap-

pened to come out in that shape. Now
geology has an important connection
with the instruction in theological sem-
inaries.

Business and population depend on
geology. A geological map of England
enables one to locate its occupations and
the denser populations. An outcrop of
gneiss, extending southwest from New
York, forms the limit of tide in the
rivers, and fixes the location of Trenton,
Philadelphia, Wilmington, Baltimore,
Georgetown, Richmond and other cities
to the southwest.

When I studied chemistry at school,
the components of compound bodies
were given in percentages. For ex-
ample, limestone was 48 per cent, oxy-
gen, 1 2 per cent, carbon and 40 per cent,
calcium. Of course, nobody could re-
member such proportions. Nor did it
give the proximate elements of the com-
pound. The automatic theory, as it was
called, was known, but chemists were
cautious about accepting it. They had
not yet learned to distinguish between
the theory of atoms, and the fact of
equivalents.

One of the most surprising feats of
modern science is seen in the daily
predictions we have of the morrow's
weather. Time was, and many of us re-
member back to it, when predictions
were made, and by intelligent people,
too, from the phases of the moon, from
weather breeders, from the weather on
certain anniversaries, and the like.

More than a century ago Franklin
pointed out the fact that northeast
storms begin at the southwest, two or
three days earlier at New Orleans than
at Philadelphia. Much information was
afterwards accumulated, and scientific
investigations were from time to time
made by many able men. About forty
years ago Prof. Espy of Philadelphia
announced his theory, that rain is caused
by the rarefaction and consequent upper
movement of the mixed air and vapor
into a colder region, where the vapor is
condensed and falls into rain, and that
this rarefaction produced by the heated
surface of the earth, or by fire or other-
wise, causes the denser air to flow in
from every side, so that the wind blows
toward the rain. All this has been since
verified. But this sanguine philosopher
did not get the credit he really deserved,

engineering: past and present.

but drew upon himself the ridicule of
the world, by claiming for his discovery
more than it could accomplish, especially
by proposing to raise the Mississippi
by Betting lire to the woods on the
Allegheny mountains, when the hygro-
meter showed much moisture, and so
getting the upward current required to
make it rain, just as it commonly rains
after any great fire, or the eruption of
a volcano, or a battle.

Espy visited Princeton to confer with
Prof. Henry. I was present at the in-
terview. Henry, while he thought
Epsy's main principle quite correct,
got very much out of patience with him
for several hasty conclusions from state-
ments which, to Henry's cautious,
scientific mind, did not seem at all con-
clusive.* After he was gone, Henry
chalked out the plan which he after-
wards, with the co-operation of Guyot
and other able men, so successfully car-
ried into execution, of simultaneous ob-
servations all over the country, and a
daily chart of highest and lowest pres-
sures, and other things about which my
memory is less distinct. As everybody
knows now, it is the traveling of these
lines from west to east, at an average of
about thirty miles an hour, that enables
the weather predictions to be made.

Our rapid progress involves the fre-
quent undoing of what has only recently
been done in the most costly manner.
We have seen expensive buildings erected
in the city of New York, and then in
two or three years torn down to give
way to something greater or different.
The Allegheny Portage Railroad, of
which my brother, Sylvester Welch, was
chief engineer, W. Milnor Roberts being
one of his assistants, was considered
for some years one of the wonders of
the world ; the improvements in the
locomotive and the increased strength
of the rails afterwards enabled engines
to cross the Allegheny without the in-
clined planes used on that road, and
that splendid work, on which so much
thought had been expended, was torn

* My attention was drawn to this subject by the
conference between Espy and Henry, and while
traveling in Ireland, I asked my very bright, and on
the subjects within his range, intelligent car driver,
which way the storms there came from ? Evidently
he had never thought on that subject, but, adopting
on the instant a meteorological creed, answered quicE
as thought : " The storms, sir, come from whichever
way the Lord Almighty chooses to send them."

Vol. XXVII.— No. 2—10.

up. It is folly to build for the far
future.

This reminds me that in a paper writ-
ten in 1829, read before this society
two or three years ago, Mr. Moneure
Robinson estimated that the tonnage
over the Allegheny mountain at that
point might in time reach 30,000 tons
per annum. I suppose that the tonnage
now over the mountain, on the Pennsyl-
vania railroad, exceeds six millions.

One of the bold and remarkable works
of the day is the submarine sewer at
Boston, to carry the sewage under an
arm of the harbor and across an island
far to seaward. They have discovered,
what unfortunately many others have
not, that little is gained by emptying
sewage into a harbor or into a small
river, and so transferring the nuisance
from one point to another, or distribut-
ing it all over.

Sanitary engineers have been contend-
ing each for his own favorite system of
sewering and draining cities. Mr.
Hering, in his paper read at the con-
vention at Montreal, impressed upon
us that no one system is absolutely good
or bad, but either is good when adapted
to the circumstances, and bad when it is
not. Municipal corporations often think
that the remedy for unhealthiness is, of
course, sewerage, just as some doctors
in old times gave their patients calomel
without regard to what was the matter
with them, or what kind of constitutions
they had.

One of the startling propositions of
the day is to bring the waters of Lake
George and the upper Hudson by an
open canal to supply the city of New
York. When somebody asked Brindley
what rivers were made for, he said: "To
feed navigable canals." The answer
now would be : " To supply great cities
with water."

Among the subjects to which the at-
tention of the society is now especially
turned are Standard Time and the Preser-
vation of Timber. As wre expect reports
on these, I shall not further refer to them.

One of the most remarkable of modern
implements, one whose powers seem al-
most miraculous, is the diamond drill,
which bores into the hardest quartz con-
glomerate and even into chilled iron. It
seems to be capable of much wider ap-
plication than it has yet had.

138

VAN nostrand's engineering magazine.

The attachment of a car to a moving
wire rope, in the way proposed by Col.
Paine, without injury to the rope or risk
to the car, will probably revolutionize
the mode of traction in very many cases.

Within the last year or two the load
on each wheel of a freight car has been
increased from 5,000 lbs. to 8,000 lbs.,
an increase of 60 per cent. According
to Dr. Dudley's observations on the
Pennsylvania Bailroad, an increase of 60
per cent, on a wheel made an increase in
wear per million of tons of a little over
30 per cent. We may expect that this
recent increase will increase the wear at
least 30 per cent. ; that is, the rails on a
heavy traffic road that would have lasted
with the old machinery 10 years, will now
last 7.7 years. But with the heavier
weight on a wheel, the residuary part of
the rail after it is worn down to the limit
of safety, must be much stronger than
formerly required, in order to bear the
heavier weight. Suppose the diminution
of the consumable part of the rail on this
account to be 20 per cent, (which would
be only 4 or 5 per cent, increase on the
whole rail) it reduces the duration to
6.16 years with the same traffic. But as
the traffic has increased much more rap-
idly than was expected, it is now proba-
ble that the rails on our heavy traffic
roads will not last half as long as they
were expected to last three or four years
ago. If a rail will last a dozen years
where actually used, it would not pay to
add more than about thirty per cent, to
its cost to make it last two dozen years,
but it would pay to add 45 per cent, to
its cost to prevent its duration from com-
ing down from a dozen to half a dozen
years. Steel rails were made fifteen years
ago with twice the endurance of those
made now. Under the new circum-
stances, it is probable that it will before
long be economy for roads with the
heaviest traffic to pay the railmakers a
price that will enable them to make rails
as durable as the best ever made.

The concert of action among so many
persons, and over so great distances, es-
sential to the safe, efficient and economi-
cal operation of our railroads, and, there-
fore, to the safety and cheap accommoda-
tion of the public, makes it necessary
that all the operations of a great system
should be in one interest and directed by
one central authority. These might be

governmental, but in our country, at
least, experience has shown that this is
absolutely inadmissible. It is in the
hands of great corporations, who have
vast amounts of property and armies of
men under their control. In some places
every third man you meet wears the but-
ton of a corporation. Whether this con-
centration of power is is itself good or
evil, it is inevitable ; and certainly a less
evil than its alternative. The possession
of this power carries with it grave respon-
sibilities, especially in promoting the wel-
fare of their employees.

Many of the best and wisest corpora-
tions recognize the duty of regarding
their employees not merely as parts of a
vast machine, but also as men. Saying
nothing now of any higher considera-
tions, they know that if they show a
proper interest in their employees, their
employees will feel more interest in
them ; that if they provide a comfortable
retreat for their train men when off duty
they will not be driven to the liquor
saloon for shelter ; that if they give
facilities for intellectual and moral im-
provement to the men off duty they will
be better, and especially more reliable
employees ; and that if they give them
the day of rest which God and human
experience have alike declared to be neces-
sary, they will be more efficient.

Time was when corporations had very
limited powers. Now they can do pretty
much everything an individual can do,
and a great deal besides. So officers
could do little without specific authority
from the directors. According to my
recollection of the minute book of the
company, which in 1804 built the cele-
brated bridge across the Delaware at
Trenton, at a cost of $180,000 (a great
sum at that time), the very first resolu-
tion of the board authorized the presi-
dent to purchase two shovels and a crow-
bar.

The subject of uniform time for rail-
roads is now claiming the special atten-
tion of this Society. It is of great im-
portance, but it has been so recently and
so fully placed before the Society by Mr.
Fleming and others that it is only neces-
sary to call attention to their communica-
tions.

The subject of tests for large members

of metallic structures is now receiving

I our earnest attention. If I should speak

ENGINEERING : PAST AND PRESENT.

189

of its necessity it would only be to repeat
what is said in our memorial to Congress.
I will only again call attention to one
point ; that is, that the process of manu-
facture of a large piece of iron or steel
may be so different from that of a small
piece, and therefore the quality of the
two be so different, though both may be
made from the same stock, that the
strength of the larger cannot be infer-
red, but only guessed at, from the
known strength of the smaller. In the
larger there is more likely to be perma-
nent opposing strains that destroy a
large percentage of its strength. A re-
markable instance of opposing strains,
caused by treatment in manufacture,
was pointed out some time ago by Col-
onel Paine. He found that wire coiled
before it was set could not be even
straightened without straining the sides
beyond the limits of elasticity, and that
such wire had nothing near the strength
of that ceiled stright. As the strength
of a large metallic member of a structure
cannot be tested by any machine within
the reach of individual means, and as to
obtain the best results requires the com-
bined skill of several classes of experts,
the aid of Congress is invoked to provide
a suitable machine, and to create a board
of experts whose varied skill shall plan
the best experiments.

We are justly proud in this country of
the system of checking baggage on our
railroads. A traveler gets a check for
his trunk at a hotel in Philadelphia, and
gives himself no further trouble about it
till he finds it at his destination, perhaps
in Maine or Texas, or Oregon. It con-
trasts favorably with the system on the
Continent of Europe, and especially
with the want of system in England.
But our hadling of baggage in
this country is shocking. A light
English trunk will travel all over
Europe without injury. Here it is
likely to be destroyed in a single trip.
The greater weight of the stronger
trunks required here costs the railroad
companies quite an appreciable amount
in the course of a year, and the dam-
age to the trunk and its contents by
the rough handling it gets sometimes
costs the passenger as much as his
fare. And in the great majority of
cases careful handling would not cost
anything extra.

What is, and is to be, the effect of all
the activity and progress of the present
day on human welfare ?

Doubtless the preponderance of effect
is good, but with many drawbacks. I
will notice one :

The rapid movement of the business
of the world requires an immense amount
of brain work to be done by those who
direct it in each business day. This is
made possible by the recently introduced
facilities for rapid work. Formerly,
when a man wrote his own letters, he
thought sentences only as fast as he
could write them. Now he dictates
three or four sentences to his stenog-
rapher in the time he would have been
writing one, and so performs three or
four times as much brain work per min-
ute, as he would if the wrote himself.
He does not go out of his office to 'con-
fer with a man at some other office, but
sits still and telephones him. When the
railroad officer travels on his own road
he does not chat with his friends in the
public car, but goes in his office car,
with his stenographer, clerks and table
covered with papers. When a man goes
home from his office he does not take the
time to walk, but works on till the last
moment, then goes on the Elevated Rail-
road. The brain gets no rest, as it
would have got in old times ; now con-
stantly rushing forward, not standing in
its tracks, as formerly, while the man was
writing down the thought of the pre-
vious instant; now furiously at work,
while formerly resting while the man
was going from place to place. This
kept up for six or eight hours a day
must soon break a man down, and has
already broken down some of our ablest
men. It does not mend the matter
much that next summer he can spend a
few weeks at the shore, or among the
moimtains. A man running up hill till
he is out of breath is not enabled to keep
on running another hour by the prospect
of rest next week. A man that runs a
locomotive twenty miles an hour may
run all day, but if he runs sixty miles
per hour, and so his brain and eye have
three times as much to do per hour, he
must soon stop to rest.

Undoubtedly the progress of the age,
which is so largely engineering progress,
does on the whole greatly increase the
welfare of mankind. By making the

140

VAN nostkand's engineering magazine.

forces of nature do the hard work, the
labors of the toiling millions are light-
ened many fold. The laboring man now
works with brain and eye more than
with muscle, and his business is now to
apply some principle of science. This
raises him intellectually. He now has
time for improvement. Comfort and re-
finement, and even luxury, are brought
within his reach. The forces of nature
having become obedient to the will of
man, they are made to produce for him
not only plenty, but conveniences and
luxuries formerly undreamt of. By the

present facilities the races of men are
brought into contact with each other.
Those races are being assimilated, and
the prejudices and hatreds of the past
are fading away. Supreme power among
men is more than ever in the hands of
the most enlightened, and they are send-
ing civilization and Christianity into the
regions most benighted. The light of
Heaven is beginning to shine into the
Harem and the Zenana. And the time
seems to be hastening when there shall
universally prevail " peace on earth " and
"good will towards men."

WIND PRESSURE.

By WILLIAM FERREL.

Written for Van Nostrand's Engineering Magazine.

In the January No. of the Engineek-
ing Magazine, p. 49, is an article, copied
from 2he Architect, in which is con-
tained a theoretical formula on the
pressure of the wind which makes it
twice as much as it should be. The im-
portance, often in engineering, of hav-
ing an estimate of the possible amount
of wind pressure, renders it important
that we should have correct theories and
formulae upon the subject. Let

U, V=linear co-ordinates respectively
perpendicular to, and parallel in
any direction with, the earth's sur-
face ;
w, v=the corresponding velocities re-
spectively in these directions ;
&=the density of the air ;
^=fche acceleration of gravity.

We then have the well-known equa-
tions

-9-

'kd\J~~dt~

dP ddY

■ (1).

kdY dt J

For our purpose it is only necessary
to solve these equations in the special
and simple case of horizontal motions, in
which case we can assume k to be a con-
stant, and u — o. From the last of these
equations we get in this case

dP dY ddY

vdv

k dt dt
and by integration,

F0-?=ik(v*-v\) . . . (2).
in which P0 is the value of P where v

—v(

With u=o, the second member of the
first of (1) vanishes and we have by in-
tegration

0*=Xj=w

(3).

in which, since we have assumed that k
is constant, U is the height of a homo-
geneous atmosphere of the pressure P,
and hence

to = the weight of a unit of volume of air
of tension P.

From (2) and (3) we therefore get

v2-v\

Po-P

2<7

-w

(*>•

Where the wind is stopped by a per-
pendicular barrier we have v0 =o, and
then have, putting p=V0 — P

P=Sj»

(5).

In this expression p is the increase of
pressure at the surface of the barrier over
the general pressure P, and hence it is
pressure of the wind, and vanishes when

WIND PRESSURE.

141

v vanishes. This expression makes the
value of p only half as much as the form-
ula referred to above.

The weight of a cubic foot of water at
temperature of 4=° C, which is the tem-
perature of maximum density, is 62.431
pounds avoirdupoise, and the density of
dry pure air at sea level, on the parallel
of 45°, under a barometric' pressure of
760m"\ and having a temperature of 0°
C, according to Regnault, is .00129278.
And according to the laws of Marreotte
and Gay-Lussac, the weight of a given
volume of air is as the pressure and in-
versely as the absolute temperature.
Hence we have

w=62.431.

.00129278 P_
1 + .003665*'F

.08072 P

1+.003665*'P'

in which P'=760mm P is the baromet-
ric pressure of the air under considera-
tion, and * is the temperature according
to the French scale. With this value of
to (5) becomes, putting g = 32.17 feet

.001255 P .

1 + .003665* P

(6).

in which p is the pressure on a square
foot, in pounds avoirdupois, and v is the
velocity of the wind in feet per second.

At or near sea level, P : P' can be as-
sumed, generally, to be equal unity with-
out much error. At the top of Pike's
Peak or Mont Blanc it would be about
one-half of unity, and hence at these al-
titudes the pressure of the wind for the
same velocity is reduced about one-half.
It is seen that an increase of tern
perature also decreases the pressure of
the wind, but this, in ordinary variations
of temperature, does not amount to very
much, so that if the numerical coefficient
is adapted to some average temperature,
the temperature may be neglected with
out much error.

Where v is expressed in miles per hour
the formula becomes

For what barometric pressure and -tem-
perature is not stated.

Hagen's empirical formula, deter-
mined from very accurate experiments
only a few years ago, is

p= (0.00707 + .00011^5?0*V . . . (9).

in which p is expressed in grams, u is
the periphery of the plate and F the sur-
face of the plate in decimeters, and v is
the velocity per second in decimeters.
The barometric pressure in the experi-
ments was 758mm and the temperature
15° C.

This formula, with p expressed in
pounds avoirdupois, u and F in feet, and
v in miles per hour, becomes, when ex-
pressed so as to include variations of
pressure and temperature,

p= (0.003064 + .0001191 u)^

Fv5

.002700 P

1 + .003665* P

i>y

(7).

The following is Smeaton and Rouse's
empirical formula, which is usually found
in text books and manuals,

£> = .00492v5

(8).

P'l + .003665*

. . . (10).

It is seen that this empirical formula,
in all cases, gives a pressure considerably
greater than the theoretical formula (7),
but much less than that of (8), unless we
suppose the periphery of the plate u to
be large. Hagen's experiments were
made with small plates varying from two
to six inches square. How nearly the
formula would hold for much larger
plates, remains to be determined from
experiment.

The value of p, given by the theoreti-
cal formula (7), is the true increase of
pressure on the side of the plate ex-
posed perpendicularly to the direction of
the wind, and would be the effective
pressure of the wind in overcoming ob-
stacles opposed to it, if the pressure were
not diminished on the side opposite to
that exposed to the wind.

The air, in passing around any barrier,
diminishes the pressure on the opposite
side, mostly by dragging the air away in
passing, through the effect of friction
between different strata or portions hav-
ing different velocities. This is seen in
the effect of hoods placed on the tops of
flues of chimneys to prevent their smok-
ing. The air is dragged away and the
pressure diminished so that the air
escapes from the flue more readily.

If we put

p=the diminution of pressure on the
opposite side of the barrier,

142

VAN NOSTKAND'S ENGINEERING MAGAZINE.

we shall then have p +p' for the effec-
tive pressure of the wind, snch as is ob-
tained by experiment. Deducting (7)
from (10), putting F=l, we shall have,
according to Hagen's experiments,

(11).

,_/. 000364 +.0001191iAP 2

^~V 1 + .003665* /FU

as the effect on the opposite side due to
the dragging effect of the wind. It is by
the amount of this term that the empiri-
cal formula should differ from the theo-
retical. It is seen that this part increases
by Hagen's formula, with the increase of
the periphery of the plate, and hence with
the size of the plate used in experiments,
and with only a moderate increase in the
size of the plates, this part of the effect-
ive pressure would exceed the other part,
and in case of a large barrier, as the side
of a house, it would be very much
greater than the other. But from ex-
periments made through so small a
range, we cannot infer that this would
be the case, and we are left very much
in doubt as to what it would be, except
for the small range, for which experi-
ments have been made,, but we at least
know that in all cases the value of p can-
not vanish, and that the effective press-
ure of the wind must be considerably
greater than the theoretical pressure
given by (7).

In Gehler's Physicalisches Worter-
buch, Vol. X., Part II., p. 2076, we find
the following ratios between the theoret-
ical and experimental wind pressures :
Marriotte, 1 to 1.73 ; De Borda, 1 to
1.66; Bouse, 1 to 1.90; Hutton, 1 to
1.243 ; Woltman, 1 to 1.19 ; of these, it
is stated, the last one is considered the
most reliable, and those of Rouse and
Marriotte the least. Bejectingthe latter,
and giving to Woltman twice as much
weight as to Hutton and De Borda, we
get the ratio 1 to 1.32. The ratio be-
tween (7) and (10), putting F = l in the
latter, is for a circular plate of an area
equal to one square foot, 1 to 1.256.
The differences between the preceding
ratios may have arisen from plates differ-
ing very much in size, having been used
in the different experiments.

Anemometers constructed upon the
wind-pressure principle are the most re-
liable, since they depend only in a small
measure upon friction, and the velocity is
determined mostly from the observed

pressure theoretically, leaving a com-
paratively small part of the formula, due
to friction mostly, to be determined by
experiment for the particular plate used
in the anemometer, and to be applied to
the theoretical formula in the form of
(11). Such anemometers are very sensi-
tive to very small changes in velocity
with short periods, such as those which
occur when the wind blows in gusts,
and observations made with such ane-
mometers are more useful to engineers
than those made with Bobinson's ane-
mometer, which leaves no record of the
maximum velocities of sudden gusts of
wind, which usually do the principal
damage.

Since by (7) pressures are as the
squares of the velocities, it is seen that
small changes in velocity produce a much
greater change in the pressure, when the
regular velocity is great than when it is
small. "With a wind blowing at the rate
of 50 miles per hour (7) gives a pressure
of 6.75 pounds on the square foot, but
with a velocity of 100 miles per hour it
gives four times as much, or 27 pounds
to the square foot.

The cause of the winds blowing in
blasts in a cyclone, is the small tornadoes
which are constantly being formed within
it. On the side of the tornado in which
the motion around its center coincides
with the direction of the wind in the cy-
clone, the velocity of the resultant wind
is the sum of the two, but on the
other side it is the difference of
the two. Hence when a tornado
within a cyclone passes over any
place, there is a certain sudden increase
of velocity or gust of wind, or there is
a momentary lull, according as the one
or the other side passes over the place.
If the central part passes over the place
there is not much change of velocity, but
a great change in the direction of the
wind causing a sudden oscillation in the
wind-vane. Small tornadoes or whirl-
winds are being continually formed
within cyclones, because the conditions
are then favorable for their formation,,
the air then being generally in a state of
unstable equilibrium and having a gyra-
tory motion.

If we express p in (7) in terms of the
height of the mercurial column in the
barometer, instead of pounds per square
foot, it will give the changes of the bar-

ill I : A.NALYSIR OF POTABLE WATEE,

143

ometer due to the wind. The atmos-
phere under a barometric pressure of
30 inches has a pressure upon the earth's
surface of '2116 pounds upon a square
foot. Hence, putting

b = t\w barometric pressure correspond-
ing to /), we have

.0027X30/- P

2116(1+. 003666V) P'

_. 00003827V2 JP_
~l + .0036G5r "T7

(12).

According to this formula, if the wind
blows perpendicularly against a wall or
any kind of barrier, with a velocity of 50
miles per hour at sea level and tempera-
ture 0° C, we shall have b = 0.0957, or
nearly one-tenth of an inch as the effect

upon the barometer placed close to the
wall where v = o. Hence, when the wind
blows by blasts a barometer so placed is
subject to numerous small oscillations,
called "pumping." This also occurs
when it is placed in a room into which
the wind blows, or presses through some
open door or window, and has no free
egress on the opposite side. There is
also some of this observed when the
barometer is placed on the opposite side
of a barrier, or in a room in which there
is a door or window on the lee side.
The effect is then produced, not by the
changes of pressure due to change of
velocity given by (7), but to the smaller
effects depending upon changes in the
value of p in (11).

Washington, June 20, 1882.

THE ANALYSIS OF POTABLE WATER, WITH SPECIAL

REFERENCE TO THE DETERMINATION OF THE

PREVIOUS SEWAGE CONTAMINATION.

By CHARLES WATSON FOLKARD, Associate Royal School of Mines.
From Proceedings of the Institution of Civil Engineers.

As far as the examination of mineral
substances is concerned, analytical chem-
istry is in a very advanced state. In-
deed, it may be a matter of opinion as to
whether any improvement is required
for practical purposes. But as regards
organic chemistry, especially that
branch which deals with the secretions
and tissues of plants and animals, the
reverse is the case, and analysts are at
present groping in the dark. Nor is this
to be wondered at, when the enormous
number, great complexity of composition,
and unstable nature of these bodies are
taken into account, and also the short
time that has elapsed since they were
first studied. It is a comparatively
simple matter to estimate the per-
centages of the constituents of a
body, in other words to make an ultimate
analysis of it ; and where one element
forms but a few combinations with an-
other, the relative amounts of the con-
stituents determine which of the com-
pounds is under investigation. But in-
asmuch as hundreds of organic com-

pounds are made up of the same three
or four elements, and in many even the
proportions of these elements are nearly
the same, it is obvious that ultimate
analysis will not afford sufficient informa-
tion to allow of the presence or absence
of a certain substance being predicated.
If the analyst receive the substance in a
pure state, or if it be capable of purifica.
tion by crystallization, distillation, &c,
its physical properties of specific gravity,
form, color, &c, are of great assistance
in ascertaining its identity. But if a
solution in water is the form in which it
is received, and especially if the solution
be very dilute, the difficulties are greatly
increased. When, in addition, the sub-
stance itself is very prone to decomposi-
tion, and is mixed with other bodies
equally unstable and equally hard to de-
tect, a degree of complexity is intro-
duced into the investigation which makes
it an almost hopeless task in the present
state of chemical science.

Such are the perplexities under which
the Water analyst labors, and their care-

144

VAN NOSTRAND'S ENGINEERING MAGAZINE.

ful consideration may serve to account
for the wide differences of opinion on
this important subject. It is much to
he regretted that this uncertainty should
exist, and it can only be hoped that in a
short time a bright light (possibly by
thetaid of electricity) will illumine this
almost untrodden ground of research.

The author proposes to divide the sub-
ject as follows :

1. The various ways in which water be-
comes contaminated.

2. The methods employed by analysts
to detect and determine the extent of
this contamination, with an opinion as to
the probable value of the results ob-
tained by the various methods.

3. The bearing of the results of biolog-
ical and microscopical research on the
question.

4. The adequacy or inadequacy of the
proposed remedial measures, irrigation,
chemical treatment, and nitration.

1. The various ways in which water
becomes contaminated.

Immediately on the condensation and
precipitation of the aqueous vapor of the
atmosphere as rain, the liquid dissolves
more or less of every substance with
which it comes in contact. Oxygen, ni-
trogen, carbonic acid, ammonia, and ni-
tric acid can be detected, and these may
be taken as normal constituents of rain
falling on the surface of the earth or on
the catchment reservoir of a town. It
will also be always more or less contam-
inated with the excreta of animals, al-
though reservoir water will contract but
an inappreciable amount of impurity
from this source.

The next stage for consideration is
rain water in the form of springs. In
addition to the above-mentioned bodies,
spring water contains various mineral
substances dissolved from the strata
through or over which it has passed, the
majority if not the whole of which are
innocuous in the quantities in which they
exist in most specimens ; together with
a further amount of animal contamina-
tion, varying in nature and quantity with
the character of the area, as to popula-
tion and agriculture, in which the springs
occur. In remote country districts the
contamination of the water up to this
point is very slight.

In the next stage, the rivers, there is
an enormous increase of contamination.

Nor is this to be wondered at, consider-
ing that rivers are the natural drains of
the country, into which every particle of
rain falling within their watersheds (ex-
cept that evaporated from the surface)
ultimately finds its way, with everything
which it is capable of dissolving or sus-
pending. Highly manured arable land,
pastures with their thousands of cattle
and sheep, mills, factories, village cess-
pools, and, lastly, town sewers, all con-
tribute their quota of foul water; in
some cases to such an extent that the
river becomes an open sewer in which no
fish can live, and the exhalations from
which, especially in hot climates, spread
fever and death around.

The remaining sources of water to be
considered are wells. In country places
these may be uncontaminated, but in
most cases it is far otherwise, owing to
the utter want of foresight in the sani-
tary arrangements, the cesspool being
frequently close to (and of course above
the level of the water in) the well. With
regard to wells in towns provided with a
deep sewerage system, they are generally
dry, fortunately for their owners ; on the
other hand, if the town be provided only
with cesspools, the ground is so satu-
rated with sewage matter from the latter
that the water is totally unfit for use.

2. Having thus considered the various
sources of water supply, and the nature
and amount of contamination to which
each is liable, the second division of the
subject follows — "the methods employed
by analysts to detect and determine the
extent of the contamination."

The mineral constituents may at once
be dismissed, as their determination is a
very simple matter ; and unless they ex-
ist in enormous excess, without doubt
they are practically harmless. The or-
ganic substances iu solution and suspen-
sion are the most important, on acconnt
of their dangerous nature, and, unfortu-
nately, they are the ones with which' the
chemist is least able to deal. As yet he
has been compelled to be content with
the examination and estimation of the
products of their decomposition — am-
monia and nitrous of nitric acids — or
with the determination of one or two of
their constitutional elements (carbon and
nitrogen). Urine per se is by no means
a difficult substance to detect and ana-
lize ; but the examination of water con-

THE ANALYSIS OF POTABLE WATEE.

145

taining one-hundredth or one-thousandth
part of urine, a week or two old, is a very
different matter. So also with the solid
excreta of animals on the one hand, and
the same suspended in minute quantities
in water on the other. In the present
state of analytical chemistry ir is impos-
sible to detect either the one or the
other in those highly diluted forms.
Common salt is abundant in urine, but
so it is in many soils, and therefore is
generally found in water ; and as it is
impossible to distinguish between that
derived from the land and the same sub-
stance contained in sewage, the fact of
its presence or absence in a sample of
water is not of much importance.

Then, again, rain contains ammonia
and nitric acid (if not also nitrous acid),
and it becomes impracticable to detect
whether these substances, when found in
water, are derived from the decomposition
of organic matter with which the water
has been contaminated, or have simply
been dissolved from the atmosphere by
the rain in falling.

(a) The oldest process for the investi-
gation of the organic matter in potable
water is by the incineration of the solid
mass left on evaporation of the sample,
and it has the great advantage of sim-
plicity. A measured quantity having
been evaporated to dryness, the residual
solid matter is weighed and heated, finally
to bright redness. The evaporation is
usually conducted in a platinum dish in a
water-bath, by which means loss by ebu-
lition is avoided. The residue, after
weighing, is heated to redness in the
dish over a Bunsen flame. By this
process the organic matter is burnt
away, carbonic acid, nitrogen, &c, being
given off. At the same time any carbon-
ate of lime or magnesia is decomposed,
the carbonic acid being expelled. To
correct the error thus introduced, the
ignited mass is moistened with a solu-
tion of carbonate of ammonia, by which
means the quick-lime left again takes
up carbonic acid equal in amount
to that expelled. It was generally
assumed that the magnesia did the
same, but this is found not to be the
case. The excess of carbonate of am-
monia having been driven off by a gentle
heat, the dish, with its contents, is again
weighed, and the difference, amounting
usually to from 2 to 6 grains per gallon,

was assumed to represent the quantity of
organic matter present. Unfortunately,
many water residues show a gain of
weight by this treatment, and it has been
conclusively proved that it is impossible
to measure the quantity of organic mat-
ter by this method ; but as it affords use-
ful hints as to its nature, it cannot well
be dispensed with. For instance, if, on
heating, the dry residue blackens, and an
offensive smell (especially one of burnt
hair) is given off, the existence of nitro-
genous animal substances in the water is
conclusive, and in nine cases out of ten
these substances are animal excreta of
recent origin. If, on the other hand,
there be little or no liberation of carbon
(and consequent blackening when the
water residue is heated), and if sparks be
noticed, or the peculiar smell of burning
touch -paper be perceived, organic matter
and nitrates or nitrites are indicated, by
the mutual reactions of which, at high
temperatures, these effects are produced.
From this it can be inferred that part of
the organic matter has been oxidized and
converted into the harmless salts of nitric
or nitrous acid, while another portion
remains undestroyed in the water.

Again, if the blackening produced by
ignition speedily disappear by contact
with the air, the organic substance from
which the carbon was liberated was most
probably of vegetable origin, and there-
fore less dangerous to the animal econ-
omy. If, on the other hand, the carbon
burns off very slowly, it was probably
derived from animal substances, which
are the most objectionable forms of or-
ganic impurities.

It will be as well to point out at once,
however, that there is a fundamental ob-
jection to the process in the very fact of
the evaporation of the water. There is
no evidence to show that such unstable
bodies are not partially, or in some cases
totally, destroyed during the process.
Indeed, with one of them (urea) this is
known to be the case.

(b) The process introduced by Drs.
Frankland and Armstrong is open to the
same objection, a prolonged evaporation
of the water, and although this is effected
at a temperature below the boiling point,
it is complicated, and in all probability
rendered far more destructive to the or-
ganic matter wnich it has been devised
to estimate, by the presence of mineral

146

VAN NOSTRAND'S ENGINEERING MAGAZINE.

acids during the evaporation. The resid
ual solid matter is submitted to ultimate
organic analysis, by which the amount of
nitrogen and carbon is computed. The
process is as follows : The water residue
is intimately mixed with oxide of copper,
and transferred to a tube, ^-inch in
diameter and 12 or 15 inches long, which
is then completely exhausted of air by a
Sprengel pump. The tube, with its con-
tents, is heated to bright redness, till no
more gas is evolved, and the products of
the reaction (consisting of steam, nitro-
gen, and carbonic acid) are pumped out
into a tube full of mercury standing in a
pneumatic trough. The steam is con-
densed, but the nitrogen and carbonic
acid are separated and measured, and
from the number of cubic inches of each
gas obtained, the weights of nitrogen and
of carbonic acid (and from that, of the
carbon itself) are easily deduced. • At a
red heat, oxide of copper decomposes all
organic substances, animal or vegetable,
transforming their carbon into carbonic
acid gas, and their hydrogen into aqueous
vapor, while the nitrogen is liberated in
the free state, also as gas. The presence
of mineral acid during t^e evaporation is
necessary to drive off the carbonic acid,
usually a carbonate of lime or magnesia,
which, if it were not previously got rid
of, would be expelled by the red heat
and mix with the carbonic acid formed
from the organic matter, so causing an
error. The nitrogen and carbonic acid
collected are measured over mercury;
the carbonic acid is then absorbed by a
solution of potash, and the gas left, which
is nitrogen, is measured, the difference
being the carbonic acid.

Having thus obtained the weights of
carbon and of nitrogen existing as or-
ganic matter in a certain volume of the
water, or rather that portion of the
organic matter which has not been de-
composed by the prolonged heating with
mineral acid, the quality of the sample is
inferred from their amount, and from the
ratio which they bear to one another, it
being assumed that the greater the ratio
of nitrogen to carbon, the more highly
organized, and therefore the more dan-
gerous, is the organic impurity. A very
little thought, hovever, will suffice to
show that the information thus obtained
is only of the most general character.
Assuming, then, that a high ratio of

nitrogen to carbon is characteristic of
the organic matter in a dangerously pol-
luted water, if a further pollution by or-
ganic substances, in which the nitrogen-
carbon ratio is small, take place, the
doubly-fouled water would be returned
as the less dangerous. This example
shows the weak point of the process, or
rather of the deductions made from the
data furnished by it, namely, the applica-
tion to a mixture of substances (the or-
ganic impurities of water) of reasoning
which can, properly speaking, only be
applied to the case of a single substance.

(q) A process which has found much
favor amongst analytical chemists is the
so-called albumenoid ammonia method.
It is assumed that the nitrogenous or-
ganic impurities in water are the most
dangerous, which is probably the case,
and the process professes to estimate the
quantity of these substances, by deter-
mining the amount of ammonia produced
by their decomposition when boiled with
an alkaline solution of permanganate of
potash. A glass retort and Liebig's con-
denser are used, the amount of ammonia
formed being estimated in the distillate.
This is effected by making up solutions
of ammonia of different known strengths,
and observing which of them gives a
brown coloration of the same intensity
as the sample under trial, when mixed
with a solution of iodide of mercury and
potassium.

No previous evaporation of the water
is necessary, which is undoubtedly a great
advantage over the first two processes ;
but inasmuch as this method is only an
imperfect ultimate analysis, even less
knowledge is obtained than by the second
method, though this has the great ad-
vantages of ease of manipulation and
rapidity, the results being in all proba-
bility of equal value for practical pur-
poses.

(d) The last to be considered is the
permanganate process, in which the
amount of permanganate of potash re-
quired to oxidize the organic matter is
ascertained. This is supposed to be an
index of the quantity of organic matter
in the water, and it would be so if only
one form were present ; but inasmuch as
there may be dozens of different sub-
stances in solution or suspension, some
hurtful, some harmless, some susceptible
of much oxidation, some almost, or even

THE ANALYSIS OF POTABLE WATER.

147

totally, unacted upon by permanganate
(and so far as is known the most danger-
ous may consume the least oxygen, or
none at all), it is obvious that this
method also will not afford results the
accuracy and reliability of which are
above suspicion.

The estimation of the ammonia, nitric,
and nitrous acids in water, is a simple
problem in mineral analysis, of which it
will be unnecessary to treat in detail.

Having briefly reviewed the advantages
and defects of the various processes for
estimating the nature and the amount of
the organic contaminations of potable
water, it seems impossible to come to any
other conclusion than that the subject is
as yet beyond the scope of analytical
chemistry. Even granting that the as-
sumptions of the advocates of the differ-
ent processes are correct, it is evident
that their deductions are illogical, reason-
ing fit for a single substance only being
applied to a mixture of substances.

As regards inorganic analysis the pro-
cesses can be checked by experimenting
on weighed quantities of pure substance
purposely mixed with other bodies. If
the same amount is recovered (within the
small limits of errors of experiment), the
process is evidently a reliable one ; but
with the impurities of water this is im-
possible, and the information afforded
by the methods now in use is of the
vaguest and most general character, so
far as the wholesomeness or the reverse
of a given sample is concerned, although
by one of them (b) it is possible to de-
termine the minimum amount of con-
tamination which has taken place since
the water was precipitated as rain. For
this purpose the whole of the nitrogen
existing in any form in the water is de-
termined, but this does not include free
or gaseous nitrogen dissolved from the
atmosphere, which is expelled in the pre-
liminary evaporation, and therefore does
not affect the results, viz. :

Nitrogen in the form of ammonia.

" organic matter.
" " nitric and nitrous acid.

Deducting from this total the average
amount of nitrogen in the form of am-
monia which exists in rain as it falls, the
residue is the minimum quantity which
the water has acquired from animal and
vegetable contamination. It is not neces-
sarily the total quantity acquired, because

some may have been abstracted by grow-
ing plants, &c.

No definite impression is conveyed to
the mind by the statement that there are
in a sample of water so many parts per
100,000 of nitrogen, derived from animal
and vegetable detritus. A standard of
contamination therefore becomes desira-
ble, and the one which has been proposed
is the amount of nitrogen per 100,000
parts of average filtered London sewage.
By simple proportion it is then easy to
calculate the degree of contamination of
any water ; that is as if 100,000 parts of
pure water had been mixed with so many
parts of London sewage.

It must be borne in mind, however,
that no distinction is made in this case
between nitrogen present as organic com-
pounds of more or less dangerous char-
acter, and nitrogen existing in the harm-
less inorganic salts of ammonia, nitrous
and nitric acids. This latter form of
nitrogen represents more or less original-
ly dangerous organic impurities, which
have been gradually resolved by oxidation
or fermentation into the inorganic forms.
Consequently a deep well-water, e.g. from
the Chalk, may be returned with perfect
accuracy as having received as much or
more " previous sewage contamination "
than a shallow well or river, and yet in
the former case the water may be abso-
lutely innocuous (all its organic impuri-
ties having been destroyed by oxidation
in the pores of the Chalk), whereas the
well or river water, with its recent con-
tamination, may be quite the reverse.

The first stage in the oxidation of
nitrogenous organic matter is the produc-
tion therefrom of ammonia, which by fur-
ther oxidation is converted into nitrous
or nitric acid.

3. Chemists being powerless to help
the sanitarian in discriminating between
wholesome and unwholesome water, it
seems essential to consider what can be
done by microscopists and biologists. In
the first place it is an ascertained fact,
proved beyond the possibility of doubt,
that mere dilution, how far soever it be
carried, does not render inoperative the
specific action of living germs, and so
marvelous is the rapidity of reproduc-
tion of low forms of life, that if the en-
vironment or conditions are favorable to
their growth, it matters little whether the
liquid is stocked with ten or with ten

148

VAN nostrand's engineering magazine.

thousand at the commencement. In a
few days there will be as many as can
exist, the only difference being that the
sample which received most of the con-
taminating liquid will arrive at the maxi-
mum a few hours before the other. There
can be little doubt but that the same
thing occurs in the case of the human
subject. Provided the individual is suffi-
ciently weakly or unhealthy, it is of small
importance whether he receive 1,000 or
1,000,000 parts of infectious matter
(whether in the form of organized germs
or not is immaterial), and consequently
1 part of infected sewage containing the
dejecta of persons suffering from zymotic
disease mixed with 1,000,000 parts of
water will be nearly as dangerous to him
as 1 part per 1,000. Of course the less
contaminated water would probably not
affect a person in more robust health who
might succumb to the use of the highly
contaminated sample ; but what the au-
thor wishes to insist upon is that it will
be impossible to banish zymotic disease
from a town whose water-supply has been
contaminated with the dejecta of patients
suffering from that disease. The very
weakly will contract it from the almost
inappreciable amount of infection con-
tained in the water, and from them it
will spread to those who have resisted
the poison in its diluted state.

Secondly, the germs which cause or
accompany disease are endowed with the
most persistent vitality, and are capable
of withstanding heat, cold, moisture,
drought, and even chemical agents, to a
marvelous extent. So difficult is it to
destroy them that for many years the
now exploded doctrine of spontaneous
generation found talented supporters,
who relied on their own carefully con-
ducted experiments to prove the theory,
all which experiments were subsequently
found to have been rendered illusory by
the astounding vitality of these low forms
of life.

Bearing in mind, then, the influence,
or rather the absence of appreciable in-
fluence, of mere dilution, and the diffi-
culty with which infectious matter is de-
stroyed, the conclusion that once con-
taminated water never purifies itself
sufficiently to be safe for dietetic pur-
poses becomes inevitable ; and as chemi-
cal analysis fails to give reliable evidence
as to its fitness or the reverse, the author

believes that the only safe test of the
wholesomeness of a given water is by
tracing it to its source, and ascertaining
that no objectionable impurities gain ac-
cess to it.

This will at once condemn all rivers
flowing through a populous country ;
and if it be considered that a river
is the natural drain of a district into
which everything soluble or suspen-
sible in water ultimately finds its vway,
it will not be a matter of wonder that
this should be the case. No Conser-
vancy Board can keep pollution out
of a river ; it must receive all the rain
falling within the limits of its watershed
(excepting, of course, that which is evap-
orated), together with the overflowings
of cesspools and the sewage of towns
within the same area. It is part of the
great circulatory system of the earth
which it is vain for man to attempt to
control.

This being so, it is evident that rivers,
except near their source, can only afford
polluted water, and a problem utterly in-
soluble by man is presented, viz., the
purification of foul water on a large
scale. The chemist can do it in the la-
boratory, but only by adopting a similar
process to that by which it is effected in
Nature — fixation of the ammonia in the
soil or its oxidation to nitric acid, fol-
lowed by distillation by the heat of the
sun. Take, for example, the case of a
river with a town of 50,000 inhabitants
on its banks. If supplied with Water at
high pressure and sewered, the amount
of foul water discharged into the river
will be about 1,000,000 gallons daily, ir-
respective of the rainfall, which will
bring with it the washings of the streets,
&c. Taking the total flow of the river at
500,000,000 gallons, and supposing that
the water is perfectly pure when it
reaches the town, there will be a mixture
of 1 part of sewage in 500 parts of clean
water, for the inhabitants of the next
town to drink. Take now an infected
liquid and add 1 part to 500 or even to
500,000 parts of liquid susceptible of in-
fection. The mixture will swarm with
low organisms and become putrid in a
few days, provided only the conditions
are favorable. And what may be ex-
pected to happen to the unfortunate in-
habitants of the lower town? Simply
this, that the strong and healthy will

null]

THE ANALYSIS OE POTABLE WATER.

149

have sufficient vitality to throw off the
poison, but the weak and sickly will suc-
cumb, inoculated by the dejecta of zymo-
tic patients in the upper town. Such a
state of things seems hardly possible in
a civilized community.

The above is no fanciful picture. The
experiment was tried on the inhabitants
of a town in Surrey, unwittingly it is
true, but on that account the result is all
the more reliable. An epidemic broke
out, and the consequent investigation re-
vealed the cause in all its loathsome de-
tails. Fortunately for mankind at large
the relation in this case between cause
and effect was distinctly traceable, but
in the great majority of cases this is out
of the question.

There is not the least evidence to show
that foul water is rendered wholesome
by flowing 50 or 100 miles; indeed, all ex-
periments point in the opposite direc-
tion, on account of the persistent vitality
of the organisms which accompany zymo-
tic disease, and of the utter failure of di-
lution to disarm these potent germs of
corruption and death.

4. The possibility of abating these
evils, otherwise than by a radical change,
will now be investigated.

It is often asserted that as the sew-
age of towns is " treated " by chemical
agents before being passed into the
river, the previous objections do not
hold good. But inasmuch as most of
the soluble matters are unaffected by
the process, and in view of the great vi-
tality of the low organisms, it is open to
doubt if the latter are destroyed by the
agents used. Even the irrigation pro-
cess, the most natural, simple, and effec-
tive where the locality is suitable, is lia-
ble to the serious objection that part of
the sewage may flow direct to the river
through accidental channels, without fil-
tration through the soil.

Putting, however, all this aside, those
who are practically acquainted with the
subject are perfectly aware that no sew-
erage system yet carried out (even
though its cost be reckoned by mil-
lions sterling) can cope with storm water.
As a necessary consequence the by-pass
must be opened, the sewage allowed to
flow direct into the stream, and the in-
habitants of the town below regaled with
a more than ordinarily filthy beverage
for the next few days. This again is no

fanciful statement; it can be seen in
operation more or less frequently all over
the country.

Filtration is another remedy put for-
ward as infallible by those who have not
grasped the subject. How can filtration
affect substances dissolved in water ? and
as for the minute organisms found in
putrescent bodies, they could pass a
hundred or a thousand abreast through
the interstitial spaces of ordinary sand,
as used for this purpose.

In the author's opinion, and probably

also in that of most people who have

carefully and dispassionately considered

the subject, the purification of diluted

sewage to a sufficient extent to render it

safe for dietetic purposes is an impossi-

' bility, putting sentiment aside alto-

; gether. Indeed, the mere idea of one

community drinking the diluted sewage

of another would be almost inconceiva-

I ble, were it not unfortunately a fret, and

; one with which the alarming increase of

cancerous diseases of the stomach and

intestines is in all probability, intimately

connected.

The present methods of water analysis
are quite capable of showing if contam-
! ination has taken place, at all events in
\ the majority of cases ; but as to whether
| that contamination is injurious to health
or not, there is no knowledge, and con-
| sequently the only safe course in the au-
I thor's opinion is to reject all sources of
supply unless they stand the test of ab-
solute freedom from organic substances
| so far as can be ascertained ; or prefer -
I ably, of rigid examination by tracing the
! water from the time it falls to the earth
i as rain till it enters the reservoir or well.

DISCUSSION.

Mr. Baldwin Latham said he con-
! curred with the author in the conclusion
that the chemist was not able to deter-
mine whether water was wholesome or
not. He used the word "wholesome,"
whereas the chemist used the word
" joure.'' The purity of the chemist
simply meant that he compared water
with a given standard, and if it came up
to that standard he said it was pure, and
if not it was impure. But the impure
water of the chemist was not always un-
I wholesome water, nor was the pure water
I of the chemist always wholesome. He
I differed from the author, however, in re-

150

VAN NOSTRAND S ENGINEERING MAGAZINK.

gard to some points, as, for instance,
that river exhalations were injurious,
spreading fever and death. Mr. Latham
maintained, on the contrary, that there
was no evidence to show that exhalations
from polluted rivers had proved to be
detrimental to health. Every authority
agreed upon the point that malaria was
never extricated from water surfaces, and
in malarious countries it was not until
the water bad disappeared that malaria
became manifest. In this country there
were sufficient examples to show that
the exhalations from foul rivers were not
unwholesome. He might instance the
case of the year 1858, before the sewage
was discharged lower down the Thames,
when the foul tide flowed through Lon-
don. It was a year of drought, and
great stench prevailed along the banks
of the river, but the mortality tables did
not indicate that the districts bordering
upon the Thames had in any way suf-
fered. He might quote other towns, like
Norwich, where the river Wensum was
formerly polluted in a similar way to the
Thames, thereby causing a great nuis-
ance to the villages below, yet not one
of them had suffered in health from the
exhalations. He could not agree with
the author that there was no evidence to
show that foul water was rendered
wholesome by flowing 50 or 100 miles,
and that dilute sewage (meaning, he pre-
sumed, water contaminated by sewage)
could never be made safe for dietetic
purposes. Nor could he agree with the
statement as to storm-water overflows,
but as that was no part of the question
under discussion he would not dwell
upon it. The subject of the paper was
one of considerable importance to those
engaged in questions of water-supply,
for he regarded the future improvement
of the sanitary condition of the country
as being almost entirely dependent upon
the attention which must be paid to
the selection of water -supplies, and the
means to be adopted for effecting the
purification of water. At present, if
engineers were to take the dictum of
some chemists, it was quite clear that
there was no water-supply fit for use.
In the sixth report of the Rivers Pollu-
tion Commission it was stated " that it is
in vain to look to the atmosphere for a
supply of water pare enough for dietetic
purposes." Now, as all sources of water-

supply were due to atmospheric causes,
and the author had stated that it was
useless to look for purification by any
mode which would be adopted by the
engineer, such as filtration or percola-
tion (because the germs, he said, could
pass a thousand abreast through a filter),
therefore if the rain-water was impure
as its source how could it ever be puri-
fied? Indeed, if the water-supply of
the country were in such a lamentable
condition, the wonder was that there was
any one living to describe the state of
things. The chemist could not discover
what were the dangerous impurities in
water. In order to supply a deficiency
in the paper, or the furnishing of facts
to substantiate the proposition put for-
ward, he would read an answer given to
a question by Dr. E. Frankland in the
Middlesborough water case. Q. 5,052.
" And do you think it most unsafe to
supply a large population from water
which has been impregnated with the
excreta of patients suffering from various
diseases'* I do ; although chemical an-
alysis may fail to detect anything un-
usual in the water, because I have my-
self mixed 1^ volume of the dejection of
a patient dying of cholera with 1,000
volumes of good water, and have sub-
mitted it to analysis, and have been un-
able to detect anything unusual in the
water ; chemical analysis is unable to
detect these small quantities of morbific
matter, which are calculated to transmit
disease to people drinking the water."
That was the opinion of one of the most
distinguished chemists of the day. "With
reference to the amount of contami-
nation in water capable of producing dis-
ease, he would quote from a little book
on "Portable Water," by Mr. Charles
Ekin, F.C.S. Mr. Ekin stated, p. 15,
" Waters which have undoubtedly given
rise to typhoid fever have been found
by the writer over and over again not
to contain more than 0.05 part of albu-
minoid ammonia in 1,000,000, and which
notwithstanding their containing a large
excess of nitrates have been passed by
analysts of undoubted ability as being fit
for drinking purposes." In an outbreak
of typhoid fever at Guilford in 1867, it
was clearly shown, on analyzing the water
which was the supposed cause of the
outbreak, that it was purer than other
samples on which no suspicion rested.

THE an \\.\ BI8 OF POTABLE WATER.

LSI

In all the calculations of the chemist it

appeared to be only a question of d< -
raid neither distinguish be-
tween the matters which were found in
tin- water, nor the source from which
f were derived. If a certain quantity
of organic mutter, whether sewage or
the "germs" of disease, was mixed in tin1
proportion of 1 part to 4 parts of pure
water the chemist would call the mixture
good water. On the 29th of November,
1875, when an epidemic of typhoid fever
was rife in Croydon, there were great

-picions respecting the quality of the
water supply. The level of the water in
the well at the waterworks was lowered
by pumping, and three samples of water
were collected as they trickled into the
well. They were submitted to Professor
Wanklyu, who gave the amount of albu-
minoid ammonia in the respective samples
as 0.14, 0.26, 0.22 per million parts. He
stated that two samples were highly
charged with sewage and that the other
sample was not pure ; but in the well
the water contained 0.04 of albuminoid
ammonia, and he added that that was
water of the purest class. Thus, from
the examination of the chemist, it ap-
peared that it was quite possible to mix
water which the chemist condemned as
impure with that which was pure, and
the result woald be that the water came
out as belonging to the purest class. As

the question of albuminoid ammonia
being the means of. showing whether
water was wholesome or not, he might
mention that about the end of the year
1880 the chairman of the Nantwich Local
Board of Health told him that the Medi-
cal Officer of health of Mid-Cheshire had
condemned the public water-supply of
the town as totally unfit for domestic
use. The supply was taken from a natu-
ral lake called i4 Baddiley Mere," and was
brought a distance of 4£ miles by gravi-
tation into the town. The authorities
had only power to draw off to a certain
depth the top-water. It appeared, from
an examination in October, 1880, that
the amount of free ammonia was 0.21,
and of albuminoid ammonia 0.44 in a
million parts in the unfiltered town water,
but after efficient filtration the amount
of free ammonia was 0.08, and of albu-
minoid ammonia 0.38. The chemist stated
in regard to it, " Organic matter in great
excess, rendering water dangerous and

unwholesome: the contamination not

recent ; filtration of little n In the

month of November a second analysis
was made, and the results were a Little
better. The filtered water showed ().:\'l
part <>f albuminoid ammonia instead of
0.38, and the remark by the chemist
was -kthe least said about these the
better." The report also contained the
analyses of the well-waters in use in the
town, which were, without exception, very
unsatisfactory from the chemist's point
of view. He then inquired of the Chair-
man of the Local Board what was the
state of health in the town ; he was in-
formed that it was never better, and he
therefore advised the Chairman of the
Board that as long as the public health
was so satisfactory to pay no attention
to the alarming reports of the chemist.
The Registrar-General had since issued
four quarterly reports on the health of
the district, namely, for the fourth
quarter of 1880 (embracing the period in
question), and three quarters in 1881.
During the year there had been one
death from scarlet fever, two from diar-
rhoea, and one from fever, the population
of the district at the census of 1881 being
11,192. The zymotic death rate in the
year was but 0.35 per thousand, or about
one-tenth the zymotic death rate of Lon-
don in the same period, and was one of
the lowest that it was possible to con-
ceive in any district, and yet the district
was supplied with " dangerous and un-
wholesome " water.

The following table showed the rela-
tive amount of average impurity in the
water supplies of London, as ascertained
by Dr. Frankland, together with the
death rates in each year. The investiga-
tion was begun in 1868, when the im-
purities in the Thames were called 1,000
parts. With that number the relative
amount of impurity in other years and
other sources of water supply was com-
pared. The numbers were proportional.

The highest annual death rate, and the
highest zymotic death rate in London
(1871) occurred when the impurities in
the Thames and Lee were below the
average, and the waters of the deep wells
were freest from impurities. The high
fever death rate in 1868 occurred when
the impurities in all the sources of water
supply were below the average. The low-
est death rate in London occurred in 1872,

152

van nostrand's engineering magazine.

Proportion of organic

impurity in Thames

water delivered

in London.

Proportion of organic
impurity present in

Lee water as
delivered in London.

Proportion of organic

impurity in deep

well water as

delivered in London.

CO _r

& ft
a p,

v ~

-p P
,_, O

* 5
a o

p^l

1868
1869
1870
1871

1872
1873

1874
1875
1876
1877
1878
1879
1880

1,000

1,016

795

928

1,243

917

933

1,030

903

907

1,056

1,175

1,263

484
618
550
604
819
693
583
751
562
596
747
954
1,143

254
312
246
150
221
250
287
250
246
243
323
387
393

23.5
24.6
24.1
24.7
21.4
22.4
22.4
23.5
22.0
21.5
23.0
22.7
21.6

Aver- )
ages, f

1,013

708

273

22.9

W TO r#>
%B?%
SgS

p —

0 ^ Tf,

9p-

©r

go'

5 £.2^

-^ p £>■
03 O N

4.82
5.57
5.19
5.97
3.84
3.32
3.29
3.87
3.56
.43
05
25
64

4.14

H-)ft

<V <0

co O

0.78
0.78
0.63
0.54
0.41
0.45
0.46
0.37
0.33
0.35
0.37
0.29
0.24

0.46

when the impurities in the Thames and
Lee were above the average ; and in 1880,
when the death rate was low, all . the
sources of water supply contained im-
purities in excess. The zymotic death
rate of London was lowest in 1879, when
all the sources of water supply contained
impurities above the average; and under
similar circumstances the fever death
rate in London was lowest in 1880. In
the year 1870 the waters of the Thames
and Lee contained the least amount of
impurity in all sources of water supply,
yet during the same period the death
rate had steadily declined. He did not
wish to impugn the character of the
chemists ; they were men of great hon-
esty and ability, and they themselves con-
fessed the things to which he had re-
ferred. Dr. Frankland had admitted
that small quantities of morbific matter
could not be detected by chemical an-
alysis. But there was a vast amount of
ignorance among the general public on
the subject, and he had himself to com-
bat it to a great extent in the case of in-
vestigations made at Croydon. Dr. M.
F. Anderson, in a letter to the Sanitary
Record of February 3d, 1877, stated, with
regard to the albuminoid ammonia pro-
cess, that he had " never been able to
obtain conclusive evidence that the dan-
gerous elements of bad water are evolved
as albuminoid ammonia ;" and he added,
" My observations tend rather to the be-
lief that typhoid germs are easily oxi-

dized, and do not yield up their nitrogen
as ammonia, but as nitro-oxides." That
rather went back to the question of
previous sewage contamination, which
seemed to be almost a phantom of the
past, as it appeared to have been aban-
doned by its author; but he thought
there was something in it, because it cer-
tainly showed the progressive impurities
that took place in water. From the
report of the Royal Commission on
"Water Supply, it was shown that in
the district from Caterham to Croydon
there was a very considrable increase
in the previous sewage contamination ; or
a progressive degree of deterioration in
the water had taken place. Those who
were conversant with the district would
know that there must have been such
deterioration because the valley was
thickly populated ; it had two water-
works in its upper part ; it had no sewers
whatever ; all the water pumped passed
through cesspools, and by a sort of circu-
lating system all the impurity was carried
back into the soil, and which flowed
down the valley, and what was not used
naturally found its outlet in the river
Wandle. It was evident that in a valley
of that kind there must be a natural
deterioration ; but unfortunately the
chemists had never been able to find it,
for although the previous sewage con-
tamination had enormously increased,
that counted for nothing with the chem-
ist at the present day. In such a dis-
trict, however, what might have been
proved to be serious sewage contamina-
tion was very likely to become present
sewage contamination of the most dan-
gerous description. In the epidemic of
fever in Croydon in 1875 the water had
been analyzed over and over again ; but
it was always pronounced to be water of
the purest class ; yet in that year one
person in forty- two living in the Croydon
water district suffered from typhoid fever
as against one in eight hundred and nine
in the district immediately outside, and
in many instances the same sewers were
used in common. Numerous investiga-
tions had taken place in connection with
the subject, and he had himself inquired
into it, feeling that it was an utter dis-
grace to the sanitary science of the day
that those repeated epidemics in Croydon
should escape detection. They had al-
ways been referred to the same cause —

THE ANALYSIS OF POTABLE WATEE.

L53

B6W6I gas : but he believed that he should
be able, from the facts he had collected,

to throw a very different light upon the
subject. If repeated coincidences were
tantamount to positive proof, he believed
he should be able to show that certain
meteorological conditions were connected
with the outbreak of every one of those
epidemics, which came into operation
only at particular times. One thing was
certain, that at all times the fever death-
rate in Croydon was inversely proppr- j
tionate to the quantity of water flowing
from the district. The author had stated
that it was necessary to trace water to j
its source. But that had been the diffi-
culty in Croydon. The late Dr. Letheby,
who analyzed the Croydon water, found
it to be good ; but that did not satisfy
his mind, for he distinctly reported to j
the authorities of the Friends' school, by ;
whom he had been called in, that the I
water-supply was dangerous by reason of
its source in the center of the town. Mr.
Latham at one period held the same
views as Dr. Buchanan, who reported on
this outbreak in 1876, that fever was
caused by sewer gas ; but he had seen
reason to alter his opinion. The diffi-
culty, however, had been to trace the
water ; but during the past year, not only
had the movement of the subsoil water
been traced, thanks to the ability of a
chemist in the city, but Mr. Latham had
been able to bring the matter under
direct calculation, and to show the quan-
tity of the immediate subsoil water get-
ting into the Croydon wells. The case
was this. The wells furnishing the sup-
ply of water to the town had been sunk
and bored into the porous soil, consisting
of gravel and chalk. They were lined
with iron cylinders for a certain distance
from the surface, and the subsoil water
outside the wells was supposed to be
shut out by the iron lining; yet when
pumping went on every fluctuation within
the wells was discernible in the subsoil
water outside. It had been stated by an
eminent engineer that these fluctuations
simply meant that there was a sympathy
between the waters. Other theories had
been advanced, one of which might be
called the " band-box " theory. It was
stated that when the water outside the
well subsided, it did not flow into the
well, but that it was like a tier of band-
boxes, the bottom one might be pulled
Vol. XXVII.— No. 1—11.

out, but the top one would not come
down. Then it had been referred t<> pul-
sations, or waves caused by the agitation

of pumping. Fortunately, for the sake
of science, on the occurrence of a bourne
flow at Croydon, early in 1881, he
ceived a communication from Mr. G. W.
Wigner, that if Mr. Latham would collect
the samples of water during the bonrne-
flow he would be happy to investigate
the matter from a chemical point of view.
After the collection of the samples, Mr.
Wigner wrote to him that it would be
desirable, as the next step, to trace the
movement of the underground water by
means of lithium. He saw at once that
this was exactly what was required to
ascertain whether or not there was a con-
nection between the immediate subsoil-
water outside the wells and the water
within the wells, and if the fluctuations
which had been observed were indicative
of this connection. Before making any
experiments, however, he put two ques-
tions to Mr. Wigner, one of which was
whether the material was innocuous, to
which the reply was, " perfectly innocu-
ous," and the other whether small quan-
tities of the material could be detected,
to which Mr. Wigner replied, " Yes,
3 ooVotT Pai't °^ a gram can be found in a
gallon of water by spectrum analysis, but
in no other way." Three experiments
were made at various distances from the
Croydon 'Water Works wells, and it had
been shown that the lithia moved in
all directions, exactly at the same rate,
into the wells, as the fluctuations in
the water caused by pumping had
been found to move. Lithia afforded,
therefore, a mode of readily detect-
ing the movement of water. It was
admitted that the subsoil-water at Croy-
don was in direct communication with
the sewers, and if it got into the wells,
it was a source of danger. There
were great difficulties in carrying out the
investigation, because the lithia could
only be detected by spectrum analysis.
Again, when material of that kind was
I put into the soil, a portion of it remained
j and was with difficulty got rid of, for
i when an acid salt had been put into a
I chalk soil, a portion of the acid combined
with the chalk, and a less soluble salt of
lithia remained in the soil. Investigations
of this kind should only be carried out
under the advice, and with the assistance

154

YAN nostba^d's engineeeing magazine.

of a chemist. He did not think that Na-
ture had left mankind in the unguarded
and unprotected state described by the
author, liable at any moment to have
their lives jeopardized from impurities in
water. There were means, no doubt, by
which the very foulest water could be
purified, and those means were more act-
ive in a river than in any other source
of water supply. He would refer to
the statement of Mr. T. Hawksley, Past-
President Inst. C.E., with reference to
the outbreak of cholera in 1848-9, re-
corded in the report of the Commission-
ers of Water Supply, that in those years
cholera was epidemic at Bilston, Wolver-
hampton, or in the Black Country; and
so violent was it that people encamped
outside the towns. During the whole
of that time the sewage of those infected
places flowed into the Tame, and, after a
course of 20 miles down the river, it was
used for the water supply of Birming-
ham, and there was no cholera in Bir-
mingham. It was therefore clearly
shown that by the simple flow of the
water that distance the morbific ele-

ments had been destroyed. He might
also refer to a more recent period, 1875-
76, when typhoid fever was prevalent
in Croydon, there being at least two
thousand cases in those two years, dur-
ing which time the whole of the sewage
of the town was passed on to the farm
at Beddington. There was a cluster of
eighty houses lying between the farm
and the Wandle, all inhabited, their only
water supply being from shallow wells,
and the proximity of the application of
the sewage upon the farm caused the
water in these wells to fluctuate, yet the
elements of disease were destroyed so
that there was not a single case of ty-
phoid in any one of those houses, or
even in the valley down to Merton, con-
taining a considerable number of inhabi-
tants. There again it was shown that
Nature had provided safeguards ; and it
was the duty of engineers to copy the
examples of Nature, and to treat water
in the way in which Nature treated it,
in order that the foulest and most dan-
gerous impurities might be destroyed or
removed from it.

ON THE PKOTECTION OF BUILDINGS FROM LIGHTNING.

By CAPTAIN J. T. BUCKNILL, R.E.
From the "Journal of the Royal United Service Institution."

A few weeks ago, when I accepted the
invitation of the Council of this Institu-
tion to read a paper on the application
of lightning conductors to buildings and
magazines, it never occurred to me how
difficult would be the task to deliver an
interesting paper on so special a subject,
or a paper that would be of value to a
purely naval and military institution. It
is, however, only too true that lightning
strikes soldiers, sailors, and civilian
alike, and that the laws which should
govern the application of conductors are
the same whether it be a palace or a jail,
a chimney, a cathedral, or a man-of-war
that has to be protected. Moreover, the
immense interests jeopardized by any
faulty arrangements, which might occa-
sion the explosion of magazines, makes
the subject of special importance to
naval and military men. Imagine the
loss to the war strength of the Empire

which would be entailed by the acci-
dental explosion of one of the large
magazines at Tipner or at Priddy's Hard,
with its charge of, say, 750 tons of gun-
powder, or over 750 millions of foot tons
of energy developed in less than one sec-
ond of time, and this within a short dis-
tance of the greatest naval arsenal in the
world, and a town with 120,000 inhabi-
tants. Every building shed would be
leveled to the ground, and the ^town
would be visited as was Chios the other
day. The proper application of light-
ning conductors to large magazines and
to men-of-war is evidently therefore a
matter of importance to us all.

Electricity exists in two distinct
forms, the static and dynamic, but the
word static thus applied is somewhat
misleading, because electricity (like heat)
is now recognized to be a form of mat-
ter in motion, whether in the state of

OS THE PROTECTION OP^ BUILDINGS FROM LIGHTNING.

L55

potentiality ;is in B thunder cloud, or in
the state of activity (the work-producing
state) as in lightning.

How the former is produced is still
conjectural, although a multitude of
theories have been propounded.

In whatever manner the electricity is
produced, the thunder clouds act as col-
lectors ; and more than this, when the
surface of the earth beneath them is not
far distant, and is composed of fairly
good conducting media, the earth, the
clouds, and the intervening air form huge
condensors — the electrified clouds acting
by induction upon the earth, and the lat-
ter reacting upon the cloud.

Now the amount of electricity of given
potential which a cloud is capable of re-
ceiving depends firstly upon its size, the
amount varying directly as the linear di-
mensions of the cloud ; and, secondly,
upon the intensity of inductive action of
the earth's surface, the cloud's power of
receiving electricity being greatly in-
creased thereby.

For example, a cloud of given dimen-
sions at an altitude of 300 feet could be
charged by 80 times the electricity that
would charge it were its altitude in-
creased to four sea miles.

For a similar reason a cloud over a
conducting area could be charged much
more highly than the same cloud at the
same height over a non-conducting area.

One of the most remarkable of the
phenomena connected with electricity is
the mutual attraction of bodies charged
with electricity of opposite sign, and the
mutual repulsion of bodies charged with
electricity of like sign. Now the charges
on inducing and induced surfaces are al-
ways of opposite sign. The bodies pos-
sessing these surfaces consequently at-
tract each other. If, therefore, thunder
clouds be driven by the wind or other-
wise over portions of the earth's surface
which vary considerably in their con-
ducting power, they will be attracted to
those regions which from their conduc-
tivity present the greatest facilities for
inductive action ; and this, in spite of
the mutual repulsion of the clouds ; just
as the numerous admirers of a beautiful
woman, although hating each other, are
attached to her.

Now it generally happens that the
thunder clouds in a storm are sufficiently
numerous to cover both favorable and

unfavorable areas of the earth's surface,
and, as little or no inductive action oc-
curs over the latter, but very consider-
able action over the former, the electro-
static capacities of the clouds become
greatly altered, and lightning plays from
cloud to cloud, until those which are
situated over the earth's conducting sur-
faces become so highly charged that the
electricities are able to overcome the re-
sistance of the intervening air and to
unite across it by what is termed the dis-
ruptive discharge. This is lightning.

I have been thus particular is describ-
ing the action produced by the earth's
surface upon thunder clouds, because
the somewhat important conclusion must
be arrived at, that lightning is most to
be feared by those who live on well-con-
ducting areas, even of low elevation ; and
that lightning is least to be feared by
those who live on non-conducting areas.
This is shown on plate, Fig. 9. where
the distribution of the electrical charge
is shaded in. The cloud over the Ports-
down Hill, although nearer to the ground,
is much less highly charged than the
cloud over Portsmouth and Spithead,
because the former presents a non-
conducting area. This electrical dis-
tribution is of .considerable impor-
tance, and it shows that it is much
more necessary to provide lightning con-
ductors for buildings situated upon a
damp clay or boggy bottom than for
those on a chalk down. This is very
convenient, for it is almost impossible to
make an efficient earth connection in the
latter situation.

As before stated, disruptive discharge
constitutes a lightning flash. Immedi-
ately before the stroke the particles of
air are subjected to a high strain by
static induction, producing a polar ten-
sion which is proportional to the square
of the potential. Faraday's experiments
proved this, as well as the fact that the
stroke tends to traverse the air in the
direction of such polarity. The tendency
of lightning is therefore to strike in a
direction normal to the earth's surface.

But there is another mode by which
thunder clouds are discharged, viz., by
the brush discharge.

Electricity of high potential leaks, as
it were, from conductors which are pro-
vided with projections in the nature of
points, where the distribution of electri-

156

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

cal density is greatest, a stream of elec-
trified air being thrown from each point,
and the charged conductor robbed by
continuous streams of its electricity in
this manner.

Although the brush discharge is fre-
quently so intense as to be luminous to
a height of 6 or 8 inches, it is not at-
tended with any appreciable heat. Its
action should therefore be fostered, as it
often wards off a dangerous stroke of
lightning by neutralizing the opposing
electricities in*a harmless manner.

It has been observed so late ago as
1758 by a Mr. Wilcke, that a thunder
cloud, in sweeping at low elevation over
a forest, not unfrequently appears to lose
charge without the occurrence of , light-
ning. The under surfaces of such clouds
at first present a serrated or tooth-like
appearance, which gradually disappears,
the teeth retreating into the cloud, and
finally the cloud itself rising away from
the forest.

In such cases the numerous points on
the branches of the trees present facili-
ties for the brush discharge on an ex-
tended scale.

To illustrate this action, an experiment
was made by Franklin, as follows : A very
fine lock of cotton was suspended from
the conductor of an electric machine by
a thread, and other locks were hung be-
low it ; on turning the machine the locks
of cotton spread forth their fine fila-
ments like the lower surface of the be-
fore mentioned thunder cloud ; on pre-
senting a point which was connected to
earth below them, they shrank back upon
each other, and finally upon the con-
ductor.

But to return to the lightning. Just
as a certain amount of water falling
through a difference of level produces a
definite amount of energy, so a certain
amount of electricity falling through a
difference of electrical potential pro-
duces a definite amount of energy. It is
known that if p be the potential and q
the quantity of electricity in a flash, the
work done during the stoke is \qp.
Now the duration of the illumination of
a stroke is rather less than the 10,000th
part of a second, and although q is small
(Faraday said not more than would de-
compose a single drop of water), p is so
enormous that the flash is often capable
of decomposing a million drops of water

in series. The potential can be calcu-
lated approximately, because it is known
that 10,000 volts will spark across a little
more than half an inch at ordinary at-
mospheric pressure ; and, as the spark-
ing distance varies as the square of the
potential, a flash of lightning 1,000 feet
long must be impelled by an electrical
potential of 1J millions of volts or there-
abouts. This is only approximately ac-
curate, because the mean atmospheric
pressure would be less than that at the
earth's surface, and therefore a correc-
tion should be made, as the pressure of
the atmosphere decreases very rapidly
with altitude, and the sparking distance
increases very rapidly with decrease of
atmospheric pressure. The work ^qp
done by a flash of lightning is used in
the disruption of the air, in the destruc-
tion of non-conducting solids that ob-
struct its path, in heat, in light, and in
chemical decomposition. Ozone is al-
ways produced during thunderstorms.

All that can be done to protect build-
ings from its destructive action is (first)
to attract the lightning to another spot
if possible, and (second) to arrange that
even if the building be struck, the work
shall be given out at other portions of
the path of the stroke. To do this it is
necessary to provide a sufficient conduct-
ing channel or channels to convey the
electricity past the buildings from the
air to the ground.

Firstly, let us examine the methods
which have been pursued for attracting
lightning away from the building which
it may be desired to protect. The French
Academie des Sciences has issued infor-
mation concerning lightning conductors
on different occasions, the several in-
structions having been the results of the
labors of various Commissions of cele-
brated physicists.

The first instruction, 1823, with Gay-
Lussac as reporter, the rule is laid down
that a conductor will effectually protect
a circular space whose radius is twice the
height of the rod, and it is stated to be
in accordance with calculations made by
M. Charles.

Accordingly we afterwards find in the
same instructions that magazines should
be protected in the manner shown on
Fig. 5, the wording being : " The con-
ductors should not be placed on the
magazines, but on poles at from 6 to 8

IMMMMM1

ON THE PROTECTION OF BUILDINGS FROM LIGHTNING.

lf)7

eet distance. The terminal rods should several conductors round each maga-
be about 7 feet long, and the poles be of zinc"

Flg.l.

Fig-. 7.

BUCKN ILLS ARRANGEMENT

FOR TESTING BY
WHEATSTONES BALANCE

PRESENT W.O. INSTRUCTIONS

ARRANGEMENT FOR MAIN MAGAZINE

[

Fig. 8.

THE POTTERIES

SHELTON CHURCH struck 1880. -

such a height that the rod may project | In 1854, however, the next Commission,
from 15 to 20 feet above the top of the , with M. Pouillet as reporter, no longer
building. It is also advisable to have ! supported this rule. The report says :

158

VAJST nostrand's engineeeino magazine.

' ' At the end of the last century it was a gen-
erally accepted opinion that the circle protected
by a conductor possessed a radius equal to
twice the height of the point. The Instruction
of 1829 (Gay-Lussac, rapporteur) having found
that practice established, adopted it with cer-
tain reservations. . . . These rules . . . rest
on much that is arbitrary." . . . "and they
cannot be laid down with any pretense to accu-
racy, since the extent of the area of protection
in each case is dependent on a multitude of
circumstances."

It is the more necessary to make this
quotation, because an attempt has recent-
ly been made by Mr. Preece to revive the
theory in a modified form. In a paper
which he read before the British Associa-
tion last year he attempted to prove
that —

' ' A lightning rod protects a conic space whose
height is the length of the rod, whose base is a cir-
cle having its radius equal to the height of the rod,
and whose side is the quadrant of a circle whose
radius is equal to the height of the rod. "

His argument was similar to, but not
of such general application, as that used
by M. Lacoine in a somewhat remarkable
paper read 20th June, 1879, before the
French Societe de Physique, from which
the following is extracted :

"Experience shows that a thunder bolt has
a tendency to fall on the metallic portions of a
building. If then, by the assistance of a light-
ning conductor we are enabled to protect a
certain metallic surface, much more therefore
will the same conductor protect the same sur-
face if non-metallic.

"Let N, Fig. 10, represent a thunder cloud
situated over the surface AC to be protected.
Assume that the cloud is at such a distance
from the point P of the lightning conductor
PO, that the circle described from N as center
with NP as radius will be tangential to the sur-
face AC. Then the cloud will be equally at-
tracted by the points P and E,* because these

* This is open to doubt ; the electrical charge on the
cloud is attracted by the induction of an opposing
surface, the total attraction being proportional to the
sum of the tubes of force existing between the two
opposing surfaces, charged by inductive action. To
assume that the charge on a tlmnder cloud is concen-
trated at a single point is not in accordance with the
circumstances of the case in nature.

Faraday's experiments have conclusively proved
that statio induction polarizes the particles or mole-
cules of the interposing di-electric, and that dynamio
currents tend to traverse the same by disruptive dis-
charge in the direction of the said polarity.

Assuming therefore that a lightning flash from the
charged surface NN' occur at N, it will have a ten-
dency to follow the direction NE rather than the alter-
native route NP, because polarity exists between NE
to a greater extent than between NP.

This consideration will cause the theoretical circle
of protection advocated by M. Lacoine to be consider-
ably diminished when the charged cloud lies low, but
when the cloud is at a considerable altitude NP be-
comes more nearly normal to the surface AC, and
more nearly parallel to the direction of polarity of the
atmospheric particles.

points are at the same potential, this rule hav-
ing always been admitted in all the instructions
of the Academie Francaise. Consequently
every point on the surface AC within the circle
with radius OE will be protected, but every
point outside E towards A would be unpro-
tected.

Fig. 10.

"Hence the radius of protection r =
VNE2-NB3,NE being the height of cloud
above the ground, NB being the height of
cloud above the conductor.

"It is enough, then, to know the height of
the thunder cloud, to know the radius of action
of a certain conductor.

" By several years' observation, and by direct
measurement, the average height of thunder
clouds could be obtained, and the mean value
o* r for any given conductor deduced there-
from."*

Mr. Preece does not work out any such
formula, but bases his rule on an assump-
tion that a thunder cloud would never be
nearer to the earth than the height of the
lightning rod. This is open to question,
as very low-lying thunder clouds may be
driven by the wind into the neighbor-
hood of lofty conductors that command
the clouds, and this is corroborated by
a case recorded in Mr. Anderson's excel-
lent book on lightning conductors, page
67, where the belfry of an edifice, 115
feet high, " remained standing out clear
above the electric cloud " whence issued
lightning that killed two priests near the
altar of the church. As a single applica-
tion Mr. Preece's rule comes at once
from M. Lacoine's formula.

It is perhaps important to bear in mind
these theories concerning the area of
protection given by conductors, when it
is necessary to fix a few conductors on
buildings of considerable extent, such as
barraeks, hospitals, &c, but sufficient re-
liance cannot be placed upon the rule to
enable us to consider the protection to

* As the height of thunder clouds varies enormously,
the values for r would range between proportionately
wide limits, and the mean value of r obtained by M.
Lacoine would seem to possess no definite or practical
utility. If, however, the observations were directed
to observing the minimum altitudes of thunder clouds
in each locality (the altitudes will be found to vary
with the locality), the smallest areas of protection
given to conductors there situated could be approxi-
mately established.

ON THE PBOTECTIOH OF BUILDINGS FEOM LIGHTNING.

158

magazines, us shown on Fig. 1. and
already alluded to, us efficient

The area of protection afforded by a
conductor depends much more upon the

efficiency of the earth connections than
upon the height of the tormina] point,
and in proof thereof many instances
might be cited. For example, in the

96 of Shelton Church, in the Potteries,
which was struck on thelOth June, 1880,
the tower, about 16 feet square, is sur-
rounded by four pinnacles 16 feet above
the roof, which is nearly tiat and covered
with slates, with lead guttering and
ridges. From the center of the roof
springs a large flagstaff, about 40 feet
high (see Fig. G), secured to the tower
in the upper chamber 20 feet below the
roof by large cross beams unconnected,
except by stone work, with the clock-
works, bells, and gas pipes in the cham-
bers of the tower. A copper wire rope £
inch diameter is fitted to one pinnacle
and taken direct to earth. Although the
flagstaff projects some 20 feet above the
conductor, and is distant only 10 feet, a
very heavy stroke of lightning, which
caused much alarm, and which was seen
to fall upon the tower, struck the con-
ductor, knocked the point slightly out of
the perpendicular, and passed off by it
innocuously. In this case a good con-
ductor, well connected to earth, protected
something higher than itself, but not
well connected to earth.

Again, Sir William Snow Harris men-
tions a chimney at Devonport which, al- j
though provided with a conductor, was
struck on the other side, and shattered
down to the level of a metal roof below. I
Here the conductor must have been
badly connected to earth, and was use-
less.

Moreover, the safe area rule may be
upset in practice by all sorts of acci-
dental circumstances. Thus, a house
within the theoretical circle of protec-
tion given by a church spire close at
hand might be struck if the line of least
resistance from cloud to earth were af-
forded by a column of rising smoke
from the kitchen fire, and the shorter of
the two chimneys in Fig. 6 would most
assuredly be struck, for a similar reason,
although it is within the theoretical cone
of safety of the taller chimney as fixed
by Mr. Preece.

In short, if thorough protection be de-

sired for any building it is necessary to
put a conductor or conductors upon it.*
Let us now examine the manner in
which conductors should be applied.

Churches and dwelling-houses of ordi-
nary dimensions, factory chimneys, monu-
mental columns, &C., need but one con-
ductor led from the most lofty point to
the ground, to which a thorough efficient
earth connection (to be described pres-
ently) must be given. As a rule it is
the best plan to fix the conductor ex-
ternally, in which case it should be con-
nected to all external metal surfaces,
but not to any masses of metal wholly
within the building. It should be fixed
to the exterior by strong clamps of iron
or other metal, and provision should be
made for its expansion and contraction
due to differences in temperature. It
should be continuous from top to toe.
It should possess a proper amount of
conducting power per unit of length.

As regards the last mentioned and
most important matter of conductivity,
the last French instructions, dated 14th
February, 1867, state that there is no
case on record where lightning has fused
a square bar of iron having a side of 0.6
inch, or a section of 0.36 []'' — and square
iron conductors 0.8-inch side are recom-
mended, which gives a section of 0.64 [~|".
Also Sir William Thomson considers
that a round iron bar 1" diameter would
form a very safe protection for maga-
zines; this would be about 0.77 []" sec-
tional area. It would appear that con-
tinuous iron conductors weighing 6 lbs.

* A lamentable result of the practice of placing
lightning conductors distant from a building occur-
red at Compton Lodge, in Jamaica, the residence of
J. Senior, Esq. A lightning rod, of small dimensions,
of iron, had been set up within 10 feet of the south-
east angle of the building, as used to be the practice
with gunpowder magazines, on the assumption that
the rod would attract the lightning and secure the
building. So far from this, the building itself was
struck in a heavy thunder storm, 28th July, 1857. The
southeast angle was shattered in pieces ; the escape
of the family appears to have been miraculous ;
whilst the lightning rod, 10 feet distant, remained un-
touched. If this building had been a deposit of gun-
powder, it would certainly have blown up.

sir Wm. Snow Harris said : " To detach or insulate
the conductors is to run away from our one princi-
ple, which is, that the conductor is the channel of
communication with the ground, in which the elec-
trical discharge will move in preference to any other
course. To detach or insulate the conductor is to pro-
vide for a contigency at once subversive of our prin-
ciple. Is it possible to conceive that an agency which
can rend rocks and trees, break down perhaps a mile
of dense air, and lay the mast of a ship weighing 18
tons in ruins, is to be arrested in its course by a ring
of glass or pitch, an inch thieh or less, supposing its
course were from any cause determined in that di-
rection ?"

160

VAN NOSTRAND'S ENGINEERING MAGAZINE.

per yard would be quite safe, as shown
in the following table :

Table A.

Iron conductors.

Limits of safety — French
instruction

Side.
[] 0.6"

[]0.75"
[] 0.8"

O1.0"

G"
0.36

0.56
0.64

0.77
0.8

0.6

lbs.
per yd.

3.6

Conductors recommend-
ed by ditto —

from

Sir William Thomson

■"recommended

5.6

6.4

7.7

NewW.O. instructions..
Now proposed for gen-

8.0
6.0

Now iron has about one-seventh, and
good commercial copper about four-fifths
of the conductivity of pure copper.
Hence iron has about one-sixth conduc-
tivity of good commercial copper. A
safe conductor in good copper must
therefore weigh 1 lb. per yard.

It is, however, inconvenient to specify
for a conductor either by sectional area
or by weight per yard, because different
samples of metal, and ^specially of cop-
per, vary considerably in their conduct-
ing power. See Table.

Table of conducting power of differ-
ent descriptions of copper:

Table B.

Pure copper 100

Lake Superior 98.8

Commercial 92.6

Burra Burra 88 . 7

Best selected 81.3

Bright wire 72.2

Tough 71.0

Demidoff 59.3

RioTinto 14.2

Temp, about 15° C. or 60° F.

Imagine a conductor made of Bio
Tinto copper (!) No doubt many exist.

A limit of electrical resistance per
unit of length should therefore figure in
any contract for a lightning conductor,
and for the conductors already recom-
mended this limit would be 0.3 ohm per
1,000 yards, or 0.03 ohms per 100 yards,
at 60°Fahrenheit or 15° C.

This would be obtained from iron wire
rigging ropes weighing 6 lbs. per yard,
or from copper (equal to 80 per cent,
pure in conductivity) ropes weighing 1
lb. per yard.

When two " earths " are used, and the
conductor is carrie'd up one side and
along the ridge and down the other side
of the building to be protected, it is evi-
dent that the conductor may be reduced
in power by one-half, but no further re-
duction can be made when a still greater
number of " earths " are used, because
the lightning may strike the system of
conductors at any point. A 3-lb. iron
(or a half-pound copper) rope is therefore
the smallest that should ever be used in
any situation.

There is much difference of opinion as
to whether iron or copper is the better
material for lightning conductors.

The French use iron almost exclusively,
and Sir W. Thomson prefers it to cop-
per.

For the same money the same conduc-
tivity can be purchased in either metal
(iron being one-sixth of the price and
one- sixth of the conductivity of copper),
and iron has the following advantages :

(a) The mass of an iron conductor

being greater than that of a cop-
per conductor of equal conduc-
tivity, it is heated less by a given
current of electricity.

(b) The fusing point of iron (2,786°

F.) is much higher than that of
copper (1,994° F.).

ductory power than copper of
different samples.

(d) A conductor made of iron is not

so liable to be stolen as copper,
and being so much the stronger
is therefore less liable to be
broken, accidentally or other-
wise.

(e) A copper conductor if connected to

a cast iron water supply pipe (to
form an " earth ") produces gal-
vanic action, to the damage of
the pipe.

On the other hand, a copper conductor
lasts longer in smoky towns or near the
sea shore, where the air rusts iron
quickly, and- being of much smaller size
it does not interfere so much with archi-
tectural effects. But Sir W. Thomson
has suggested that iron conductors
should be treated boldly by architects, and
brought into prominence purposely and
artistically, and the late Professor Clerk
Maxwell recommended that in the case

ON THE PROTECTION OF BUILDINGS FROM LIGHTNING.

161

of new buildings the conductors should

be built into the walls. They would then
not only be hidden but protected from
the weather, from the British workman
carrying out repairs, and from the thief.

As regards the liability of iron to rust,
sjalvaniziiur is in most situations a suf-
ficient protection, and in smoky towns
an iron conductor should be painted
periodically.

On the whole, therefore, the advan-
tages of iron outweigh those of copper
so considerably, that the employment of
copper in lightning conductors should be
the exception instead of the rule.

Those who make, supply, and apply
lightning conductors in this country,
nevertheless, invariably recommed cop-
per ; and it is quite difficult to convince
them to the contrary.

Another point I notice is that large
conductors are always recommended for
lofty buildings, and smaller conductors
for smaller buildings, and the same for
masts of ships. This is unscientific and
wrong. The stroke of lightning falling
on a short conductor is no less powerful
than the stroke that falls on a lofty con-
ductor : indeed the chances are in favor
of the shortest conductors receiving the
heaviest strokes, if they are struck at all.
On costly and important buildings, the
proper course to pursue is to increase
the number of conductors, and of the
earth connections, the limit of electrical
resistance between any possible striking
point and earth being kept below what
is fixed' upon as the point of safety, viz.,
0.3 ohm per 1,000 yards.

We will now examine the question as
to the best form of conductor. Mr.
Preece has investigated this subject, and
by permission of Dr. Warren de la Rue
carried out in that gentleman's splendid
laboratory a series of experiments on the
best sectional form for lightning conduct
ors. The results w^ere communicated
to the British Association at Swansea
last year. He found that ribbons, rods
and tubes, of the same weight per foot,
were equally efficient.

The application of rods and tubes
necessitate frequent joints, generally
made by means of screw collars. I have
found by electrical tests that these joints
after long exposure to weather offer very
high resistances ; especially so in copper
conductors. For instance, at Tipner

magazine a screwed joint in a large tubu-
lar copper conductor tested 1 (),()()() ohms,
and a riveted joint in a ribbon conductor
on a battery in the Isle of Wight 700
ohms. These joints could not be moved
by hand, and were apparently quite
tight.

Fig. 11

Ribbons of copper are now made in
long continuous pieces (as much as 70 or
80 feet in one length), and can be applied
to irregular architectural outlines, but
the joints, although less frequent than

1 with rods and tubes, are open to the

( same objections. The copper ribbon,
however, possesses one decided advan-
tage, viz., that by the introduction of

; suitable bends, the expansion and con-
traction from heat and cold can be al-
lowed for. Iron conductors, when in the
form of tubes, rods, or ribbons, are diffi-
cult to apply, and must possess a number
of joints. Moreover, in long conductors,

j compensators to allow for expansion and
contraction by heat and cold have to be
introduced. In order, therefore, to ob-
tain with iron the necessary continuity
and pliability, it is best to resort to the
wire rope, which form is already very
generally employed for copper conduct-

i ors. Pliability can be obtained in sev-

l eral ways :

1. By using small wTires.

2. By making the rope/A^.

3. By using a hemp core with the
round rope.

It is not advisable to make the iron
wire ropes with very small wires, because
oxidation destroys such a rope rapidly if

162

van nostrand's engineering magazine.

through carelessness the conductor be
left unpainted. A fair amount of plia-
bility can be obtained with a round iron
rope 6 lbs. per yard if the wires are about
No. 11 B.W. gauge, and arranged in six
strands of seven wires each round a hemp
core, thus producing a rope about 3f
inches in circumference.

But there are few situations in which
two ropes of half the size could not be
more readily applied ; and I think the
double rope, if taken up on one side of a
tower and down on the other, in one con-
tinuous length, has many advantages.

When a single conductor is desired,
the best for general purposes is probably
a flat iron wire rope about 2J"x-J-" (11
lbs. per fathom), or 2£"x£" (13 lbs. per
fathom). The round ropes cost from 21s.
to 24s. a cwt., or about 2s. 6d. per fathom
for a 12-lb. rope ; and the flat ropes 33
per cent, more, or add one- third.

The next question that presents itself
is concerning the. terminal point, and a
good deal of nonsense has been written
about it. Points made of silver or of
copper, points covered with platinum or
with gold, points of so many millimeters
in height and diameter, and possessing
certain exact forms, h%ve been proposed,
and rejected or adopted as the case may
be.

The height of the points above the
surrounding roof or tower to be protect-
ed has also been much debated with very
little profit, for to this day many of the
rods erected on the continent are made
much longer than is necessary.

It is a good plan to carry conductors
on lofty rods high above powder mills,
flour mills, and petroleum oil wells ; but
these are exceptional cases, the air close
to the buildings being frequently charged
so as to be dangerously explosive.

The English practice of using a short
rod in most situations is a reasonable
plan, the rod being placed on the highest
part of the building. The rod should
be made of the same metal as the
conductor, and the connection formed
with bolts and afterwards run in with
molten zinc or solder. The weight
of the rod per foot should be the
same as the conductor. The top of each
rod should be provided with several
points, (a) because the gathering power
is increased thereby, and the chance of
lightning striking other things in the im-

mediate vicinity of the conductor is pro-
portionately diminished ; (b) because the
top of the rod is less likely to be fuzed
when struck, the stroke being divided
between the various points ; and finally
(c) because the brush discharge is facili-
tated.*

Another plan is to carry the wire rope
up the side of the rod, which in this case
might have one point, the wires being
opened out to form a brush-like arrange-
ment just under the point. The wire
rope and the rod should be bound to-
gether with wire and connected with
molten zinc.

We must now pass to the foot of the
conductor, and here we enter upon the
most difficult part of our subject. The
earth connections of a lightning conduct-
or constitute the most important portion
of • the whole arrangement. If the elec-
trical resistance of the earth connections
be high, a conductor, perfect in all other
respects, may fail, some alternative and
perhaps dangerous route being taken by
the lightning discharge. It is difficult to
fix the limit of maximum resistance of
the earth connections.

The Academic des Sciences recom-
mends an iron earth plate, consisting of
four arms on a central bar, or five arms
in all, each 2 feet long and of square sec-
tion 0.8 inch side, thus presenting a com-
bined surface of 2.6 square feet, to be im-
mersed in water in a well that never
dries.

Again, Mr. Anderson, in his book be-
fore referred to, says that —

"When a conductor is taken deep enough
into the ground to reach permanent moisture,
the single rope touching it will be quite suffi-
cient. But when the permanency of the moist-
ure is doubtful, it will certainly be advisable
to spread out the rope like the fibers in the root
of a tree."

Here a few square inches touching per-
manent moisture is considered sufficient.
Again, Professsor Melseus used three
earths for the Hotel de Ville at Brussels
— one the gas main, another the water
main, and the third a cast-iron pipe,
nearly 2 feet diameter, sunk in a well
and giving 100 square feet of surface to
the water, which was rendered alkaline

* Sir William Thomson's opinion: " A fork or brush
of three or four points at the top of a lightning rod is
probably in general preferable to a single point; but
of what practical value this preference may be I can-
not tell for certain, although I think it may be consid
erable."

OX HIE PROTECTION OF BUILDINGS FROM LIGHTNING

lft*

with lime to prevent oxidation. The total
surface of these three earth connections
amounts to more than 2] millions of
square feet !

As opinions differ so greatly concern-
ing the surface required for the earth
connections, it will be necessary before
laying down any rule, to give some of
the reasons upon which it is based.

I must ask you to examine Table (C)
of Resistances, which has been compiled
from various authorities, and which deals
with such enormous differences that it
can only be regarded as approximately
accurate.

Table C. — Of Resistances.

Substance.

Pure copper.
Commercial

copper. . .
Iron wire.

Carbon

Coke, variable )

with the sam- >■

pie, about . . . )
Sat. sol. sulph, )

zinc )

Salt (sea) water.
Approximat'y )

only j"

Water (spring).

distilled.

Dry e ar: h )

(practically), f

Comparative Resist-'Effective
ances in Ohms, j Section.

Copper
unity.

1.0

1.17

7.0

2,500

3,000
4,000

6,000,000

10,000,000

15,000,000

2,800,000,000
6,754,000,000

Infinity.

Iron
unity.

0.2

1.0

360

400
600

Sq. in.

0.2

1
Sq. ft.

3
4

10,000

15,000

2,800,000

We might state the figures against
water in this table thus :

The electrical resistance offered by a
cylinder of spring water one yard long is
as great as the resistance offered by a
cylinder of copper of equal diameter,
but seven times longer than the distance
of the moon.

The study of this table involves some
rather curious considerations. Let us
call 1 square inch of iron its efficient sec-
tion* or conductive capability for carry-
ing off a stroke of lightning. Then the
efficient actions of carbon, of water, &c,
are as shown in col. 4 of table.

Now the practice in the War Depart-
ment has always been to give joints in

* This has already heen shown to be rather less than
a square inch of solid iron.

conductors a surface of about six times
the sectional area of the conductor.
This is a very good rule, and is borne
out by the French practice, where even
with Boldered joints, (> square inches of
surface is laid down as necessary at each
joint in an iron conductor. An obvious
corollary to this rule is that when a con-
ductor is made of two metals (end to end)
the joint must have a surface equal to six
times the efficient section of that con-
ductor of the two joined which possesses
the lowest conductivity. The efficient
section of the better conductor ought
not in any way to govern the amount of
surface of the joint. Thus copper to iron
requires a joint of six square inches, the
same as would be required by iron to
iron. In short, the joints should be
made of such a size as to prevent the
conductors of lower conductivity being
damaged by the lightning.

A copper to copper joint only requires
1 square inch of surface, but it is gener-
ally convenient to give more.

Now, the earth connection is really a
joint — a very difficult joint to make well,
and one that should follow the rules of
other joints, unless we can show good
reason to the contrary.

It is found that increasing the size of
an earth plate does not proportionately
decrease the electrical resistance. A
limit of size is soon arrived at, beyond
which it is useless to go. "In the sea
this limit is quickly reached." — (Culley.)

Culley states that if a plate containing
1 square foot of surface give a resistance
of 174 ohms, a plate of 4 square feet
will give 140 ohms, and so on, a reduc-
tion of only 20 per cent, in resistance
being obtained by quadrupling the earth-
plate surface.

The explanation that suggests itself as
probable is that the electric current is
distributed through the humid ground
by an ever-increasing sectional area (often
by an hemispherical surface), thus arriv-
ing at the efficient section for a water
conductor of two millions of square feet
(see Table C), at the small distance of
200 yards, #or thereabouts,* from the
earth plate ; and this is borne out by the
fact, noted by Culley, that the resistance

* In an arid plain with a dry subsoil, the surface of
which was wet by rain only to the depth of one inch,
the efficient section of water conductor would not be
reached at a less distance than fifty miles.

1(54

VAN NOSTRAND'S ENGINEERING MAGAZINE.

depends to a certain extent upon the depth
at which the plate is buried. Thus, a
deep plate would disperse its charge in
all directions by an ever-increasing spheri-
cal surface up to the limit of a sphere
whose radius is equal to the depth of the
plate underground, and afterwards by a
segment of an ever-increasing sphere,
which segment would always in this case
be larger than, but would gradually ap-
proximate, the atmosphere. These ac-
tions are roughly shown on Fig. 12 :

much as the contact between an iron
plate, of whatever form, and coke loosely
surrounding it must frequently be dis-
continuous, and as the conductivity of
coke in a mass composed of loose parti-
cles must be very much lower than that
of a solid piece, the above surface should
in practice be a minimum.

The total surface may, however, be di-
vided if a number of earths be used.

The outer surface which should be
given to the coke must depend very

Fig. 13

JPWiWMMwM

GROUND

DEEP SMALL

SHALLOW

DEEP LARGE

Culley states that the resistance alters
with the depth at which the earth plate
is buried as follows : —

4 inches 100 ohms.

10 " 90 "

40 " , 80 "

80 " ,77 "

It would appear, therefore, that little
is to be gained by increasing the surface
of junction between the earth plate and
the earth (1) beyond the amount required
to insure that the resistance to earth at
foot of conductor is less than the resist-
ance to earth through possible alterna-
tive routes in the vicinity of the conduct-
or, and (2) beyond the amount required
to prevent damage to the conductor by
the flash of lightning when it leaves for
earth. It is evidently impracticable to
give a surface of some millions of square
feet to the earth connections, and if it
were practicable, the foregoing considera-
tions prove, I think, that it is not neces-
sary to do so.

The difference in the conductivity of
iron and water is so enormous that an
intermediary appears to be very desirable,
carbon is eminently suited to act in this
manner, especially if used in the cheap
form of coak and ashes. The minimum
effective section for coke is about 4
square feet, the iron which is surround-
ed by coak should, therefore, have a sur-
face of 24 square feet. Moreover, inas-

much upon the nature of the ground ;
when the conductor is led into soil which
cannot be regarded as permanently damp,
the surface of the carbon " earths " must
be increased.

As the surface of the earth connection
should vary directly as the resistance per
unit of area, an intermediary of coke be-
comes unnecessary where a conductor is
led into salt water; but the conductor
should still present . a total surface to
earth of from 20 to 30 square feet, the
amount being divided between the
" earths " if several conductors be con-
nected.

Professor Pouillet's Committee, which
reported upon the application of conduct-
ors to the Louvre in 1854-55 (the said
report being adopted by the Academie
des Sciences), recommended that when
permanent water is not found near the
surface, two descriptions of " earth " are
necessary; firstly, the deep earth connec-
tions to permanent water, and secondly,
the shallow earth connection to the sur-
face water. This for the following rea-
sons : After a long drought, the " ter-
minating plane of action" (to use Sir
William Snow Harris's term) is situated
on the upper surface of the deep water
bearing strata, the induced charge being
consequently collected there. After a
heavy rain, however, which thoroughly
impregnates the upper strata with water,
the " terminating plane of action " is

o\ THE PROTECTION OF BUILDINGS FROM LIGHTNING.

L65

raised to the surface of the ground, and
the induced charge is accordingly collect-
ed there. It is evident, therefore, that a
perfect arrangement should in many sit-
uations provide both for surface earths
and for deep earths. In some situations,
however, such as the top of a chalk hill,
deep earths would be of little value ;
whereas in other situations surface earths
would be inefficient — in a well-paved
town for instance, where the surface
water is at once earned off by gutters and
drains.

A deep earth connection can be effected
in the manner shown in Fig. 13, the well

Fig. 13

being carried down 10 feet below water
level in the driest seasons. The diame-
ter of the well may be fixed at 3 feet. It
should be rendered alkaline with lime, so
as to protect the iron from rust.

The bottom 10 feet should have no
mortar or cement in the walls, and
should be filled in with blocks of coke.
The iron conductors should terminate in
cast-iron pipes, offering together 24
square feet of outside surface. The pipe
should be galvanized to preserve it from
oxidation. The dimensions of the pipe
may be, length 10 feet, diameter 1 foot.
The pipe may rest on the bottom of the
well, in a vertical position. The best
way to connect the pipe with the conduct-
or is to have a flange at the top (all or-
dinary gas or water pipes have such
flanges), and to rivet a small cylinder to
the inside of the pipe at the upper end,

thus forming a ring or annulus, into
which the end of the conductor can be
introduced, and the space filled in with
molten zinc, the surfaces of the conduct-
or and of the pipe having first been
cleaned and painted with hydrochloric
acid.

In situations where iron water supply
jnpes are at hand, they can be employed
in place of the deep earth connections
already described, but great care must
be devoted to the connections. The con-
ductor must be laid along the iron pipe
for a distance of 4 feet (if an iron wire
rope it should be unlaid for this distance),
it must then be bound to the pipe with
wire, and a metallic connection formed
by means of lead, zinc, or solder. The
connection should then be tarred and
covered with tarred tape to prevent gal-
vanic action.

Surface " earths " should consist of a
trench filled with coke and ashes, and
carried away from the walls. Clay and
other soils which keep the rain-water
near to the surface require shallow
trerches about 1 foot deep ; whereas
gravel, sand, or shingle, through which
the water penetrates easily, require deep-
er trenches, say 2 feet deep.

In each case, however, the top surface
should be kept on the ground level.

The end of the metal conductor should
be carried along the bottom and through
the whole length of each trench. This
length may in ordinary soils be fixed at
25 feet, and in very porous soils at 50
feet.

The water pipes from the roof of the
magazine or building may with advantage
be caused to deliver into gutters which
lead to the surface " earth " trenches.

The shallow trenches, 1 foot deep,
recommended for stiff soils, may con-
veniently be split into a Y shape on plan
(the conductor being split also), so that
the total side surface may be equal to
that given by the same length of deeper
trench used with porous soils.

Important buildings and magazines
provided with several conductors, may
have a few deep " earths," and several
shallow " earths," an " earth " of one or
the other description being provided at
the foot of each vertical conductor, and
in order to connect the whole it is advis-
able to employ a horizontal conductor
near the foot of the wall, but above

166

van nostrand's engineering magazine.

ground in order that it may be open to
inspection, such conductor being care-
fully connected to all the vertical con-
ductors, and to all the metal water pipes.
By this means not only is the cage prin-
ciple advocated by the late Professor
Clerk Maxwell and other physicists em-
bodied, but the earth connections are
connected in an efficient and reliable
manner.

Sir W. Thomson considers that con-
ductors on magazines should be spaced
at intervals of about 50 feet, by which
plan no portion of the building would be
more than 25 feet from a conductor.
This rule has been adopted by the War
Department for all large magazines, and
a conductor of power equal to an iron
rod weighing 8 lbs. per yard has been
adopted for single conductors, and of
half that weight for all others. A wire
rope of 4 lbs. per yard applied as shown
in diagram, is now considered the best
arrangement.

It will be seen that wherever the light-
ning falls a conductivity equal to, or
more than, that of a single large con-
ductor will carry the stroke off to earth.

Small magazines oan be protected by
one rope led to a deep " earth " at one
end and to a shallow " earth " at the
other, as shown on diagram.

Powder mills must be provided with
lofty conductors, to guard as much as
possible against powder dust in the air
being ignited by the stroke.

As regards the inspection of lightning
conductors, opinions vary greatly, and it
was mainly in order to obtain a report
on this matter that I was ordered last
summer to inspect a number of con-
ductors on magazines in the Portsmouth
district. I will read a few extracts from
my report. (See Appendix I.)

Before concluding this paper, I may
observe that the principal object has
been to prove the following points :

1. That iron is the best metal to use in

conductors.

2. That wire ropes are more easily

applied than rods, ribbons, tubes,
&c.

3. That conductors should be con-

tinuous, and that all unavoidable
joints should be soldered.

4. That conductors should be specified

in terms of electrical units.

5. That lofty conductors require no

additional conductivity per unit
of length.

6. That high lightning rods are only

required in exceptional situations.

7. That several points are preferable

to a single point.

8. That greater surface than is usual

with present practice should be
given to earth connections.

9. That both deep and shallow earths

are required.

10. That periodical inspection is most

important.

11. That the history of conductors and

of former tests should be care-
fully recorded.

12. That electrical tests may then be of

value.

APPENDIX I.

I have to report that, in accordance with in-
structions, I have made nearly 500 tests, and
have inspected the whole of the lightning-con-
ductors on fortifications in the Portsmouth and
Gosport Divisions of the southern district, and
have come to the deliberate conclusion, after a
careful study of the subject, that with the light-
ning conductors erected as they are at present by
W.B., electric testing is of small value.

The fact that the conductors on one building
test lower than the conductors on another
building certainly points to the inference that
the earth connections in the former case are of
superior efficiency ; but it does not prove it.
Moreover, although the tests are sometimes of
value to the inspector when he knows the details
of the earth connections from the office records, the
tests taken by themselves are frequently posi-
tively misleading, so far as the earth connec-
tions are concerned. As regards the con-
ductors themselves, above ground, high resist-
ance tests do not prove inefficiency when the
W.O. rule that the surface of the joint shall be
at least six times the sectional area of the con-
ductor is strictly adhered to ; and in this view
I am borne out by Sir William Thomson's
opinion, which now lies before me, viz., "that
although it would be desirable that the joints
should be considered and run in with lead, so
as to make sure of absolute contact, at the
same time it is to be remarked that the great
resistance at imperfect joints is not detrimental
to the lightning conductor, because, when a
discharge takes place, the imperfect joint is
bridged across, and the resistance, which is
very great when tested by a feeble current,
becomes practically annulled in the electric arc
during discharge."

Dr. De la Rue also writes to me and says : -
' ' The resistance of many megohms would
offer an insignificant obstacle to a lightning
discharge, on account of the extremely high
potential of a thunder cloud. Consequently,
a conductor would be quite efficient, although
offering a megohm resistance."

THE PROTECTION <»r BUILDINGS FROM LIGHTNING,

167

The opinion that lightning conductors with
lame surface i>>iiit< rre efficient, although offer-
ing high resistance at ihe joints, la also ^ui>-
aiiated by the well-known action of plate
paratonm rv>. as applied on the flanks of electric
telegraph stationa, to protect the inatrumenis
therein from the effects of strokes of lightning
upon any portion of the line. These paraton-
n&ree consist of plate-, in most patterns smaller
than tlie flat joints of lightning conductors, and
paraffined paper is interposed between the
plat more thoroughly to insulate the

lower plate from '"line. " A number of these
paratonn&res are in >tore at Woolwich, and
tliev each test from 9 to 40 megohms of re^i-t-
ance ; yet in practice a flash of lightning is
always* found to pass across them to good
trth," iu preference to the alternative path
offered through the telegraph instrument,
usually of less" than 2,000 ohms. It is there
fore quite erroneous to suppose that lightning
always pa><es to eartn by those paths which, to
ordinary voltair current, test lowest. It, how-
ever. d< to earth by those paths, which
to a current of its own potential, would test
lowest. . . .

With regard to the conductors now existing
on our magazines and fortifications, and which
have been erected for the most part on sound
principles, and which have never yet failed, it
would appear that the periodical inspection
should be performed by a thoroughly competent
inspector who has studied the subject. He
should be provided with drawings and record
plans, and every information that can be
afforded of each and every conductor in the
district to be inspected. The information con-
cerning the earth connections should be most
minute and exact. He should also be pro-
vided with a light equipment for mating
such electrical tests as he may find necessary.
If this were done, my recent experience would
point to the conclusion that the etectrical tests
would form the least important portions of his
periodical reports. . . .

A- far as my own experience has gone, it
would seem that our conductors are, with few
exceptions, as efficient now as when they were
first put up; but the earth connections of most
of the conductors are and always were con-
siderably below the standard. . . .

Although the lightning conductors at present
on our magazines and forts are no doubt, so far as
the conductors themselves are concerned, effi-
cient, their efficiency could nevertheless be guar-
anteed with greater certainty if more modern
practice were followed. . . .

The adoption of modern practice would at
once make electrical testing of considerable
value, because with unbroken continuity and the
be*t earth connection, all conductors would test
at a very low figure indeed, unless out of order.
An economy would also be effected on all new
works, because metal pipes and rods, with
costly sliding joints to allow for expansion and
contraction, would no longer be required.

A- regards the testing of conductors: a few
tests were taken with the three-coil galvan-
ometer, but with no satisfactory results, as the
instrument is not sufficienly accurate when used
a measurer of electrical resistance. An at-

tempt wa< then made to teal by means .,t the

" earth'" cells produced by the earth of the light
ning conductor, which was always either of cop-
per or iron, and a teal earth of iron or copper.
This gave promise at first of becoming a good

. ihe astatic galvanometer being employed,
hut the method was Boon discarded from want
of accuracy. It is. however, useful for the
tester sometimes tn discdver the metal of the
earth connection of a conductor, and the above
method can then be resorted to. . . .

A quarter-mile of the light insulated wire for
Engineer mountain equipment (00 lbs. per mile)
- cut up into three pieces, each llo yards
long and 4 ohms resistance, and two pieces
each 55 yards long and 2 ohms resistance. This
wire was found to answer well, and being
light, could be carried over a man's shoulder
without any difficulty for considerable dis-
tances

Two small plates (one copper and one iron)
were used, their dimensions being ? inches wide
and 8.^ inches long; they were of oval shape,
and made of quite thin metal. A lip was
formed at the top, and a hole punched in the
plate 2 inches below it; a 2-foot piece of Xavy
demolition cable was then brought through the
lip, passed through the hole, the wires cleared
of insulation for 14 inches, and the ends spread
out like a fan and soldered to the plate. The
lip at the top was then firmly hammered over
the covered wire until it held the wire tightly.
The other end of the piece of core was then
stripped and the wires sweated together ready
for insertion into a brass connector when re-
quired.

A number of resistance tests having been
taken with the P.O. pattern resistance coils, an
astatic, and service six-cell test battery, it was
found that the tests usually ranged below 200
ohms; and I designed an instrument to test
these resistances with approximate accuracy
up to 200 ohms, and to measure roughly up to
2,000 ohms, the bottom plug being placed in
the "xTEX" hole when measuring the higher
resistances. The whole arrangement weighs
less than 6 lbs. when the battery is charged; its
dimensions, moreover, are only 9"xoi' x6 ' over
all, and the method of using it can be tausht
to any intelligent man in a few minutes. The
instrument shown on Fig. 7 is the latest and
improved pattern, and has a range up to 1,110
ohms, when testing direct by steps of 1
ohm ; and to 11.100 ohms by steps of 10
ohms, when using the multiplying hole
marked "xTEX." In testing a conductor's
'earth" the wire to the conductor would be
taken to terminal I/; one pole of the battery
and the wire to the test earth plate to terminal
BL, and the other pole of the battery to termi-
nal B'; the plugs on the upper row of bra-
would then be moved about until no deflection
is produced upon the galvanoscope on the
battery key being pressed down, the bottom
plug being placed in the "EQUAL '* hole. If,
however, the resistance to be found is more
than 1,1)0 (shown b}' above trial) the bottom
plug is moved to the "xTEX" hole, and a
balance obtained and recorded.

The silver chloride battery is used on account
of its small weight, and when kept in a dark

168

VAN NOSTRAND'S ENGINEERED MAGAZINE.

box it is fairly permanent. All the connections
are permanently made, which simplifies the
testing very much indeed. These connections
are all shown in the diagram, and will be un-
derstood by any electrician. The sketch on
Fig. 8 shows the electrical arrangement a little
more graphically. Everything is done perma-
nently, except the connection^ of the unknown
resistance % between terminals L' and BL, the
plugging at R, and the insertion of the EQUAL
or x TEN plug. The tests taken in the Isle
of Wight were performed with the instrument
It saved much time, being very rapid in action
and easily set up. It has also been checked for
accuracy by a series of tests at Woolwich with
satisfactory results.

A special clamp was found to be useful in
connecting the test wire to the conductors, a
small clean spot being produced by a file for
the end of the screw to seat upon. When the
leads had to be connected for long stretches the
naval pattern brass connectors were used.

APPENDIX II.

Extracts from a Memorandum by Colonel H.
Schaw, R.E., 1879, on Lightning Conductors.

" The testing of the electrical resistance of a
system of lightning conductors will general-
ly present great difficulties, because the ordi-
nary means of allowing for expansion and
contraction by slotted joints destroys the
metallic continuity of the conductors, and in-
troduces a variable resistance of oxides and
foreign substances between the slipping sur-
faces.

This resistance will generally be very much
in excess of that of the whole length of the
conductors; it is, however, of little or no
consequence when opposed to electromotive
force of such high tension as a lightning dis-
charge, which will easily pass the obstruc-
tion as exemplified in the form of lightning
protector used by Messrs. Siemens for elec-
tric telegraph stations, which is formed by
two brass plates with roughened surfaces
placed face to face, but prevented from com-
ing into contact by a thin strip of mica.

If the line wire is struck by lightning, the
discharge takes place to earth through the
protector, the two plates becoming opposite-
ly charged by induction, and a spark passing
between them. . . .

The ordinary currents have not a sfficient
tension to pass the air space in the lightning
protector, but go to earth through the more
circuitous route of the instrument.

The test by simple inspection would seem
to be the best for the conductors above
ground. A resistance test could only be ap-
plied with advantage where there were no
slip joints, and where the conductors were
difficult of access.

As regards the earth connection, simple in-
spection may frequently be the easiest and
most satisfactory test also. It is known by
experience that 10 superficial feet of metallic
conductor in contact with icet earth or water
is sufficient to carry off safely any discharge
of lightning. If then we can by inspection

ascertain that in dry summer weather we have
such a connection we may be satisfied.
Should it be difficult to inspect, then the elec-
trical test should be used, and I should pre-
fer the Wheatstone balance test. . . .

It might happen that the connection be-
tween the conductor and the plate, or tube,
or mass of metal forming the earth was im-
perfect, owing to oxidation. In such a case
the resistance would appear considerable,
yet in reality the connections might be prac-
tically good as regards lightning, as a spark
would pass from the conductor to the plate,
&c, and from its large surface of contact with
water it would escape freely and harmlessly. . .

Hence I consider that in all possible cases
inspection is the best test, but that electricity
carefully used may assist the inspection in
cases where the earth connection is difficult to
get at.

It is most necessary that tests or inspections
of earth connections should be made at the dri-
est time of the year. In wet weather they
must always be unreliable.

In rocky or very dry sites good earth con-
nections are most difficult of attainment. ...

I do not think that tests made by weak cur-
rents are of any very great value in deciding
on the resistance of earth connections intended
to carry off a great charge of electricity at one
instant of time, as in the case of a lightning
discharge. H. Schaw, Colonel, R. E.

24th January, 1879.

P. S.— Were all systems of lightning conduct-
ors arranged so that expansion and contraction
might be allowed for by S bands of flat iron
instead of by slip joints, and all other joints
welded or soldered, electrical resistance tests
could be applied without difficulty, and I con-
sider this would be very desirable.

It is a remarkable fact that there was
only one instance of accidental failure in
the automatic drop of the Greenwich
time-ball during the whole of the past
year.

On June 15, the Nature reports that
M . Marcel Deprez delivered, in the large
hall of the Conservatoire des Arts et
Metiers, Paris, a lecture on the trans-
mission of electricity to great distances.
He proved that magneto-electric machines
could be moved through four kilometers
of German silver wire, the resistance of
which was 12 times that of a similar wire
of copper. He also declared that he
could go almost any length in diminish-
ing indefinitely the diameter of the wire
of his dynamo-magnetic machine, and
that it is by resorting to large dynamos
that he will be able to produce a current
sufficiently powerful.

ON THE MAGNETIC u AFTER-EFFECT.

169

ON THE MAGNETIC kt AFTER-EFFECT/ '

By FELIX AUEBBACH.
From •Wiedemann's Annalen.'* for Abstracts of the Institution of Civil Engineers.

In all the magnetic theories of Poisson
and others, the magnetic state of a body
at any time is supposed to depend
merely on the magnetizing forces at this
time.

Under " after-effect " are understood
two kinds of phenomena. The one, the
changing magnetic state of a body during
the action of a constant magnetizing
force, or after the force ceases to act ; the
other being the dependence of magnetic
state not merely on the amount of magne-
tizing force acting at the time, but on the
amounts of these forces which acted be-
fore this time, and the previous conditions
of the body. As to after-effect in elastic
phenomena and in magnetism, the author
mentions the work done by Kohlrausch,
Fromme, Meyer, Warburg, and himself.

The author has already considered, in
a previous communication, " after-effect "
of the second kind. The general ques-
tion which remains to be answered is,
how does the present magnetization, m,
depend on the magnetizing forces J, . .
Jp . . . JQ, respectively, wlncikOave acted
at a previous time when the magnetic

conditions were M,

■ M2,

In the

and this he has tried to answer
present paper, as the question is a com-
plicated one, he gives a qualitative an-
swer, reserving for a future communica-
tion his numerous tables of experimental
results and formulae. The arrangement
of his experiments was the same as in his
first researches. The body operated upon
was a hollow soft iron cylinder, 5£ inches
long, 0.69 inch in diameter, magnetized
by means of a coil of wire. The follow-
ing are some of his results : If. the
magnetizing force t, following on a condi-
tion of no force, would produce the mag-
netization m0 ; then, if besides the force
i acting at present, a series of forces, Jx
. . . Jp . . . J2 . . acted previously, in-
stead of the magnetization m0) there
would now be the very different magnet-
Vol. XXVII.— No. 2—12.

ization m, the difference between them
being the " after-effect " of the previous
forces. J, is of importance in maintain-
ing after-effect, so long as all the succeed-
ing values of J He belween Jl and i, but
after any subsequent value of J lies out-
side these limits, it may be considered
that no after-effect is due to J,. Again,
of two previous forces which He upon
different sides of i, the second alone is of
importance if it Hes farther than the first
from i; in every other case they are both
of importance in determining the value of
m • it is never the case that the first alone
is useful. Permanent magnetization of
steel is a special case of "after-effect,"
and its laws are merely special cases of
general laws. Just as it was found that,
when forces foUowed one another discon-
tinuously, certain intermediate forces are
of consequence, so it is found that, if the
force alters continuously, the rate of
change is without influence on the after-
effect— at least, the influence is smaU in
comparison with the after-effect itself.
If the magnetic force be increased sud-
denly, a magnetization results which de-
creases in time, at first quickly, then
slowly, and approaches a constant value,
which is, however, greater than the con-
stant value produced after very slow pro-
duction of the same force. The rate
change of force is only of influence on the
"after-effect " of the second kind, when it
is so great that it causes an after-effect of
the first kind. Lastly: The magnetic
after-effect is in no case very smaU in
comparison with the magnetic effect it-
self, although it is always less, but be-
tween a value equal to the effect itself
and zero it may have alLvalues. It is not
easy for it to approach the value zero.
The author concludes by saying that no
theory of the cause of the second kind
of after-effect can be worked out till the
phenomena of the first kind of after-effect
are thoroughly mastered.

170

VAN NOSTRAND S ENGINEERING MAGAZINE.

REPORTS OF ENGINEERING SOCIETIES.

American Society of Civil Engineers.
— At a meeting of the Society held on
June 21, a paper by O. Chanute, member Am.
Soc. C. E., subject, " Uniformity of Railway
Rolling Stock," was read and discussed. A
meeting of the Society was held July 5, 1882.
The succeeding meeting will be September 6,
1882.

Engineers' Club op Philadelphia. —
Regular Meeting, June 17th, 1882.

President Rudolph Hering in the chair.

Mr. John T. Boyd described a Shrinking
Gauge, which was designed by Mr. Brown,
general foreman of the works of the Hartford
Engineering Co., and enables the average lathe
hand to make the " shrinking fits," instead of
placing the latter in the hands of one or two
first-class machinists in the establishment,
which is probably the practice in the majority
of machine shops throughout the country.
The gauge resembles, in miniature, an arm
swivel for a tension rod, in which one of the
bolt-ends contains a fine thread screw. The
three screws have each a milled head jamb-nut,
to maintain them in position when adjusted.

To use the gauge, the diameter of the hole in
the wheel-hub, collar, coupling, or lever boss,
as the case may be, is first obtained by bringing
the inside ends of the large screws in contact,
and locking them securely with their respective
jamb-nuts; then running the fine thread screw
out until it calipers or gauges the required dis-
tance; finally locking the last named screw.

One of the large screws is now unlocked and
moved away from the other a distance de-
termined by placing between the inside points
of the large screws, and jambing the same, a
thin strip of metal, which is in reality the
measure of the shrinkage or the difference by
which the diameter of the shaft is to be greater
than the diameter of the hole. The proportion
by which these differences are made is ob-
tained by experiment only and varies with the
sizes and materials.

The gauge is well made of steel, hardened
where necessary, is light and easy to use, and
has a complete set of shrink measures, prop-
erly marked, for different diameters of shafts.

Mr. Geo Burnham, Jr., described a wood
screw in which the thread, instead of being
cut, is formed by passing the blank through a
series of rolling, working against stationary,
dies. The first set forms a slight ridge only,
the second deepens it, and so on until a perfect
thread is formed. The thread of the finished
screw is slightly larger in its outside diameter
than the unthreaded neck of the screw, and the
point is turned conical and left unthreaded,
thus differing from* the ordinary cut screw, in
which the thread continues to the extreme
point. The object of this construction is to
adapt the screw to the present mode of using
it in soft woods; that is, driving it part way
home before using the screwdriver. Bolts are
also made in the same way, the thread appear-
ing to the eye as perfect as a cut thread. It is

claimed that a bolt made in this way is ten per
cent . stronger in the thread than a cut bolt.

Mr. Wm, A. Ingham made some remarks
upon experiments in jigging ore. After pre-
mising that there are two classes of jigging
machines— one in which the tray with the ore
is moved up and down under water, the other
in which the tray is fixed and the water is forced
up and down through the ore bed — he pro-
ceeded to comment upon the difficulty he had
experienced in obtaining from the books fixed
data for the construction of a jig of the second
class. He found that great variations pre-
vailed in the practice at different concentrating
works. The speeds of the water piston ranged
from 48 to 200 per minute and the stroke from
4 in. to i in. There were similar variations in
the sizes of the particles operated on, in the
length of the screen, in the degree of the in-
clination of the bed, and in fact the best prac-
tice varied at every point.

In the face of such diversities, he was
obliged to construct his jig with all its
parts adjustable, and determine for himself
by a series of trials the conditions best adapted
for his work. He soon found that, the
other parts remaining fixed, the results could
be varied as required by merely varying the
piston speed and stroke, and that a high speed
was necessarily connected with a short stroke
and vice versa. He concluded by promising to
prepare a paper on the subject at some future
day.

The following Report was presented:
The Committee of Award of "the Prize
offered by a Member of the Club, May, 1881,"
beg leave to report that they have carefully
considered the papers submitted for compe-
tition, and ha\e awarded the prize of $50.00
for the paper upon a subject strictly in Me-
chanical Engineering, to Mr. Wilfred Lewis, of
Philadelphia, for his paper on the " Applica-
tion of Logarithms to Problems in Gearing;"
and $50.00 for the paper upon a subject of
Civil Engineering, to Mr. P. A. Baermann, of
West Troy, N. Y., for his paper on "What
Thickness of Metal Should be Given to Cast
Iron Pipes Under Pressure;" these being the
two papers winch, in the judgment of your
Committee, conformed the most nearly to the
requirements indicated by the Rules heretofore
published for the guidance of the Committee.
All of which is respectfully submitted.

Fred. Graff, Chairman.

Geo. Burnham. Jr.

Henry G. Morris.
Howard Murphy,

Secretary and Treasurer.

ENGINEERING NOTES.

n^HE Select Ccmmittee of the House of
_L Commons has passed the Bill authorizing
the Solway Junction Railway Company to
raise sufficient capital to reconstruct the via-
duct across the Solway Firth. The new via-
duct will be 1 mile 180 yards in length. The
old one was broken down by a mass of iceflows

ORDNANCE AND NAVAL.

171

in January of last year, as described by u< at
the time. * since then the English and Scotch
lions of this company's railways have been
altogether disconnected. The new bridge will
be constructed under the direction of Mr.
Brunlees, C.E., with wrought iron columns in-
■1 of caal iron.

CM K UK NTs IN Till. SUEZ C an A I.. — By M. de
t Lessens.

A series of very careful observations of the
tides and currents in the seas near the outlets
of the canal, of the tidal waves up the canal.
of the prevailing winds, and of the variations
in level of the seas and lakes, has been taken
from 1872 to the present time. From these ob-
servations it appears that the north and north-
w i -t winds, which prevail from May till Octo-
ber, raise the meiiu level of the sea at Port
Said and lower it at Sue/, producing in Sep-
tember a difference of level of about 1 foot 4
inches, which creates a current, subject, how-
ever, to interruption from the tides, in the
canal from the Mediterranean to the Red Sea.
In the winter the direction of the current is
reversed, owing to the prevalence of southerly
winds and a consequent raising of the mean
level of the Red Sea above that of the Med-
iterranean, amounting in January to 1 foot.
A volume of water is consequently being al-
ternately poured from one sea into the other,
amounting in the year to about 14,000,000,000
cubic feet, which, in conjunction with the
tides, both annihilate the effects of the evap-
oration on the surface of the lakes, and help
to dissolve the salt deposits in ihe Bitter
Lakes. The rate of flow between Port Said
and Timsah Lake varies between 6 inches and
2 feet per second ; and between Suez and the
Bitter Lakes it varies between 2 feet and 4% i
feet per second. These currents do not at
all interfere with the navigation. The dis- !
solving of the salt deposits in the Bitter
Lakes since the}- were filled with water in
1869 has produced an increase in the depth
of water, and affords a refutation to the no-
tion that if the sea were let into the basins in
the African deserts they would soon be con- J
verted, by evaporation, into large salt-beds. — j
Cbmptes rendu* de VAoademde des Sciences.

rj^HE Water Supply of Venice. — Venice,
1 a city of 130,000 inhabitants, with fac-
tories and a naval station, has been notorious
for its defective supply of water of bad quality,
even since the construction of artesian wells in
the last forty years.

In 1868 two proposals were made to the mu-
nicipality, one by Engineer Silvestri, to bring
a supply from the Sile at Canizzano, the other
by a Belgian company to bring water from the
Breuta, in both cases through a conduit along
the railway. In 1875, five more projects were
submitted, one of which, a combined proposal
of civil engineers. Ritterbandt, Dalgarius, and
Ponti, was accepted. Arrangements for carry-
ing out this work were made in 1879 with a
French construction company; the terms of
concession being a rate of nearly Is. 5d. per
100 cubic feet delivered at a height of 164 feet
above ground level, a minimum daily supply

of 1197.180 cubic feet, a storage of 8,580,000

CUbiC feet, and a duration of concession of

sixty years. Finally, some ImprovementH and

general modifications suggested by Engineer

Fumico were adopted with further alteration,

and the works were carried out in general ac-
cordance with them by the Soeieta Veneta.

The supply was taken from the Breuta,
above a dam at 8tra, and conducted by a chan-
nel to the bed of the Seriola, and thence to the
filter beds of Morauzani; the supply is 58 eu.
ft. per second; hut it i- proposed to obtain a
further quantity from a point higher up (he
; stream. The four filter beds have an aggregate
surface of 12,500 sq. ft., the filtering materials
being pebbles, gravel, and sand, and the sur-
rounding walls being carefully constructed to
prevent saline infiltration from the adjoining
salt marshes. The filter beds also act simply
as reservoirs when the Seriola water is so pure
as not to require filtration. Adjoining the fil-
ters is the pumping station, where pumps
driven by a turbine raises the filtered water
into a collecting reservoir. From this the water
is taken in pipes of 2.6 ft. diameter under the
lagoons and salt marshes for a distance of
about "d% miles to Venice. The pipes were
laid by means of coffer-dams, the beds being
pumped dry, and the pipes generally laid in a
concrete trench in the bed of the lagoon. At
passages under deep channels and canals, that
frequently occurred in these lagoons, specially
inverted syphons were employed, and a syphon
crossing over a bridge in the town was also
constructed. The pipes were ordinary cast
iron socket pipes, with lead joints, made by
the Soeieta di Marquise and di Terni, weigh-
ing in all about 2,550 tons. The reservoir at
Venice is built on piles, vaulted and covered
with earth; it holds 3,530,000 cub. ft. of water.
— Engineering Newx.

ORDNANCE AND NAVAL.

rpHE 100-Ton Guns.— The four 100-ton guns
J_ purchased from Sir W. Armstrong &
Co. some time since for £64,000 are still at the
Royal Arsenal — the admiration of all the
strangers who visit that establishment; but to
those initiated in matters of armament, a sad
waste of public money. These unwieldy
monsters are now relegated to Malta and Gib-
raltar, and are already obsolete. It is probable
that they will never fire a shot beyond those at
ordinary practice. Even little of this will take
place, owing to the heavy expense of the
charge, about £100 per round. Taking all cost
into consideration, this sum will barely cover
the value of each discharge from these ugly
and unprofitable weapons. As showing the
way the public money is spent over relatively
useless war material, no less than €24,000 have
been absorbed in the construction of special
shear legs and other appliances for getting
these guns into position in our Mediterranean
fortresses. In addition to this, the War De-
partment steamers have been specially fitted
for carrying the guns out, and will have to
unoretake two voyages in their conveyance.

172

VAN NOSTRAND'S ENGINEERING MAGAZINE.

Then to the cost of this must be added that of
their carriages, which so far has not been made
public, probably £10,000 in addition, so that
these four guns will cost this country over
£100,000. If they were considered by scientific
experts to be trustworthy, even this amount
would not be grudged by the public. But
when it is well known that they were pur-
chased without so much as an adequate trial to
test their capabilities, and that one of the same
construction, and by the same makers, burst
at practice on board the Duillio, the public,
we think, cannot be fairly congratulated upon
the transaction. Matters with respect to the
armament of this country are at present in any-
thing but a satisfactory condition, and the sooner
decisions connected with the national arma-
ment are delegated to a body of able and scien-
tific gentlemen of known reputation, and who
shall be the nation's representatives for this
most important matter, the better it will be
for the British taxpayer, and the safer will the
country be at the time of trial or difficulty.
We certainly think that a Royal Commission
to investigate into the systems of manufacture,
supply, and condition of the national arma-
ment should be granted without the slightest
hesitation. At the present time the national
armament is in the hands of a few, whose only
qualifications are that they are military or
naval men. — Engineering.

HT^HE Armstrong Ribbon Gun. — The firm
J_ of Sir W. Armstrong & Co. has recently
submitted for trial a breech-loading gun upon
a peculiar system of construction. This gun,
though differing but slightly in its breech-load-
ing arrangement from those of the Govern-
ment pattern, is altogether unlike them in gen-
eral appearance and method of building up.
The whole of the piece in rear of the trunnions
is built up of steel wire, over which is shrunk
ordinary yet thinner coils of great tenacity.
The gun's diameter where the charge rests, as
compared with that of the War Office con-
struction, is astonishingly small. Its outlines,
therefore, form those of a long slim weapon.
Yet it is said to be capable of beariDg the ex-
plosion of 300 lbs. of the slow-burning service
powder, with a much heavier weight of shot
than that of the 10.4 in. bore Government gun.
As a matter of fact, however, the exact weight
of shot or shell to be fired with the new gun
has yet to be determined upon by experiment.
So far, the results have been deemed satis-
factory. The weight of the new gun is only
21 tons 4 cwt., yet the diameter of its bore is
10.238 in. Its length is similar to that of the
Royal Gun Factories' 10.4-in. gun of 26 tons.
Should experiments with thisgun prove suc-
cessful, a new departure in construction will
have been taken, and a great step made to-
wards the improvement of our ships and forts.
At a future time we will have more to say con-
cerning this gun and its performances. For
the present, we are inclined to believe that the
construction of the gun does away to a great
extent with the present principle of coil shrink-
ing that creates a bursting strain even while
the gun is quiescent and free from the effects

of the explosive charge. The Royal Gun Fac-
tory is devising and constructing various im-
proved systems of breech-loading arrange-
ments. As experience is gained, a fresh de-
parture in the direction of a better apparatus
is effected, and it is anticipated that the latest
production will altogether throw into the shade
its predecessors. A new obdurator is also be-
ing experimented with on the principle of M.
de Bange, composed of asbestos and mutton
fat compressed by hydraulic power into proper
dimensions and shape, and then fastened in
front of the breech screw. This description
of obdurator appears to answer well so far as
it has been tried. It seems to hermetically seal
up the breech when the explosion of the
charge takes place. The life of this form of
obdurator is estimated to be that of 200 rounds,
at the expiration of which it can be replaced
in the front of the breech screw without much
trouble. If successful, it will supersede the
present form of inverted steel cup loosely fixed
to the breech screw head. — Engineering.

RAILWAY NOTES.

We have received a copy of a pamphlet of
very considerable dimensions contain-
ing "facts from experience " with Cleminson's
flexible wheel base-rolling stock. The facts ex-
tend over six years of working of the system as
applied to carriages and wagons over the
greater part of the world, and of gauges rang-
ing from 23| inches on the North Wales
Narrow-gauge Railway, to 6 feet, as on some
of the Australian lines. We have already fully
described Mr. Cleminson's system as applied
to the royal saloon carriage on the South-
western railway and on many other railways,
in our impression of the 15th February, 1878,
and since referred to its application at home
and abroad. The pamphlet shows that the
system is working with complete success and
economy on 150 railways, consisting of 25
home, 95 foreign, and 30 colonial lines, and on
these lines there are running 26 engines fitted
on the system and over 4,000 carriages and
wagons, while it appears that there are now
over 100 engines building on the system and
2,000 carriages and wagons. The advantages
of the system are chiefly safety and ease in
passing round curves, reduced wear and tear
of rails and flanges, and an increased' carrying
capacity in some cases of 35 per cent., with a
reduction in weight of 25 per cent., as com-
pared with rigid axle rolling-stock. By the
use of three pairs of wheels oa the system,
long carriages may be used, as they are com-
pletely supported from end to end, and follow
curves much more smoothly than the ordinary
short wheel base stock. These advantages are,
it is plain, being fully appreciated, as besides
new stock a good deal of old stock has been
altered to the system.

MECHANICAL POWER ON PARIS TRAMWAYS.
— Those who have had most experience
in the use of steam on the Paris tramways are
perhaps least surprised that after about five
years' trial the system has been abandoned, and

[RON \\l> STEEL NOTES.

173

a return to hone power baa been decided upon.
It is uot too much to say that the design of a
tramway Locomotive for working in the streets
of a city presents more difficult points than the
design of any other class of engine, and hence

the really satisfactory tramway engine has yet

to be made. The objections that are now made
to the engines about to be entirely superseded
by horses are numerous, and some are equally
to be applied to tram-ears hauled in any way;
but the peal objection to these engines has been
the cost of maintenance and working, and the
comparative frequency of stoppage by reason
of breakdowns, of small or great importance.
The Paris company has tried twenty-one differ-
ent engines, and the results are that horse trac-
tion is, on the whole, more satisfactory to the
company. This will probably be felt as a blow
to mechanical propulsion, and no doubt it will
have a retarding effect, but the various causes
of failure and the experience gained will form
the basis upon which engineers must start anew
te make an engine that will stand the abnormal
wear due to bad permanent way, dust, mud,
frequent stoppages and very short curves, and
that can be run without danger by one man.
We have several times given some ideas on the
construction of tramway locomotives, and, un-
til engines are made with parts and fittings that
will be indifferent to dirt and mud, very bad
permanent way and short curves, no success
will be achieved.

In districts where water is largely impreg-
nated with lime, iroD tubes will not answer
for locomotives. Lime is quickly deposited
on the tubes, and it adheres much more strongly
than it would on brass tubes using the same
water; in brass tubes a thin scale of TV to £ in.
thick would be formed, while the incrustation
about the iron tubes would, in a few years,
completely block up the water space between
the tubes: when this takes place, it is impossible
to keep the tubes at the fire-box end tight. To J
prevent the sediment from adhering to the iron,
paraffine oil is recommended, even where brass
tubes are used; about three pints for every
1,000 miles run, put into the boiler the evening
before washing out on the following day, is
mentioned as the quantity. Being free from
acid, this oil is safe to use.

The prospect of a railway through the heart
of Australia, from Fort Darwin to Ade-
laide, is already stimulating enterprise and
speculation. Five hundred miles of this rail-
way, from Adelaide northwards, the Colo nits
and India says, have already been completed;
100 miles from Port Darwin, in a southerly
direction, are likely to be soon authorized by
the Government; and the construction of the
remainder is but a question of time. Another
railway, in Queensland, connecting Brisbane I
with the Gulf of Carpenteria, and possibly ulti-
mately meeting the line from lort Darwin, is,
also projected, and must have a remarkable i
effect in developing the resources of the north- ,
eru half of the Australian continent. With
these railways built, those fertile parts of the
continent, which have hitherto received but
scant notice from the capitalist and the laborer

alike, will take rank among the .richest portions
of the British Empire.

IRON AND STEEL NOTES.

Ri ii' r for Bhon/.im; Ikon.— Iron ha>
sometimes to be bronzed for domestic
QSe, The following is a very simple way of
obtaining a very good bronze: Mix an equal
quantity of butter of antimony and oil of oh \
put this mixture on the iron which is required
to be bronzed with a brush, the iron having
been previously brightened with emery and
cloth, and leave it for several hours; then rub
with wax and varnish with copal.

Melting Steel by Electricity. — An in-
teresting experiment made by Mr. Sie-
mens a short time ago, in tne presence of a
large number of practical electricians, is de-
scribed in a French journal. A number of
broken pieces of steel were put in a suitably
arranged crucible, with a perforated lid to it,
the two currents of the electro-motor terminat-
ing in the upper and lower part of the crucible.
In fourteen minutes the entire mass of metal
was heated, turned red, and liquefied. There
was not a single bubble in the mass. The cost
of fuel required for this apparatus is very much
less than that which would be wanted if the
fusion were effected by the direct application
of the heat. A considerable saving may conse-
quently be effected in steel works if this process
is generally adopted.

The Staffordshire Steel-Making Ex-
periments.— Mr. P. C. Gilchrist, and
the Committee of Staffordshire ironmasters
with whom he is associated in the conducting
of experiments at Wednesbury, which aim at
the making of basic Bessemer steel from Staf-
fordshire cinder pigs, have brought their labors
to a close. One hundred tons of pigs probably
have been blown, and perhaps seventy tons of
ingots made. Middlesbrough pigs are com-
puted to contain about 1| per cent, of phos-
phorus. The phosphorus in the Staffordshire
pigs, which have been most largely used, is
about 3 per cent. With such pigs the results
were obtained which were last week described
iu The Engineer. Since that time pigs in which
the quantity of phosphorus is estimated at as
high as 4-J per cent, have been blown. These,
treated by Mr. Gilchrist with an extra propor-
tion of lime, have made slabs and billets deemed
by that inventor to be in no way inferior to
those resulting from the u-e of pigs with 3 per
cent, of phosphorus. Arrangements have been
made for completely testing all the slabs and
billets. Eighteen firms are now receiving lots
of from two or three to five tons apiece.
Treated in the ordinary iron mill, these slabs
will be rolled out as if they were piles made of
puJdled iron or scrap, and the sheet or strip, or
what-not, will be experimented with by the
stampers, the tin-plate makers, the tube makers,
and the rest. Upon the reports of the testing
firms will largely depend the adoption of the
basic Bessemer process iu districts where com-
mon pigs are abundant but high qualities of
hematite pigs scarce. — Engineer.

174

VAN NOSTUAND.s KN(iIN KVAll N(i MAGAZINE.

MANUFACTURE OF STEEL AND INGOT IRON
from Phosphortc Pig Iron. — At the
Society Of Ails, in April last, a paper was read
by Sidney Gilchrist 'I homas and Percy C. Gil-
christ on the manufacture of steel and ingot
iron from phosphoric pig iron. The authors,
after stating thai nearly nine-tenths of the iron
ores of Europe were so phosphoric as to pro-
duce a pig iron unfit for steel-unking "without
a process of dephosphorization, showed that by
the new lime process peilYct dephosphorization
was produced so that the steel made from
phosphoric pig was actually purer than that
made from hematite iron. They then instituted
a comparison between the basic Bessemer pro-
cess and the puddling process, pointing out
that the former process was peculiarly adapted
to (he manufacture of soft weld able steel, hav-
ing all the characteristics of puddled iron with
considerably greater Strength, elasticity, and
dnctility. It was stated that this soft basic
Bessemer steel could be made for some shil-
lings a ton less than ordinary puddled iron,
while an economy of 7s. a ton was gained in
its subsequent treatment by the smaller loss
which it undergoes in rolling. The authors
stated that nearly half a million tons a year of
the new dephosphorized metal were now being
made, and that on the Continent works were
erecting, having a capacity of a further half
million tons a year, while in England the new
special works erecting had only a capacity of
under 200,000 tons a year. The paper con-
cluded by querrying the wisdom of allowing
Continental ironmasters to pusfi so far ahead of
us in the production of this new ingot iron,
which was not only cheaper but immensely su-
perior to puddled iron. — London Paper.

SELF Winding Clock.— In September last,
a new perpetual clock was put- up at the
Gare du Notd, Brussels, in such a position as
to be fully exposed to the influence of wind
and weather ; and although it has not since
been touched, it has continued to keep good
time ever since. The weight is kept constantly
wound up by a fan, placed in a chimney. As
soon as it approaches the extreme height of its
course, it actuates a brake, which stops the
fan; and the greater the tendency of the fan
to revolve, so much the more strongly does the
brake act to prevent it. A simple pawl arrange
ment prevents a down draught, from exerting
any effect, There is no necessity for a tin;, as
the natural draught of a chimney or pipe is sufli-
cient ; and if the clock is placed out of doors,
all that is required is to place above it a pipe,
16 or 20 feet high. The (dock is usually made
to work for 24 hours niter being wound up, so
as to provide for any temporary stoppage; ; but
by tin; addition of a wheel or two, it, may be
made to go for eight days alter cessation of
winding. The inventor, M. Auguste Dardenne,
a native of Belgium, showed his original model
at the Paris Exhibition of 1878 ; but has since
considerably improved upon it,

Pure Carbons FOR the Electric Light.—
At the meeting of the Paris Academy of
Science on 27th March, M. .laequelain pointed
out that carbon for the electric light should be

purer than that obtained by calcining wood ;
and, if not free from hydrogen, should, at any
rate, contain no mineral impurities. There are
three methods for accomplishing this result :
(1) By the action of a jet of dry chlorine gas
directed on the carbon, raised to a light red
heat ; (2) by the action of potash and caustic

poda in fusion ; and (8) by the action of hydro-
fluoric acid on the finished carbons. M.
laequelain has prepared carbons by all three
methods, and has summed up, in a table, the

photometric results of his experiments, lie

comes to the conclusion that the luminous
power and the regularity of the voltaic arc in
crease in direct ratio to the density, hardness,
and purity of the carbons. He remarked, inci-
dentally, that the natural graph it oYd of Siberia
possesses the singular and unexpected property

of acquiring, by purification, a luminous capac-
ity double that winch it has in the natural state.
and which exceeds by one-sixth that, of pun;
artificial carbons.

BOOK NOTICES

PUBLICATIONS RECEIVED.
PROCEEDINGS OF THE A.MERI0AN SociETY

of Mechanical Engineers.

OUKNAL OF THE ASSOCIATION OK K.NU1-

neerino Societies.

ABSTRACTS OF FOREIGN TRANSACTIONS,
PREPARED FOR INSTITUTION OK Civil.

Engineers.

ousehold Chemistry for the Non-
chemical. By A. J. Shelton, P.C 8.
London: F. V. White & Co.

This is a work which strongly reminds us of
the late Prof. Johnston's ' • Chemistry ol Com-
mon Life." The writer, indeed, admits in his
preface that many books have been written on
the chemistry of things commonly met with in
daily life, but contends that they have bgen at
fault "in at least one particular," i.e., in con-
taining a quantity of matter "not of a strictly
chemical nature, and which, however interest-
ing in itself, swells the book to a large size
without adding to its usefulness." It might
perhaps hen; be remarked that matter not
strictly chemical may yet be very useful, and
may be Legitimately introduced into works of

a popular class. Indeed, in describing, as the
author proposes to do, "certain chemical prin-
ciples and processes involved in some house-
hold operations," it will not always be found
easy to eliminate physical and physiological
considerations.

Mr. Shilton devotes his first, chapter to
"chemical preliminaries." In the second he
treats of washing soda, common salt, and other
sodium compounds, and describes briefly the

alkali manufacture. The manufactures of soap

and of candles are next sketched. As regards
the latter subject it may be asked whether, as
the processes of candle-making are mainly me-
chanical, the author is not, like his predeces-
sors, introducing matter which is "not of a
strictly chemical nature."

Ozone, though if figures as an item on the

BOOK NOTICES.

175

cover of the book, is but slightly QOticed In
the text. We are glad to find thai the author
shows himself sceptical as to the alleged wou-
derful powers ascribed to this compound. Be
veu hard-hearted enough to inform the
British public that, the peculiar odor which
they greedily inhale at the seaside and regard
a9 a panacea consists principally of the efflu-
vium of "decomposing crabs and seaweed."
As regards the proportion of carbonic acid in
the air, the chief weight is still laid, as in
older manuals, upon its production by the respi-
ration of animals and by combustion, and ou
its decomposition in the nutrition of plants.
But we find no mention of a pair of processes
which are at work on a probably larger scale,

. on the one hand the exhalation of carbonic
acid from volcanoes, and on the other, its
withdrawal from the atmosphere in the form
of calcium carbonate by certain processes of
marine animal life, especially by the coral
worms.

The chapter on water contains some very
sound advice, and we are glad to perceive that
the author gives his vote for soft wate'r as the
more suitable for domestic purposes. The cost
of softening a hard water by dint of soap is
£47 Is. 8d., as against 8d. for doing the same
work by Clark's process. A section on disin-
fectants, though correct in its statements, does
little more than show how very limited as yet I
is man's power of dealing with disease germs.

Succeeding chapters deal with starch, the
sugars, the manufacture of bread, though with- j
out any reference to the ultra-filthiness of our
modern town bakeries, fermentation, distilling,
wines, where the "plastering" fraud is duly
denounced, vinegar, the infused beverages, the
glass and porcelain manufactures, and the
chemistry of food. As the entire compass of
the book falls short of 200 pages, not very
closely printed, it need scarcely be said that
these subjects can be but briefly dealt with. The
author, however, may fairly be said to have
made the best of his narrow space, and to have
given a clear summary of his subjects.

DYEING AND TISSUE PRINTING. By W.
Crookes, F R. S. (Technological Hand-
books.) Edited by H. TruemanWood, Sec-
retary of ihe Society of Arts.) London : G.
Bell and Sons.

Those of our readears who have taken an
interest in the City and Guilds of London In-
stitute for the Advancement of Technical Edu-
cation will be aware that the want of a series
of manuals specially adapted for the use of
students preparing for the examinations of the
Institute soon made itself felt. On the tincto-
rial arts, for instance, there certainly existed
important and valuable treatises. But they
were for the most part too costly for students,
many of whom would probably be of limited
means. Other works, again, were unsuitable
because they did not begin at the alphabet of
arts in question. What was needed, therefore,
was a handbook, not too costly, plain, and
simple in its style, covering the whole ground,
and making no special demands upon the
previous knowledge of the student. Mr.
Crookes has undertaken the somewhat difficult

task of drawing up such a work, and appears
to have succeeded in fulfilling the various con-
ditions above laid down. The only previous
qualification Of which the student is assumed to
be possessed is an elementary knowledge; of
Chemistry, such as may be acquired from
almost any of the rudimentary treatises on that
science. The author, building upon this founda-
tion, seeks to explain the principles of the art
from a practical rather than from a theoretical
point of view. From the very outset he
endeavors to explain everything with
which the learner might be puzzled. In the
preface there are given explanations of certain
measures used in dye-works, &c, and little
known elsewhere. In the " General Introduc-
tion " the first point brought forward is the
cleansing of the goods to be operated upon — a
matter in which even experienced dyers are
often sadly indifferent, and thus insure an un-
suspected source of blunders, which are
charged against the dye-wares or the mordants,
and which can often be rectified only by the
expenditure of much time and trouble. Mr.
Crookes even demands, as far as is humanly
possible, chemical purity in the vessels used,
in the materials to be dyed, in the water, and
in the dye-wares. We know that good results
are often produced without the observance of
these conditions, but we know also that a
prudent man will, if possible, avoid the risk.
Half the skill employed in "cobbling" pieces
which have come up spotty, or flat, or smeary,
would have prevented these evils, and given a
far better result.

At this part of the treatise a description is
given of the procedures for bleaching the
different textile fibers, that is, freeing them
from their natural coloring-matters, which in
many cases if let remain would be as fatal as
artificial dirt.

The next section, on the selection of water
I for dye and print-works, has been evidently
written with great care. The author points
out what kinds of water are needed, from what
geological formations it may best be obtained,
! and what possible ingredients are to be especially
j avoided. It may here be remarked that the
I water needed for tinctorial purposes, and,
indeed, for the industrial arts generally, is not
the same quality as that which sanitary reform-
ers demand for domestic purposes. For dietetic
purposes the presence of salts of lime, and
even of magnesia and iron, to a moderate
extent, is not objected to. For the dyer or the
printer, iron is fatal, and compounds of
calcium and magnesium greatly interfere writh
many of his operations. Processes are given
for the detection of the ordinary impurities,
and for their removal, when necessary, upon
the large scale.

Next follows a chapter on mordants. Here
the author enters a little more into theoretical
considerations than iu most parts of the work.
He shows that if the action of the metallic
mordants and the nature of the aniline colors
had been better understood, practical men
might have been saved the trouble of tedious
attempts to fasten, e. g., magenta upon cotton
fiber by means of alumiuiun acetate or sulphate.
Surely, even those who talk most loudly of the

176

VAN NOSTRAND'S ENGINEERING MAGAZINE.

uselessness of what they are pleased to brand
as mere "book-knowledge," might see the
necessity of having some acquaintance with
the properties of the agents they use. To
argue that because magenta is a red color it
must be capable of fixation in the same manner
as cochineal, is not, after all, a very practical
procedure. The instructions for the prepara-
tion of nitrate of iron rank among the fullest
which have ever been printed, and speak of
close and extensive observation.

The accounts of the astringents, of the fatty
and the animal mordants— commonly so-called —
are exceedingly thorough going.

In the "General Instructions on Dyeing"
we find not a little matter which it is probable
has never appeared in print before, having prob-
ably been overlooked as too elementary. AmOng
other needful matter we find here the introduc-
tion of certain technical terms, which would
greatly perplex the tyro on his introduction to
practical work. Here, also, are plain direc-
tions for "matching off" colors, i.e., for com-
paring the goods dyed with the pattern sent as
a standard.

After these general and introductory con-
siderations, follow a series of receipts for
obtaining different colors upon cotton. It
has evidently been the author's object to
exemplify the methods required for dealing
with cotton in its different states, such as cotton-
wool, yarns, piece-goods of various kinds,
such as calico, cotton-velvets, cords, &c. , and
to show the processes for applying the new
colors.

After cotton, linen, jute, wool, and silk, are
worked through in a similar style, the charac-
teristic features of each staple being noticed in
a few preliminary remarks.

The latter half of the book is devoted to
tissue-printing in its various styles and branches.
It cannot be denied that the work would have
been more useful had it been illustrated with
dyed and printed patterns, diagrams of machin-
ery, &c. But such additions would have
involved such an increase in the price of the
book as to be out of the question. For the
purpose in view this treastise will form a sound
and useful basis for the student. — Chemical
Review.

MISCELLANEOUS.

In the Belgian Academy, M. Plateau has
lately called attention to a small illusion.
He describes an arrangement, which, at first
sight, he says, might be thought capable of real-
izing perpetual motion. A capillary tube is in-
serted obliquely in distilled water, so that the
latter nearly fills it. Into this liquid column,
at the top, dips the small orifice of another
tube, which reaches a little way in the same
oblique direction, then turns downwards, the
vertical portion being wider, and not reaching
the water. Suppose this bent tube filled with
water. It then forms a siphon, the shorter
branch of which is immersed in a liquid in
equilibrium, while the longer descends several
centimeters below the surface of that liquid.

Does it not appear as though the water should
flow# incesantly through the siphon, and, re-
gaining the vessel, be engaged in perpetual cir-
culation ? As a matter of fact, the water is
drawn upwards in the vertical portion of tube
till its free surface reaches a part of the oblique
part of the same tube, when it stops. M. Pla-
teau accounts for the effects by suction exerted
by the small concave liquid surface between
the two tubes.

The fourth number of the Memoirs of the
Science Department of the University of
Tokio is a monograph on the geology of the
environs of Tokio, by Prof. Brauns; while the
fifth contains a paper by Prof. Mendenhall on
the force of gravity at Tokio and on the sum-
mit of Fujiyama. Dr. Naumann, the head of
the Japanese Geological Survey, has recently
published a monograph on Japanese elephants.
The writer has found remains of these mam-
mals in various widely separated districts.
This paper will be found in vol. xxviii. of the
" Palaeontographica," published by Fischer of
Cassel, and is entitled " Ueber Japanische Ele-
phanten der Vorzeit."

An alleged invention of a German chemist,
by which cotton and woolen fabrics
could be coated with a layer of dissolved silk
and made to assume the glossy and soft ap-
pearance of actual silk goods, was recently de-
scribed by the Colonies and India. Experi-
ments in a somewhat similar direction appear
to have been made by a French chemist, who,
however, coats his material with a thin layer
of tin instead of silk. He first makes a mix-
ture of zinc powder and dissolved albumen,
which he spreads over the fabric by means of a
brush, leaving it to dry, when the stuff is
passed first through superheated steam, and
afterwards through a solution of chloride of
tin. By this means an exceedingly thin layer
of tin is spread over the whole side of the
fabric, which is thus rendered waterproof, and
protected against erdinary rough usage. The
utility of the invention probably consists in the
preparation of theatrical dresses, and even in
the bright "trimmings" the invention might
find a limited application.

Stannous hydrate may lose its water and
become transformed into crystals of the
anhydrous oxide under circumstances which
are complex and imperfectly known. The
crystallization may occur either in acid or alka-
line liquids. The acids with reference to oxide
of tin may he divided into two groups. Those
of the one group give, with this oxide, salts
which are entirely decomposed by boiling
water, and determine its transformation into
the crystalline oxide in consequence of success-
ive reactions. These salts, decomposable by
water, yield, free acid, and behave absolutely
like the acids themselves, determining the crys-
tallization of stannous oxide. The acids of the
second class do not give rise to these successive
reactions, and the hydrated stannous oxide
never becomes anhydrous and crystalline under
their influence.

VAN NOSTRAND'S

Engineering Magazine.

NO. CLXV.-SEPTEMBER, 1882 -VOL. XXVII.

ON THE NECESSITY OF GOVERNMENT AID IN ORGANIZING

A SYSTEM OF TESTS OF MATERIALS USED

FOR STRUCTURAL PURPOSES.

By CHARLES MACDONALD.
A Paper read at the Washington Meeting of American Institute of Mining Engineers.

It may seem to be almost unnecessary
to occupy the time of the Institute in
further consideration of a question which
has been so comprehensively treated in
papers already on file in our own Trans-
actions and in those of the American So-
ciety of Civil Engineers.

Unfortunatelv, however, the results of
these concerted efforts have not been to
materially increase our stock of knowl-
edge in the direction sought for ; and as
the necessity for this information is be-
coming more and more apparent as the
demand for structural materials in-
creases, it is believed that by continuing
the agitation by means of discussions in
this and kindred societies, whose mem-
bers are vitally interested in obtaining
reliable data as to the properties of the
materials they are called upon to work
with, public opinion ma}- be educated up
to the importance of exerting such an
influence upon the law makers of the
country as will result in the formation
of a competent board, with adequate
means at its disposal, to carry out this
great work in a manner alike accept-
able to the makers and users of the
materials in question.

It may be proper in the first place to
Vol. XXVII.— No. 3—13.

glance briefly at what has been at-
tempted thus far, then to indicate some
of the more important lines of needed
investigation, and finally to consider rea-
sons why Government aid may with
propriety be sought for in carrying on
the work.

At a Convention of the Society of
Civil Engineers, held at Chicago, June
5th, 1872, it was, on motion of General
William Sooy Smith, resolved, that

Whereas, American engineers are
now mainly dependent upon formulae
for the calculation of strength of the
different forms of iron and steel, not
based on experiments upon American
materials and manufacture ; and

Whereas, These differ greatly in many
of their characteristics from those of for-
eign production, both in their nature and
forms; therefore,

Resolved, That a committee of five be
appointed to urge upon the United
States Government the importance of a
thorough and complete series of tests of
American iron and steel, and the great
value of formulae to be deduced from
such experiments.

Pursuant to this resolution a commit-
tee was appointed, by whose efforts Con-

178

VAN NOSTRAND'S ENGINEERING MAGAZINE.

gress was induced to pass a law, March
4th, 1875, providing for the appointment
of a United States Board to Test Iron
and Steel, and an appropriation of seven-
ty-five thousand dollars ($75,000) was
made for that purpose.

The board appointed under the law
above referred to consisted of Colonel
T. T. S. Laidley, Ordnance Department,
U. S. A.; Commander L. A. Beardslee,
U. S. N.; Lieutenant-Colonel Q. A. Gill-
more, U. S. A.; Chief Engineer David
Smith, U. S. N.; William Sooy Smith,
C.E.; A. L. Holley, C.E.; K. H. Thurs-
ton, A.M., C.E., Secretary; and they
were ordered to report from time to time
to the President of the United States.

The first and most important duty of
the board was deemed to provide an ac-
curate testing machine. This proved to
be a more serious matter than was at
first supposed. There were no machines
in the country which could be considered
as giving anything more than approxi-
mate results ; and to construct a new
machine upon approved principles re-
quired much time and a large expendi-
ture of money ; much more, in fact, than
was represented by the mim paid for it.
At length a machine was completed,
which for accuracy of the results ob-
tained and range of power exerted, is
unequaled, perhaps, in the world. Ow-
ing to the length of time expended in
completing it, however, the original ap-
propriation became exhausted, and the
board was legislated out of existence,
having had scarcely an opportunity to
verify the capabilities of the very instru-
ment which had been brought to perfec-
tion under its fostering care, and
through the proper use of which so
much valuable information could be ob-
tained.

As might have been supposed, the
board did not confine its efforts to the
construction of this machine. About 150
specimens of steel were analyzed, and
tests of their physical and mechanical
properties made with a view to deter-
mine the relations between chemical con-
stitution and useful qualities.

In wrought iron the effects of reheat-
ing and rerolling were carefully exam-
ined, and the report contains valuable
information as to the different processes
of making and rolling iron, the effects of
various kinds of strain, the best methods

of making cables for large vessels, and
to determine how uniform strength can
be secured in iron of different sizes in
the bar, and how to make large masses
equally strong with small pieces.

Alloys of copper-zinc and copper-tin-
zinc were exhaustively examined and the
results exhibited on a small triangular
model from which may be obtained by
inspection the characteristics of any pos-
sible combination of these metals.

Extensive preparations had also been
made for ascertaining experimentally the
strength of rolled beams and shape
irons, for which we are now dependent
almost entirely upon theoretical form-
ulas.

Although the board had ceased to ex-
ist, the machine remained the property
of the United States. It is located in
the Watertown Arsenal, near Boston,
under the immediate charge of the Ord-
nance Department of the army, and is
nominally at the service of engineers and
others who may be able to defray the
necessarily heavy expense of working it
for their own private benefit. So much
for what has already been accomplished.
Should the efforts now being made to
revive interest in the subject prove suc-
cessful, the field for investigation will be
found to be most fruitful of results. To
mention a few instances only : In the
department of bridges there were re-
quired for last year's construction not
less than 80,000 tons of Iron and steel
representing, say, 50 miles of bridges,
over which the safety of life and limb is
supposed to be assured by the accuracy
of the calculations of the designer, no
less than the quality of the material em-
ployed. Of this material upwards of 35
per cent, is in the form of compound sec-
tions specially adapted to resist com-
pressive strains ; and yet until quite re-
cently all the experimental data upon
which such sections are designed were
obtained through the instrumentality of
testing-machines which, particularly at
high pressure, are liable to give very er-
roneous results.

Quoting from Mr. Holley's paper on
the United States Testing-machine at
Watertown, alluding to C. E. Emery's
device for overcoming packing friction :

" It is certainly worth many times its
cost in proving the worthlessnes of hy-
draulic testing-machines as heretofore

TESTS OF MATERIALS FOR STRUCTURAL PURPOSES.

179

constructed. The readings of the per-
manent weighing apparatus as compared
with those of the cylinder gauge when
the piston was not revolving, showed in
some cases an error of 40 per cent."

It is safe to say that the recent fall of
one of the most important bridges in the
country would not have occurred, if, at
the time of its construction, the engi-
neer could have tested full-sized sections
of his material on such a machine as the
Government now owns at Watertown
Arsenal.

The tension members of bridges are
in the form of eyebars varying in sec-
tional area from one inch to twenty
inches. Until quite recently it was as-
sumed that the same strain per square
inch might be applied indiscriminately
without regard to the size of the mem-
bers, or to the amount of work done
upon the material in the rolls ; but the
few bars which have already been tested
at Watertown clearly indicate that this is
a most erroneous assumption ; and one
of the first duties of a testing board
would be to establish the law governing
the diminution of strength due to in-
creased section, and to establish the re-
lation between ductility and ultimate
strength. Then would follow tests to
determine proper form of head, and such
other details of manufacture as might
suggest themselves.

Of rolled beams there were produced
last year upwards of 50,000 tons. This
form of product is used chiefly in floors
of buildings, often to sustain great
weight, as in warehouses, and somewhat
also as stringers in bridges. Their
strength is estimated by theoretical form-
ulas in which the physical constants
are taken from experiments upon foreign
irons tested under circumstances en-
tirely different from what are obtained
in actual practice. Fortunately for the
cuase of safety in the use of such ma-
terials it is probable that the formulas in
question do not represent the full
strength, and that a considerable amount
of unnecessary weight is loaded upon
our structures in consequence ; but there
is all the more reason why the actual
strength should be determined by ex-
periment, in order that an uniform
factor of safety may apply to every mem-
ber of a structure, or in other words, that
it shall be equally strong in all its parts.

Did time permit, it would be possible
to point out many other directions in
which experimental knowledge is sadly
needed, but if nothing else were done
than to determine practically the laws
which govern the strength of compres-
sion and tension members of bridges,
and the flexure of rolled beams, a very
great advance would be made in our
modes of construction, and a greater
safety would be assured to the hundreds
of thousands of people who are constant-
ly trusting their lives upon such struct-
ures.

What has been said regarding the im-
portance of testing particular construc-
tions applies equally to iron and to
steel ; but there are special reasons for
investigating the properities of steel
which should command attention. It is
admitted to be the metal of the future,
for large constructions at least; it is
stronger and more homogeneous than the
best iron, and owing to the substitution
of mechanical appliances for wasteful
muscular effort in its manufacture, there
will come a time, and that before very long,
when it can be furnished commercially at
less cost than iron, in large quantities
and of uniform quality. It only remains
now to determine by a competent and
disinterested authority what the general
characteristics of this material are, to in-
sure for it a continually increasing de-
mand.

At present the finished product of the
converter is principally in the form of
steel rails. It so happens that the best
testing-machine for a steel rail is the
track, and railroad companies, by careful
inspection, taken in connection with chem-
i ical analysis, are thus experimentally de-
| termining the quality of steel which an-
swers best for that particular purpose.

For other constructions, such as
bridge and ship work, very different
qualities of steel are required, depend-
ing on the nature and direction of the
forces to which it is subjected; and un-
til all such questions are determined by
competent and disinterested investigat-
ors, the benefits to be derived from the
cheap production of steel by the pneu-
matic or open-hearth processes, will for
a long time be confined to the favored
j few who are engaged in supplying the
demand for steel rails.

It is hoped that eaough has been said

180

VAN NOSTRAND'S ENGINEERING MAGAZINE.

to establish the fact that a producing
class of the community stands in want
to-day of certain scientific information,
which, if obtained promptly and in a
manner to command universal accept-
ance, would tend to improve and enlarge
one of the staple industries of the coun-
try. From the nature of the case such
information can best be obtained by the
assistance of the general government.
Shall the effort be made to secure such
assistance?

It may be asked, why should the
United States Government appropriate
money for the purpose of making ex-
perimental investigations which might as
well be undertaken by those who are
immediately interested? In reply to
to this, the following quotation from the
memorial recently presented to Congress
by the American Society of Civil Engi-
neers will commend itself:

" And your memorialists further rep-
resent that there is no prospect that the
necessary tests will be made without the
aid of government. Should private
manufacturers or builders test their own
materials they might not give the public
the benefit of their experiments ; such
experiments would not have that assur-
ance or impartiality and that high au-
thority which those made under the au-
thority of the government would have.
Experiments conducted by private par-
ties would be so different in the objects,
methods, and circumstances of applying
tests as to render it impossible to prop-
erly collate and verify them ; they would
therefore be of comparatively little value
in ascertaining accurate general re-
sults."

I am aware that it is often a difficult
matter for legislators to draw the line
between public and private interests,
and that in the multiplicity of claims
made upon them they must be expected
to look doubtingly upon anything that
calls for money ; but it would seem that
where such enormous revenues are de-
rived by the country from the effort to
secure the exclusive consumption of
American manufactures of iron and
steel, it would be asking no more than
justice for the users of these materials
that the government should lend sub-
stantial aid in determining their general
characteristics.

Again, the government of the United

States is in possession of a most impor-
tant element in the problem, the testing-
machine already referred to ; it repre-
sents a very considerable expenditure in
money and years of patient labor, which,
it is safe to say, would never have been
expended had there not been a well-
grounded hope that an amount of knowl-
edge would be obtained through its instru-
mentality which would contribute largely
to the general good.

In its present shape this machine is
utterly unable to meet the wants of even
such private demands as are made upon
it. I am informed by an engineer now
engaged in the construction of one of
the most important bridges in the coun-
try, that he recently sent to Watertown
nine steel eyebars to be tested, and it
required seven and a half days to make
the tests, while the cost to his company
was at the rate of $15 for each bar. This
is admitted to be due to the fact that
there are no means at the disposal of the
department wherewith to engage an effi-
cient permanent staff of assistants to
handle the specimens promptly, and the
result is that a most valuable instrument
for scientific research is allowed to re-
main in comparative idleness for the
want of a few thousand dollars.

As to the most effectual means of ex-
pending government aid in the direc-
tion sought, there may be difference of
opinion, but all are agreed as to the ne-
cessity of obtaining results which may
be accepted as authority alike by manu-
facturers, builders, and engineers. This
could be accomplished either by the ap-
pointment of a special committee, similar
to the one created under the law of
March 4th, 1875, with an adequate ap-
propriation to purchase materials and
make a comprehensive series of tests ; or
failing in this, a moderate sum of money
might be placed at the disposal of such
an institution as the one under whose
auspices we are now assembled, to be ex-
pended in testing such constructions as
would be furnished from time to time by
engineers and others in their regular
practice, with the understanding that all
information thus obtained should become
public property by regular publication in
the Transactions of this and kindred so-
cieties. Could we feel assured of the
permanence of a special commission, the
members of which could devote the nee-

is OF MATERIALS FOB STRUCTURAL PURPOSES.

181

essary time to the work, this would doubt-
less be the must satisfactory to a large
majority of those interested.

There are uncertainties, however, con-
nected with all such special legislation in
a government constituted as ours is, that
should he carefully considered in this
connection lest we should be compelled
to undergo a similar experience to that
which befell the previous board, which,
from no fault of its own. was brought to
an untimely end after having perfected
the means by which, for the first time,

illy accurate testing could be done in
this country.

It is to be hoped that eventually a De-
partment of Public Works will be insti-
tuted, having a co ordinate power with
other departments, as of the Interior,
for example, to which all questions re-
lating to the expenditure of public
money, either for internal improvements
or for scientific investigations connected
therewith, may be referred, and through
which the interests of the producing
classes, including engineers, builders,
and manufacturers, may receive that spe-
cial consideration which their impor-
tance demands.

Whatever method may be adopted will
be liable to defects as a matter of course.
AVe must be content to go slowly and
surely, to be patient and judicious in ad-
vocating our claims, and above all to
bear in mind that if our cause is a good
one, as we believe it to be, and we do
not succeed in impressing its importance
upon Congress, it will, in all probability,
be our own fault.

REMARKS OF GENERAL MEIGS.

I do not know that I can do any more
than to express my entire concurrence
in the views which have been already ex
pressed by Mr. Macdonald. It appears
to me that he has gone over the whole
subject. I might add in regard to ap-
pealing to the government for an appro-
priation, that the government itself is
the largest single user of these materials ;
the railroads together use more, but
there is no single organization which
uses so much. Congress appropriates
the money with which are builded the
large government structures that are
found now in almost every city. It is
stated in the public press that it is con-
templating the erection of a 'hundred

new government buildings in a hundred
cities this year. In all these buildings
the floors are supported upon rolled iron
beams, and the principal materials used
for roofs are iron. These buildings are
all dependent for their cost upon the
size of their dominant members, and, as
a consequence, upon the factor of safety
which the engineer allows; so that as
[ long as there is uncertainty as to the
proper coefficient of safety, perhaps from
two to five times as much metal as is
actually necessary may be put into these
members. There are other materials
used in buildings, — brick, stone, marble,
timber, — but these materials we buy by
the cubic yard or cubic foot, they are
comparatively inexpensive ; metal we buy
by the pound and at this time we pay
pretty high prices for the pound; so that
if we can reduce our general coefficient
of safety, we save perhaps one-half to
two-thirds of the actual cost of the ma-
terial used. Congress sits under a roof
of iron, its building is crowned by an
iron dome; it is about building a new
navy and is considering whether it shall
be of steel or of iron, and the result will
depend upon the comparative qualities
of steel and iron. I see it stated by a
gentleman, eminent in the actual prac-
tice of steel making, that his company is
prepared now to furnish steel which
shall be guaranteed a tensile strength of
60,000 pounds to the square inch, with
30 per cent, elongation. One can hardly
imagine a more admirable metal.

Therefore I think that this society can
with a good heart go to Congress, and if
they can only convince some of its lead-
ing members of the necessity of more
knowledge on this subject, it appears to
me they must meet with success.

REMARKS OF MR. T. C. CLARKE.

The history of iron construction in
this country well illustrates the three
phases of thought described by Auguste
Compte, the French philosopher.

The first is the era of faith, when be-
lief in the safety of structures rests on
the authority of the designer. The
second is the era of criticism, when plans
of structures are analyzed with much
mathematical skill, but the data upon
which the chain of reasoning depends is
assumed upon insufficient experiment.
The third, upon which we are now enter-

182

van nostrand's engineering magazine.

ing, is a scientific era which demands
experimental proof. It also demands
that this proof shall be derived from ex-
periments made on full- sized specimens,
such as are in actual use, and not upon
toy models.

Until the construction of the United
States testing-machine, now at Water-
town Arsenal, it was impossible to make
such experiments with accuracy. We
now have a machine in which we can
test full sized specimens of every part of
a bridge or other structure that we want
to use, and under the same conditions in
which it is actually used. The next
thing is to get money to make these ex-
periments available. No private indi-
viduals can afford to do it, and even if
they could, they might wish to keep the
results to themselves. So that the next
point is that we want money, and that I
believe everybydy thinks we should ask
Congress for it. We want also, as has
been said, some one who shall make a
business of testing, and who has plenty
of time. Persons who are employed in
private business are too much in a hurry,
they want to do a thing and get done
with it, and then do something else ; but
government officers are entirely free
from this feeling ; time to them is of no
account, and in experimenting that is
the very element that is of value ; it does
not do to be hurried ; the great thing is
to get it right and to test your results,
and go over it again and again. And
the experimenter who operates the ma-
chine must be some person educated up
to the use of it. We then want a gen-
eral advisory board who will indicate a
plan of experiments, collect the results,
and publish them. Some experiments
were made the other day at the Water-
town Arsenal upon full- sized Phcenix
columns. Any one can see at once that
these are very valuable experiments, be-
cause we have certain columns all of the
same quality of metal, the same work-
manship, and the same cross-sections,
and differing only in length. As far as
these columns are concerned this would
be all, but it would then suggest itself
that we make experiments with the same
columns alike in other respect but with
different cross-sections, and then test
them made of steel, and so on. The
engineer is often asked why don't you
use steel? We can't expect to know

anything about it at all until experi-
ments are made in the way that I have
indicated in some such machine as this.
I venture to say that Messrs. Fowler &
Baker, who expect to build the great
bridge over the Firth of Forth, in Scot-
land, cannot find out anything about the
strength of the parts of their structure,
unless they have a machine equal to our
government machine. Then, the last
thing of all, after having made the ex-
periments, they ought to be published
monthly and sold in all book- stores.
Then every engineer could get a report,
and would have questions to ask and
suggestions to make, and would at once
write to the board and give them the
benefit of his thoughts. These sugges-
tions would be one of the most valuable
results of prompt publication.

REMAKES OF MR. O. CHANUTE.

In discussion of Mr. Macdonald's
paper, I can say little more than to add
to the general acknowledgments of ig-
norance, and like several of the gentle-
men who have preceded me, make one
of those confessions which are thought
to be good for the soul.

Having had some experience in the
erection of bridges during past years, I
am aware that we yet need much infor-
mation in order to proportion them to
the best advantage.

I would more especially like to empha-
size three of the points mentioned by
Mr. Macdonald, as among those upon
which we lack knowledge; these are:
first, the behavior of steel : second, the
proportions of compression members ;
and, third, the influence of the size of a
bar upon its strength per square inch.

First, as to steel. While we all ac-
knowledge this as the material of the
future, our position may be said to be
still one of expectancy. Few engineers
are bold enough to employ it largely in
bridges, and those who do, find such
serious difficulties in obtaining uniform
grades of it, are so puzzled by apparent
anomalies and unexpected phenomena,
that it requires considerable faith and
courage to apply it in large structural
masses. A series of systematic experi-
ments, such as have been partially made
by various European nations in their
government shipyards and elsewhere,
by which we should be enabled to con-

TESTS OF MATERIALS FOR STRUCTURAL PURPOSES.

183

nect the influence of the chemistry of
steel and of the process of its manufac-
ture, with results of the various modes
of working the product into its final
shape, would doubtless add so largely to
our knowledge of modern structural
steel, as to make reasonably clear much
that we now only suspect, and give us
the necessary knowledge and confidence
to avail ourselves of the increased
strength and economy which this metal
promises. At present we know that the
strength exists, but we also know that
steel is brittle under many conditions;
and where human lives are at stake,
where failure would involve such dis-
astrous consequences, we dare not avail
ourselves of the strength of that metal,
unless reasonably sure that it will not
break.

Secoiid, as to compression members of
structures. They are now proportioned
upon formulas which were framed many
years ago in England, and which were
based upon very few experiments, some
thirty in number, if I recollect rightly.
Not only were those experiments tried
upon pieces materially smaller, and of
different shape from those which we now
generally use, but they were made with
English irons, which are found to differ
in some respects from the characteristics
of American irons. We have accordingly
made some changes in the constant nu-
merical factors of the formulas, to at-
tempt to adapt them to our use, but we
now find from the experiments recently
made at Watertown with the govern-
ment machine, for Messrs. Clarke, Reeves
& Co., that even the modified formulas
are erroneous, and do not agree with the
actual condition of affairs. In fact there
is great uncertainty as to the actual
strength of the bridges which we are
now daily erecting. Their strength is of
course limited by that of the weakest
part, but while we endeavor to make
every part equally strong, as well as we
know how, yet we are almost entirely
ignorant as to what is actually the weak-
est part of a bridge of any magnitude,
and of just where it would give way first,
if loaded to rupture.

While no man knows exactly what
weight will crush flat, say a 4-inch cube
of wrought iron, we do know that it be-
gins to yield, without recovering its
shape, at pressures of some 36,000 to

40,000 pounds to the square inch. Ac-
cordingly, with the aid of the formulas I
have mentioned, we proportion compres-
sion members for an assumed crippling
point, varying from, say 35,000 pounds
to the square inch, for pieces of ten di-
ameters in length, down to about 24,000
pounds to the square inch for pieces
forty diameters in length, and upon these
we allow strains varying from 7,000 to
4,800 pounds to the square inch, as
working compressive loads ; while in ten-
sion we allow some 10,000 pounds to the
inch on iron, with a breaking strength of
46,000 to 50,000 pounds, and an elastic
limit of 26,000 pounds per square inch.
Now, in my judgment, the crippling
point of a compression piece corresponds
more nearly with the elastic limit in
tension, than with the ultimate or break-
ing strength. The probabilities of any
compression bridge member being
strained up to the crippling point, are
nearly as remote as the probabilities of
a tension member being strained up to
its elastic limit, and to have all parts
equally strong, should experiments justify
this view, we should base our assumed
margin of strength (you will note that I
do not use the term " factor of safety,"
as I think it misleading), upon the crip-
pling strength and the elastic limit of
the material. As for myself, I believe
that we are now making our compression
members considerably stronger than the
tension members ; that if we were to
break down a bridge by fair loading,
granting of course that all the connec-
tions should be made stronger than the
body of the pieces they attach together,
rupture would probably first take place
in one of the tension members. But
then while so believing, I do not know.
I confess my ignorance upon this point,
and until this ignorance is removed, I
shall go on specifying for proportioning
bridges in the old way, and with the old
formulas.

Third. Not only is there great uncer-
| tainty concerning the actual strength of
i compression members, but we do not
I know accurately the strength in tension
of full- sized bars worked to various di-
! mensions and with a different amount of
pulling and squeezing in the rolls.

In the bridge specification of the New
York, Lake Erie and Western Railroad,
we require that full- sized pieces of flat,

184

van nostrand's engineering magazine.

round or square iron, not over 4J inches
in sectional area, shall have an ultimate
strength of 50,000 pounds per square
inch, and stretch 12^- per cent, in their
whole length, while for bars of a larger
sectional area than 4J inches, we allow a
reduction of 1,000 pounds per square
inch, for each additional square inch of
section, down to a minimum of 46,000
pounds per square inch. This was
adopted after consultation with various
manufacturers of iron, who had large
experience ; but the discrepancies be-
tween the data which they furnished, and
the views which they expressed when the
proofs of the specifications were sub-
mitted to them, showed clearly that they
did not agree as to results, and that
they too were in need of further experi-
ments upon full-sized members of various
dimensions.

In the government machine at Water-
town, we have for the first time in this
country, a machine adequate to obtain
correct results upon full-sized members.
It has a capacity of 400 tons, while
former machines at various bridge works
had a capacity of only 150 tons, and
could not be trusted to w<5rk accurately,
to even 100 tons. Tension members
being composed of several parallel bars,
could be tested in detail, provided the
dimensions of the bars did not exceed
say 8 inches by 1 inch, but compression
members, with a sectional area of say 12
to 20 square inches, could not be tested
at all, and resort had to be had to small
models, which, as already stated, are not
found to give the same results as full-
sized pieces.

Tests are made for two purposes ; first,
to ascertain the best form in which the
metal can be placed to resist the strains ;
and, second, to ascertain the quality of
the metal itself. Upon the latter point
experiments are being made every day
by manufacturers, bridge builders, and
corporations which are erecting struct-
ures. Every time we contract for a
bridge we test many specimens of the
materials which go into it, and the cor-
poration with which I am connected has
tried hundreds of experiments upon the
quality of the metals it has used, which
will be very much at the service of a
testing board, should one be appointed.
These experiments have been carried as
far as we had any interest, that is to say,

to the point of ascertaining the quality of
the metal furnished ; but we have pre-
served many of the specimens, and a
testing board could ascertain the chemi-
cal constitution of each, and, perhaps, be
enabled to connect the various behavior
of the specimens with their chemical
characteristic and the process of their
manufacture.

For information as to the best forms,
however, we must rely upon the govern-
ment machine, and especially upon
government aid, as no single firm or
corporation has sufficient interest at
stake to warrant it in planning and pay-
ing for the great cost of a systematic
series of experiments, to ascertain what
are absolutely the best shapes into which
to put the members (chiefly those of com-
pression), by testing full-sized pieces.
Moreover, if any firm or corporation
were to become possessed of information
which is so much needed, it would prob-
ably endeavor to give it commercial
value, and to recoup its expenses, to say
the least, by keeping such information
for itself as long as it could, and the
general public of metal users would re-
main in its present ignorance.

It seems to me, therefore, that the
general government is the proper party
to institute and carry out the needed ex-
periments, not so much because, as has
been claimed, the materials to be tested
are "American" iron, steel, and other
metals, but because there is need of
general information, which no single
other party is likely to obtain and make
public. The government has the ma-
chine, it has abundant resources, and
the manufacturers and engineers of the
country, with universal go©d will, stand
ready to tender their aid and technical
knowledge.

Now one word as to the organization
of the inquiry and the doing of the work.
There should be some general plan of
operations, and this would probably be
best evolved by the deliberations of a
commission, but the actual work will be
chiefly done, as I think, by one man,
that is to say, by the man who may be .
placed in general charge of the experi-
ments, and whose duty it will be (to
draw an analogy from industrial organi-
zations) to act as chief executive officer,
or superintendent if you will, and to plan
and draw deductions from the various

THE DNIVEBBAL THEOREM.

185

needed experiments. The commission,
if commission there be, may lay out the
general plan, but it must have some one
head in charge of the actual carrying of
it out.

But how shall we secure the selection
of the very best man to put into that
position? He may be appointed in many
ways. He may be selected by the Presi-
dent of the United States, or by the
Secretary of War, or by the Secretary of
the Navy, or by the head of one of the
government bureaus, or by the commis
sion which has been suggested, and which
would thus act (to refer again to indus-
trial organizations) as a board of direc- j
tors or trustees. It does not, in my !
judgment, make much difference how he
is selected, provided we get the right I

man. A mistake may be ma le at first,
and changes may have to be made, until
the right man, a man like Kirkaldy, in
England, is brought forward, who shall
possess the necessary technical skill, the
executive ability, and the high standard
of accuracy and thoroughness to con-
duct the experiments, as well as the
talent to deduce general conclusions
from them.

Upon the whole, I believe that the best
way of selecting such a man, would be
through a board of commissioners. This
plan has been found to work best for
joint- stock companies carrying on large
operations, and I hope that Congress
will organize the work through a com-
mission as prayed for in the memorial of
the Society of Civil Engineers.

THE UNIVERSAL THEOREM,*

FOR THE INVOLUTION AND EVOLUTION OF POLYNOMIALS.

By GEORGE H. JOHNSON, B.S.
Contributed to Van Nostrand's Engineering Magazine.

That mathematicians have recognized
the need of a general theorem for raising
any polynomial to any power, is evident
from the various attempts which have
been made to find an easy method of
writing the powers of polynomials, with-
out using the tedious process of multi-
plication. The tables of numerical coef-
ficients which have been obtained em-
pirically ; the general term in the expan-
sion of the nth power of any polynomial,
as given by Todhunter, Hackley, and
others ; and the adaptation of Arbogast's
theorem to algebraic involution as given
by Galbraith and Strong, show what has
been done in this direction. That these
attempts have not been sucessful in at-

* The following extract is taken from the report of
the committee who examined the theorems:

New Brunswick, N. J., June 19, 1882.

The Knickerbocker Prize for Original Research
has been awarded to George H. Johnson of New
Brunswick for his paper on " The Universal Theo-
rem ." The subject is one which has exercised the
powers of the ablest mathematicians, and the ac-
complished expert who examined it says that "it is
clear and complete, and no doubt is entirely original.
The theorem is given a convenient form for practical
work, both as a formula and a rule. It is a general
theorem of which Newton's Binomial Theorem is a
particular case. I regard it as a very highly meritori-
ous production."

Geo. H. Ccok, William J. R. Tayor,

David D. Demorbst, Committee.

taining simplicity and utility is evident
from the fact that no reference is made
to them in many standard treatises on
Algebra.

After careful study I have deduced the
laws of formation of the ntn power of
any polynomial, and have expressed them
in a theorem which is both simple and
explicit.

1 believe that a brief examination is
sufficient to show the decided superiority
of this method.

Great simplicity is attained by arrang-
ing the answer in the form of an entire
function, as the coefficients are repeated
as many times as there are terms in the
given polynomial. It will be seen by
examining different examples that the
use of the theorem saves about 75 per
cent, of the work of multiplication, and
about 50 per cent, of that required
when substitutions are made in the bi-
nomial formula. When the polynomial
contains a large number of terms, or the
power is high, the advantage in using the
Universal Theorem is even greater. Sup-
pose that we desire the fourth power of
a polynomial containing ten terms.

The required expansion contains seven
hundred and fifteen terms, which may be

186

VAN NOSTRAND'S ENGINEERING MAGAZINE.

written down immediately by using the
theorem. If worked by multiplication,
taking the square of the square, we must
use three thousand nine hundred and
seventy terms. If we use the Binomial
Theorem we must make eight substitu-
tions and use over two thousand terms.
In this case we see that the Binomial
Theorem saves less than one-half of the
work of multiplication, whereas the Uni-
versal Theorem saves nearly five-sixths
of the work.

I have used the same method to dis-
cover the theorem which Sir Isaac New-
ton used to obtain the Binomial Theorem.
That is, I have compared a great many
developed powers in order to discover
the laws of formation. I have denomi-
nated the theorem " Universal " because
it may be applied to the involution and
evolution of any algebraic expression.
From the Universal Theorem may be de-
duced an infinite number of special
theorems. Indeed, we may deduce from
it several series of theorems, each series

containing an infinite number of special
theorems. As the first case, we have the
expansion of any binomial to the ntn
power, which is Newton's Binomial
Theorem. We may obtain in the same
way trinomial and quadrinomial theo-
rems.

We may have a second series for raising
any polynomial to any specified positive
integral power; for example, to cube
any polynomial.

We may have a third series the same
as the preceding, except that the expo-
nents of the required powers are nega-
tive. Finally, we have two more series
in which the exponents of the required
powers are positive and negative frac-
tions. By making the exponent of the
required power, minus one, I have ob-
tained a theorem for writing the recipro-
cal of any polynomial. I have also made
several numerical applications of the
Universal Theorem, and have thus found
an abridged method for obtaining the
squares and cubes of numbers.

STANDARD MEASUREMENTS.

By GEORGE M. BOND, Hartford, Conn.
Transactions of the American Society of Mechanical Engineers.

The subject of standard measurements
is not a new one, though it has received
the attention of minds well qualified to
master it ; still, the lack of a definite
system of uniform sizes for general use,
especially in machine construction, led
to the appointing of a committee by the
Master Car Builders' Association to se-
lect some one prominent firm engaged in
tool-making, to undertake to furnish
standard United States, or " Franklin
Institute " thread screw gauges.

The choice fell to the Pratt & Whitney
Company, of Hartford, Conn. ; and in
order to commence aright, the services
of Professor W. A. Rogers, of Harvard
College Observatory, Cambridge, were
enlisted for the purpose of obtaining an
exact transfer from the British Imperial
Yard, thus enabling the company to feel
assured that the " bottom " had been
reached, and to do, once for all, and for
the benefit of all, what seemed absolutely
necessary for a correct beginning.

The necessities growing out of the
difficulties of subdividing the yard, and
of applying such subdivisions in prac-
tice, led to the construction by them of a
comparator, of the form which Professor
Rogers found best adapted to compari-
son of standards. Two of these com-
parators, or "measuring machines," have
been made ; one to be placed in position
at Harvard College, and the other to
remain at the works of the company for
use in future comparisons.

It is- not the intention in the present
paper to give an exhaustive report, or a
detailed account of the condition, at this
late day, of the question of standards of
length, but simply to furnish, in a brief
and general way, such facts and state-
ments regarding the subject as are of
importance to those interested in the
adoption of a uniform standard of size
in the manufacture of tools and machin-
ery requiring inter changeability of parts,
and to show in what the standard for the

STANDARD MEASUREMENTS.

187

basis of future measurements consists,
and the method adopted for determining
how closely in practice such standard
measurements may be applied.

As is well known, three natural units
have been proposed as the basis of
standards of length, as follows :

I. The length of a pendulum beating
seconds in a vacuum, at the level of the
sea, in the latitude of London.

II. One ten-millionth part of the
quadrant of the earth's circumference.

III. The length of a wave-length of
given refrangibility.

The first of these natural units was
found to be unsuitable for the accurate
restoration of the original British Yard,
rendered useless by the great fire, Octo-
ber 16th, 1834, which destroyed both
houses of Parliament, where tlie stand-
ard had been kept.

Sir Francis Baily, Bessel, Kater, and
Dr. Young found serious errors affecting
the comparisons originally made between
the bar marked "Standard, 1760," and
the exact length of a pendulum beating
seconds under the above conditions.

It may be interesting to here insert
the act legalizing the standard :

"Section 1. Be it enacted .... that from
and after the first day of May, one thousand
eight hundred and twenty-five, the straight
line or distance between the centers of the two
points in the gold studs in the straight brass
rod, now in the custody of the clerk of the
House of Commons, whereon the words and
figures "Standard Yard, 1760," are engraved,
shall be, and the same is hereby declared to be,
the original and genuine standard of that meas-
ure of length or lineal extension called a Yard ;
and that the same straight line or distance be-
tween the centers of the said two points in the
said gold studs, in the said brass rod, the brass
being at the temperature of sixty-two degrees
Fahrenheit's thermometer, shall be, and is
hereby denominated the Imperial Standard

Yard.

******

"Sec 3 And whereas it is expedient that
the said Standard Yard, if lost, destroyed, de-
faced, or otherwise injured, should be restored
to the same length by reference to some inva-
riable natural standard; and whereas it has
been ascertained by the commissioners appoint-
ed by His Majesty to inquire into the subject
of weights and measures, that the said Yard
hereby declared to be the Imperial Standard
Yard when compared with a pendulum vibrat-
ing seconds of mean time, in the latitude of
London, in a vacuum at the level of the sea, is
in the proportion of thirty-six inches to thirty-
nine inches, and one thousand three hundred
and ninety-three ten -thousandths parts of an
inch.

"Be it therefore enacted and declared, that
if at any time hereafter, the said Imperial
Standard Yard shall be lost, or in any manner
destroyed, defaced, or otherwise injured, it
shall and may be restored by making a new
Standard Yard, bearing the same proportion to
such pendulum as aforesaid as the said Impe-
rial Standard Yard bears to such pendulum."

In view, therefore, of the errors due
to the doubtful reductions of the level of
the sea, and the estimated specific grav-
ity of the pendulum employed, and also
to other important factors, shown conclu-
sively by Dr. Young, Kater, Bessel, and
Baily, to be unreliable, the method
adopted and employed in restoring the
Imperial Yard, was to use standards
which had previously been compared
with it.

The bars available for this purpose
were:

(a.) Shuckburgh's scale (0 — 36 inch-
es).

(b.) Shuckburgh's scale, with Kater' s
authority.

(c.) The yard of the Royal Society,
constructed by Kater.

(d.) The Royal Astronomical Society's
brass tubular scale.

(e.) Two iron bars, marked A, and A,,
belonging to the Ordnance Department,
and preserved in the office of the Trig-
onometrical Survey.

The restoration of the standard was
intrusted to Sir Francis Baily, but his
death occurring soon after, the work of
restoration was committed to the Rev.
R. Sheepshanks. Baily had, however,
made numerous experiments regarding
the proper material to be used, and that
now adopted is known as Baily' s metal,
the composition of which is : copper, 16 ;
tin, 2.5 ; zinc, 1.

The mean of all the observations
taken, in comparing these available
standards, led Sheepshanks to assume
that "Brass Bar 2," the name given to
the working or provisional standard em-
ployed in his investigations, was equal
to 36.00025 inches, in terms of the lost
Imperial Yard, at 62° Fahrenheit.

The Imperial Standard Yard, known
as "Bronze 19," or as now denominated
" No. 1," was then constructed according
to this equation. It was made of Baily's
metal, and of the following dimensions :

Length, 38 inches ; width, 1 inch ;
depth, 1 inch.

Gold plugs are inserted in wells sunk

188

VAN NOSTRAND'S ENGINEERING MAGAZINE.

one-half the depth of the bar. The
graduations are upon these gold plugs.

"Bronze No. 1" is the national stand-
ard yard, and is kept in what is known
as the " Strong Room " of the Old Pal-
ace Yard, in London.

Besides this bar, four Parliamentary-
copies were made, one copy being kept
in the Royal Mint, one in charge of the
Royal Society, one at the New West-
minster Palace, and the other at the
Royal Observatory at Greenwich. Of
the forty copies prepared of Baily's
metal for distribution to foreign govern-
ments, only two are exactlv standard at
62° F.,— " Bronze 19 " and"" Bronze 28,"
— " Bronze 28 " is kept at the Royal Ob-
servatory, as an accessible representation
of the national standard.

All the other copies have the tempera-
ture, at which they are standard, marked
upon them.

In 1856 " Bronze Bar No. 11 " was
presented by the British Board of Trade
to the United States ; at that time it was
declared to be standard at 61.79° F.
According to recent comparisons this bar
is now .000088 inches shorter than the
Imperial Yard No. 1.

In reproducing a standard bar, whether
for reference, or as a working standard,
line or end, measure, or both, care must
necessarily be taken to know positively
that the surface, upon which the lines
are ruled, is a plane surface, in other
words, to avoid the slightest amount of
flexure, which would obviously vary the
distance between the lines, especially
when these lines are upon the outer sur-
face of the bar, and hence, in supporting
a bar, the points of support have been
found by Sir George Airy to be the dis-
tance apart represented by the formula :

Length.

Vws-1
being the number of supports.
"When there are two supports this form-
ula gives 10.39 inches for the distance
between the supports in the case of the
yard bars, and 28.87 centimeters in the
case of the meter bars.

Placing the gold plugs at the bottom
of the wells, sunk half-way into the
bronze bar, was intended to overcome
the difficulty of flexure, as the lines
would then be at the best plane of varia-
tion caused by flexure, still, by placing

the bar upon supports in such a way as
to neutralize this tendency of bending,
and having the surface carefully worked
to a plane under a microscope of a high
power before the lines are ruled. This
difficulty is removed if the lines which
are subsequently traced remain in focus
throughout the entire length of the bar.

Professor Rogers' method of using a
mirror surface of mercury as a reference
plane for working the guiding surfaces
or "ways," on which the microscope
plate slides, is that adopted, and the use
of a microscope of high power gives a
very accurate result, the perfect focus
obtained along the entire length of the
mercury trough, proving conclusively
that the microscope plate moves in a
true plane.

In the new comparator constructed by
the Pratt & Whitney Company, under
the direction and from plans suggested
by Professor Rogers, the means for over-
coming objections and difficulties arising
from errors due both to horizontal and
vertical curvature, deflection, etc., are
f ally provided for.

The plan adopted for securing accurate
sliding motion of the microscope plate is
perfect line-bearing, and the uniform
pressure is due to gravity simply, and
the bearing surfaces, or guides, are such
that errors due to imperfect straight-
line action may easily be remedied.

The flexure of the guides is also pro-
vided for by supports placed at about
one quarter the distance from each end
of the guide-bars, which are heavy hard-
ened-steel tubes, ground perfectly true
and parallel, using counter- weights to
overcome the flexure arising from their
own weight and the weight of the mov-
ing microscope plate.

The bars used as standards by the
Pratt & Whitney Company comprise :

I. A bronze bar of Baily's metal, hav-
ing lines ruled on sunken gold plugs.
It is a yard measure, with subdivisions
into feet only. This bar is designated in
the official report as "P. & W,."

II. A bar of Baily's metal, identical in
composition, and having the same section
as " P. & Wj." It is 42 inches long, and
has lines ruled on the surfaces of plugs
carefully inserted, made of an alloy of
platinum and iridium ; these plugs are
-fa of an inch in diameter, and are pol-
ished to a mirror surface. This bar has

STANDARD MEASUREMENTS.

189

lines representing the yard at G2° Fahr-
enheit, with subdivisions to feet and
inches, and the meter at 62° Fahrenheit.
The alloy of platinum and iridium
gives clear smooth lines when ruled with
the finest diamond edge, and in order to
prevent accidental defacing, or injury
from any cause, the lines are covered
with disks of glass y-J-^ of an inch thick.
This bar is denominated, in the report,
" P. & W2."

III. A yard and meter bar, of hard-
ened steel, on the upper polished surface
of which are ruled lines corresponding to
those upon " P. & Wt," but having, in
addition, end measure for the yard at
62° F., and for the meter at 32° F.

The neutral points of support, i. e.,
those of least flexure, are left as " spots "
on the under side of this bar, so as to
avoid mistakes due this cause when in
use. This bar is marked "P. & W,."

IV. A steel yard and meter bar, un-
tempered, but having the same form as
the preceding, the only difference being
that the yard and its subdivisions, and
also those of the meter, are ruled upon
the mirror surfaces of hardened steel
plugs, the end measure for the yard and
meter also being determined by plugs of
the same material, fitted in each end,
and protected from injury by an exten-
sion of the upper surface. This bar is
designated "P. & W4."

After the preparation of these bars at
the works of the Pratt & Whitney Com-
pany, they were forwarded to Professor
Rogers, at Cambridge, for the purpose
of receiving the graduations. An addi-
tional bronze bar, the exact duplicate of
"P. & W2." was also sent, on which a
provisional transfer of the yard from the
steel bar in his possession was made,
after applying the reduction to the Im
perial Yard given by Mr. Chaney, the
Warden of the Imperial Standards. This
provisional bar was then forwarded to
Washington, Professor Hilgard having
kindly consented to compare it with
" Bronze 11."

According to the report of Professor
Hilgard, this yard is .000025 inches
shorter than "Bronze 11."

The yards traced upon " P. & W," and
" P. & W2" were obtained from this pro-
visional yard. They were then sent to
Washington for final comparison with
"Bronze 11."

According to the official report of
Professor Hilgard, after allowing for the
known relation between " Bronze 11 "
and the Imperial Yard, " P. & W," is
.000053 inches longer than the Imperial
Yard, and " P. & W2" is .000036 inches
shorter than this unit.

The yards and meters upon the steel
bars were derived from "P. & W," and
"P. & W2" after the reduction of the
relative co-efficient of expansion between
bronze and steel.

V. A hardened-steel six-inch bar, one-
half inch square in section, having upon
its upper polished surface, lines ruled
four separate inches, also lines represent-
ing—counting from the end of the sec-
ond inch — the lengths corresponding to
the bottom diameters or "tap-sizes" of
the United States or Franklin Institute
standard screw-threads, from a quarter
inch to four inches.

Besides this band of irregular spaces
are ruled two inches in sixteenths and
two inches in twentieths of an inch ; also,
a band of two inches at twenty-five hun-
dred per inch, the latter being used in
the investigation of the irregular lengths
or "tap-sizes."

This six-inch bar was ruled at the
American Watch Factory, Waltham, upon
a dividing engine constructed by the
Watch Company, from designs furnished
by Professor Rogers, for his use in pro-
ducing standards of length. The accu-
racy of the settings, and the remarkable
freedom from error found, upon a rigid
investigation subsequently made, prove
the excellence of the workmanship in the
construction of the machine.

It having been found necessary to re-
graduate this bar to accommodate the
sizes for larger diameter thread-gauges
than was at first intended, a complete
new series of irregular lengths was made,
the new lines being ruled as nearly .001
inches apart as it was possible to set the
diamond.

Upon comparing results the variation
was found to be less than .00005 inches
from the constant interval between the
new and the old lines.

When it is considered that nearly four
weeks had elapsed since the original
ruling was done, and that the same set-
tings were used, the extreme accuracy of
the screw of this machine may be appre-
ciated.

190

VAN NOSTRAND's ENGINEERING MAGAZINE.

The lines upon this bar are less than
.000066 inches in width, the cross-line in
the eye-piece of the microscope being
usually brought to cover either the edge,
or the middle of the furrow made by the
diamond cutter.

End-measures of hardened steel of the
same brand as the hardened screw gauges
have been made from a quarter of an
inch to four inches, vary by sixteenths,
and corresponding to the lines upon the
six-inch bar. With this bar, the problem
of maintaining uniform sizes in actual
use is a very simple one.

The practical difficulties met with in
using microscopes of high power, where
extreme accuracy is necessary, render
the use of any form of reflector very ob-
jectionable, as the reflected image is
often distorted.

In the use of Tolles's illuminator, in
which a prism is inserted within the ob-
jective of the microscope, this difficulty
is obviated, giving sharply-defined lines
upon opaque surfaces, such as steel or
bronze, and especially upon the plugs of
platinum and iridium.

The two objectives used upon the com-
parator belonging to thfe Pratt & Whit-
ney Company were furnished to order
by Mr. B. B. Tolles, of Boston, and both
have this form of illuminator attached.

Beferring back to the second natural
unit for establishing a standard of length
— that of using the ten-millionth part of
the earth's circumference — the result of
the labors of a commission appointed by
the French Government was four iron
bars, the ends carefully ground until
exactly comparable with each other, and
each having the required length. One
of these original bars, bearing the stamp
of the commission, is now in the posses-
sion of the United States Coast Survey.
From these bars the present meter of the
archives was constructed.

Of the third and last unit proposed —
that of a wave-length of given refrangi-
bility — it is doubtful whether this as a
unit can ever be successfully adopted for
general use ; since the measurements of
wave-lengths for an entire meter vary so
much as to make the total length of a
yard or meter known to a far less degree
of accuracy than can be assigned to the
comparison of different standards.

In conclusion, then, whenever the yard
with its subdivisions is adopted as the

measure of length, the unit to which all
measures must be referred, is the bronze
bar deposited in the " Strong Boom " of
Old Palace Yard, London, and known as
the " Imperial Yard, No. 1."

I quote Professor Bogers's statement
regarding the existing metric standards :

"Wherever the metric system has been
adopted, either by legal enactment or by actual
use in the absence of definite legislation, the
platinum end -measure meter deposited in the
archives of Paris, is the only ultimate standard
of reference."

The method adopted for the accurate
subdivision of the yard and meter upon
the comparator of Professor Bogers's
design, is to compare the arbitrary or
trial divisions first, by finding their rela-
tion to each other, with a fixed distance
between immovable stops, and noting
the time-worn axiom, that " things equal
to the same thing are equal to each
other." The yard or meter being correct
in total length, the differences from the
mean form an algebraic sum, the value
of which is evidently equal to zero.

The micrometers for use in the stand-
ard work by the Pratt & Whitney Com-
pany were furnished by James Queen &
Co., Philadelphia, and bear the name of
" J. Zentmayer " as a guarantee of their
excellence.

The coefficients of expansion of both
the bronze and steel bars, tempered and
untempered, in the possession of the
company, have been carefully determined
by Professor Bogers, the investigation
covering a period of nearly two hundred
days, under every possible condition of
temperature, in air, and immersed in
water, and the changes due to differences
of shape or mass have been carefully
noted. The changes of temperature of
the bar must affect the mass throughout
uniformly, and ordinarily from six to
twelve hours is necessary to allow these
changes to be effected before the com-
parison is made, the temperature mean-
while having been kept as nearly con-
stant as possible.

I may add, in conclusion, that the
standards in the possession of, and used
by Professor Bogers, comprise :

(a.) A nickel-plated hardened steel
bar, the lines upon the nickel surface
having been compared directly with the
Imperial Yard by Mr. Chaney, Warden

A NEW DIRECT PROCESS.

191

of the Standards at London, during the
visit of Professor Rogers in England.

(b.) An end-measure Coast Survey yard
kindly loaned by the Stevens Institute
of Technology, of Hoboken, N. J.

The Coast Survey yard has been com-
pared directly with the " working " yard
of the Exchequer by Mr. Chaney.

(c.) A meter, line-measure, the lines
traced upon the middle surface of an
X -shaped copper bar, of small mass, this
form having been adopted by the Inter-
national Bureau of Weights and Meas-
ures.

This bar was traced for Professor
Rogers during his visit at Paris, in Feb-
ruary, 1880, by M. Tresca, and is signed
by him.

(d.) A steel end-measure meter, made
by M. Froment, of Paris, and declared to
be 8.43 mikrons (about .00033 inches)
longer than the meter of the archives.

As was mentioned at the beginning of
this paper the intention is simply to re-
port progress, and to show how far the

" vital " part of this subject of standard
measurements has been carried.

That part of the work which may be
regarded as completed is the determina-
tion of the entire length of the yard as
represented by the bars " P. & W," and
" P. & W2," since according to the report
of Professor Hilgard, the mean of the
two yards differs from the Imperial Yard
by a quantity less than the certainty
with which such comparisons can be
made, viz., .00001 inches.

All the work so far described has been
done with a comparator having some
faults in construction, and although the
errors due to imperfections have been
allowed for, still it has been deemed wise
to defer the publication of the full report
of Professor Rogers until all the other
measures have been verified by observa-
tions with the new comparator. It is
confidently expected, however, that no
errors of appreciable magnitude will be
found in the working six-inch bar, upon
which all the standard gauges depend.

A NEW DIRECT PROCESS.

From "Iron."

The following is the translation of a
report, by Professor Sarnstron, on ex
periments made on dephosphorization in
a charcoal furnace at Nyhamm, on the
Vesterbergslagen, one of the largest iron
deposits in Sweden. As is well known,
bar iron was in earlier times produced
from the ores by smelting with charcoal
in small stoves or furnaces, and although
the ores then used contained a consider-
able amount of phosphorus, this circum- !
stance did not affect the mechanical
properties of the metal, as most of the
phosphorus was absorbed by this process
in the slag. This process has been
termed, by the Swedes, Osmund, and, by
the Spaniards, Catalan smelting. Al-
though excellent iron was produced by
this method, it has, of course, given way
to the blast and puddling furnaces. The
reason of this is that in the old Swedish
furnaces (in certain respects an improve-
ment on the Spanish) the process was
intermittent ; it was necessary to heat
and reheat them for any small quantity
of iron charged, and to blow out and

refill the shaft each time. It is evident
that in this way a great deal of fuel was
wasted, while but a very small quantity
of iron was produced ; and we may sup-
pose that the desire to improve the
method gradually led to the now existing
mode of making pig-iron, which, as a
continuous process, naturally produces a
larger quantity of metal, whilst a con-
siderably smaller quantity of fuel is con-
sumed. In the blast-furnace it became,
however, necessary to make use of ores
containing only a small quantity of phos-
phorus, and thus " mountain " or mag-
netic ores which contained considerable
percentages were objectionable. There
is still, however, in certain parts of
America a method in use by which ores
containing a considerable quantity of
phosphorus can be utilized. This method
has been called " metal forging ; " but as
it is also intermittent, and takes place in
open furnaces, it neither properly utilizes
i the fuel nor returns an equivalent per-
| centage of iron, and has in consequence
| been found very costly, and therefore is

192

van nostrand's engineering magazine.

in use only under exceptional circum-
stances. It is clear that, if the process
of conversion takes place in a shaft, as in
a blast-furnace, without the temperature
becoming so great as to effect any coales-
cence or complete smelting, and the
mass is, at this stage, transferred in a
convenient manner to a hearth where the
further process of fusing the iron par-
ticles can take place, the process will at
once become continuous and direct, and
has the advantages of saving fuel and
removing any impurities in the bloom at
the same time. The furnace, during this
operation, can be kept closed, so that
reduction by the hot carbonic oxide pro-
ceeds continuously. The furnace at Ny-
hamm consists of a reduction shaft
connected with the hearths by small cul-
verts. These hearths can be closed, hav-
ing vertical dampers with holes at their
lower part, in order that the gases gener-
ated by the fuel may pass through the
shaft and thus act the part of gas in an
ordinary blast-furnace. The dampers
are balanced, and are therefore easily
raised and lowered, the culverts being
also furnished with single bricks, by
removing which the necessary repairs to
the furnace can be done, but which, at
other times, close the furnace. Should
it be desired to cut off the shaft from the
remainder of the furnace, this can be
done by a horizontal damper, which can
be drawn closely over the hole. The
operation of the furnace is as follows :
Charcoal and ore are charged in the shaft
in proper proportions, either by a special
apparatus or in the common way. The
ore will then, as it settles in the shaft, be
subjected to the same process of conver-
sion as in the ordinary reduction-zone of
a blast-furnace. In order to transfer the
spongy iron to another hearth, a hook is
passed through the upper working holes
in the dampers of the culvert through
which the operation of raking down is
effected in order to keep the hearth
always well filled with charcoal and iron
until the smelting is nearly effected ; but
when it is desired to remove the mass of
iron, the raking down is stopped, and
the bloom allowed to go down in the
hearth. It may then be easily broken
up when one of the dampers is opened.
During this operation one fireplace should
be kept charged, as the gas-pressure in
the furnace should always be higher than

the pressure of air from without, in order
to prevent all suction of air through the
open hearth.

As soon as the bloom is removed and
the hearth cleaned out, it is again closed
and refilled with charcoal and iron, by
raking down from the shaft as before,
and the blast turned on. In the same
way, the process may be alternated with,
the other hearths. The furnace which
was erected at Nyhamm consisted of a
reduction shaft, 16 feet high, with a
cubic diameter of 16 feet above and 18
below, made of fire bricks, and was 1J
feet wide ; it contained 302.4 cubic feet
charcoal. With this was connected a
hearth, the dimensions of which varied,
as they were altered considerably during
the progress of these experiments. The
fittings were made of bar-iron, and were
very similar to those used in the Lan-
cashire hearths. The dimensions were
as follows : Distance between upper rim
of tuyeres, 2 feet ; but in order to facili-
tate the extraction of the bloom, they
were made to slope an inch outwards,
being thus 2 inches less at the bottom.
From the back, which was perpendicu-
lar, to the front wall, the distance was 2
feet, with 3 inches slope outwards ; but
this distance may, perhaps, be somewhat
reduced. The depth of the hearth was 1
foot, and the moulds inserted an inch,
with a declivity of about 22 degrees, and
their width at the nozzle -J by J inch,
with the upper sides semicircular.

As only one furnace was erected, it
became necessary to have an additional
"koltern," or heating apparatus, which
was kept going to prevent any suction
of air whilst the bloom was removed.
In order not to obtain any metal before
the tuyeres until the furnace was fully
heated, about 9£ cubic feet of charcoal
were thrown into the hearth when the
bloom had been removed. The front
damper was then closed, and charcoal
and ore raked down from the shaft till
the hearth became nearly filled ; the
blast was then put on and the raking
down continued, according to appear-
ances in the hearth. When the slag
made its appearance before the tuyeres,
generally half an hour after the blast had
been opened, it was tapped in precisely
the same manner as in a Lancashire
furnace. No particular work in the
hearth was required, but when the tuyeres

A NEW DIRECT PROCESS.

193

could not be kept free during the set-
tling, it was found necessary to insert a
bar carefully through one of the front
dampers in order to ease the mass. This
was, however, avoided as much as possi-
ble, as the coalescence of the materials
was greatly accelerated by any stirring
in the hearth, and caused great loss of
iron in some instances. The smelting
was also imperfectly effected, the bloom
being irregular and covered with a slaggy
coating. This was particularly the case
when the action of the furnace was de-
fective, owing to the choking of the
tuyeres by unreduced ores, &c. When
the mass commenced to fill the hearth,
the slag became more heavy and porous,
and poorer in iron ; the raking down
then ceased. The blast was still con-
tinued until the hearth became suffi-
ciently empty to allow the breaking out
of the bloom without removing any fuel.
Towards the finish some work was done
in the hearth with the bar, partly to keep
the charcoal over the tuyeres, and partly
to fettle up the bloom. This was, how-
ever, effected after opening one of the
side doors. An advantage which is very
considerable as regards the practical
utility of this furnace is the great ease
with which the raking down is effected,
as well as any other operation which may
be required in the hearth whilst the blast
is on. For instance, when the furnace
becomes heated, the flame, which is forced
through the holes when these are opened,
is so u curt " and transparent that it is
quite possible to stand at a distance of 4
to 5 feet from the hearth and look into
the furnace whilst raking down charcoal
and ores without any inconvenience.
With a little practice, which an unskilled
laborer may acquire in a week's time, it
is possible to charge and rake charcoal
and ores uniformly down, an advantage
of great importance, as it embodies a
check whereby, to a certain extent, the
action in the furnace may be kept per-
fectly even.

The furnace was tended by one man
each shift, who, with the assistance of a
boy, stored the ores and charcoal and
also removed the slag and attended the
;'koltorn." As the hearth during the
process was closed, the flame could only
issue from the working-hole through
which the furnace was tended ; the heat
was therefore small, and as the work
Vol. XXVII.— No. 3—14.

consisted chiefly of raking down into the
hearth, tapping the slag, and keeping the
furnace clean, it may be said that the
actual labor of tending the furnace was
comparatively simple, both as regards
the labor involved and the skill required
It may be added anybody without ex-
perience in tending furnaces can be em-
ployed, and one may therefore be entirely
independent of the skilled workman, this
circumstance being no inconsiderable
factor in the method. The shaft was
capable of holding from twenty-two to
twenty-three charges of two barrels char-
coal each, viz., 290 cubic feet each smelt-
ing, and one smelting was generally
effected during twenty-four hours. In
most of the experiments two barrels —
12.6 cubic feet of charcoal to 3 cwt. of
ore — were used, but towards the finish
the quantity of ore was reduced to 2
cwt., i. e., to 1 cwt. per barrel of charcoal
(6.3 cubic feet), and this proportion was
found advantageous, both as regards ore
and the quantity of fuel consumed, in
proportion as the ores contain more or
less phosphorus. It would, however, be
better to keep the slag richer and more
plentiful in iron by a greater charging of
ore than otherwise, unless it should, of
course, be preferred to make the process
more basic by a flux of lime or alumina.
If such should be the case, it may be
pointed out that a flux of this kind would
be more effective in effecting dephos-
phorization than a refining furnace, a
result which is brought about by the
ferrous oxide contained in the slag ap-
pearing to act on the phosphorus in the
same manner as lime on sulphur.

The experiments which we record were
commenced in November and continued
till about the middle of December, and
then resumed with few interruptions from
! January to March. The results arrived
j at during this period were, of course,
variable, as the idea guiding these ex-
periments was to find the best relation
between the hearths, their diameter, the
number of the tuyeres, their size, inclina-
I tion, pressure of the blast, &c. We
shall, therefore, here only lay before our
readers those results which tend to show
what might best be effected with such a
furnace, the following being the particu-
lars of the working during the last few
S weeks. The ores used were unroasted
I iron ores from the Viifspols mine in

194

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

Granges berget, a famous iron deposit
in Sweden, and contained about 60 per
cent, of iron and 0.91 of phosphorus,
which were charged with 1 cwt. of ore
per barrel of charcoal, viz., 1 cwt. of ore
to 6.3 cubic feet of charcoal.

The results of the following five shifts
were :

Consumption of

Charcoal
Barrels.

1 day shift 23

1 " " 2^

1 " " 7

1 night shift 25

1 day shift 21

100*

= 633 cubic ft.

Ores.
Cwt.

Yield of
Iron.
Cwt.

11.40
. 11.60
. 4.00
. 10.65
. 10 80

48.45

As 12J of these 100^ barrels were con-
sumed in the fireplace, the actual quan-
tity of fuel used for iron-making was only
88 barrels, or 554.4 cubic feet, for the
smelting of some 88 cwt. of ores ; the
relative consumption being therefore
2.07 barrels, equal 13.04 cubic feet char-
coal and 1.80 cwt. ore per cwt. iron re-
turned. The actual returns of iron were
thus 55.05 per cent. It ought, however,
to be stated that the bloom returned was
not weighed separately, but in solid un-
broken blocks, and although these when
broken up, were found extremely com-
pact and free from slag, the result would,
no doubt, not have been so satisfactory
had the smeltings been mixed together,
just as they came from the hearths.
The reason why this was not done was
that they were at first too small and
loose for the big hammer, and when they
became larger and more compact, the
Lancashire smiths did not approve of
having their materials made impure by
these. The only thing to be done was
therefore to pile them up till a convenient
opportunity arose of having them re-
heated in the Lancashire hearth, and to
this end they were subsequently broken
under the crushing hammer, when there
was also a good opportunity of examin-
ing thefracture, which was generally found
somewhat coarse and crystalline, with a
finer surface, however, underneath and at
the edges, which could, no doubt, be ac-
counted for by the circumstance that
these parts had absorbed more carbon.

As a rule three hours were required to
smelt a mass of 3 to 4 cwt. It is, there-

fore, to be expected that the parts which
were the longest exposed to contact with
the charcoal had absorbed the greatest
percentage of carbon ; but with increased
dimensions of the shaft a more thorough
reduction, and therefore an increased
production would be effected. The prin-
cipal work of the furnace would also be
to smelt the iron particles effectually,
and the mass would not remain so long in
the hearth, on one side exposed to carbon
cementation, and on the other to the op-
posite effects of the slag and the blast,
thus tending to make the bloom uneven.
The effect of these are minimized in pro-
portion, as less time is expended in the
smelting, and in consequence a more
homogeneous product may be looked for.
Owing to the depth of the hearth and
the long time which was required for the
settling, the bloom became cooled under-
neath, which made it a work of some diffi-
culty to extract the slag at the notch.
This difficulty ought to be avoided,
either by heating the mass before it is
taken out, or by giving it an appropriate
heating in a separate " welding " furnace
before breaking it up. Should it be de-
sired to obtain through a resmelting
process a thoroughly homogeneous prod-
uct, this can of course be best effected
in a Martin furnace, by which excellent
castings may be obtained, even from
metal of inferior quality ores, and this
charcoal method might therefore become
a factor of considerable importance in
the Siemens-Martin process. In conse-
quence of the compactness and small
caroon contents of the blooms the proc-
ess of refining the Lancashire furnace
was very slow; in fact, there was re-
quired as much time as well as fuel to
effect the resmelting as to effect an ordi-
nary Lancashire refining. The loss was,
therefore, in this case greater than would
under other circumstances have been
justified ; and it should be at once
understood that the latter part of the
process can never be considered practical
or necessary, and it would on the other
hand be out of the question with a better
regulated working and action, a fact
which was fully demonstrated at the
crushing of some of the blocks.

The total quantity of iron made was
about 300 cwt., from which the following
analyses of the contents of phosphorus
were made :

A NEW DIRECT PROCESS.

195

PerCent.

Phosphorus

Iron from

Bjornhytte mine contained 0.02

> < 14

0.06

Vftfpolflgrufvan

0.12

t 4

0.10
0.12

<< «<

0.08

< •

< < i

0.10

The two latter were, however, from
blooms which were not resmelted. In
the crucible the Vafpols ore yielded 62.3
per cent, of pig iron, with 1.32 per cent,
of phosphorus. Three analyses of the
iron gave respectively 1.33, 1.48, 1.70 per
cent, of phosphorus, equivalent therefore
to 3.01, 3.37, 4.10 per cent, phosphoric
acid.

Under the tests made on the iron thus
manufactured, in order to ascertain its
tension, it did not show any tendency to
redshortness or brittleness ; and by the
experiments made at the testing estab-
ment at Liljeholmen on a rolled bar of
this iron, 600 lines long and 48 lines in
diameter, the limit of elasticity was
shown to be = 48 lb. per square line,
with a bearing strain =81 lb. per square
line with an elongation of 20.8 per cent.,
a result which, it must be admitted, is
very satisfactory, and can compare well
with the class of pig-iron made by the
Lancashire process. What was fully
borne out by the experiments at Ny-
hamm, and which promises well for the
further development of the method as a
charcoal reduction process, is the fact that
the action in the hearth, and conse-
quently the result, stood in direct pro-
portion to the temperature in the shaft,
i.e., to the reduction of the iron before it
fills the hearth. If the furnace was suf-
ficiently heated, no hard lumps, for in-
stance, could be noticed chafing the rod
when raking down, and the action was
then perfectly regular, the moulds were
clear, and the formation of slag small ;
whereas, when this was not the case, the
action became at once less satisfactory
in proportion as the temperature in the
shaft fell. As the temperature in a fur-
nace can be lowered, not only by exces-
sive charging, but also by an action which
is either too quick or too slow, &c, the
case was just the same in this instance,
and the effect analogous, viz., the unre-
duced metal remains in the slag in the
same proportion as the reducing capabil-

ity of the furnace decreases ; and as the
iron in the hearth is not overcharged
with carbon, besides appearing solid, no
boiling could possibly arise from the in-
fluence of the iron-charged slag on the
bloom ; but this circumstance, in addition
to the loss occasioned by unreduced iron
being absorbed in the slag, should have
caused further waste of metal. The
question here, therefore, as with all fur-
naces, is to carefully observe that the
charges, their quantity and composition,
as well as other circumstances directly
affecting the action of the furnace, are
all in accord with the object in view, al-
though it may be said that divergences
may in the present method not affect the
action of this furnace to the extent which
is the case with an ordinary blast fur-
nace from the same causes. At the same
time it seems from the practical experi-
ences gained from this method that any
overcharging of the shaft has an injurious
effect on the smelting. We also attach a
few particulars of some experiments with
the same method made at Soderfos by the
candidates at the Royal School of Mines
in Sweden. The shaft was in this case

16 feet high, and capable of containing
ten charges of two barrels, viz., 12.6
cubic feet each ; about half the quantity
therefore of the one erected at Ny-
hamm. The manufacture here was about

17 cwt. pig iron per shift, with a con-
sumption of 25.2 cubic feet charcoal per
cwt. pig, and about -J- cwt. ore per barrel
charcoal = 6.3 cubic feet. By the ex-
periences thus gained in the method, it
seems — whilst, of course, pointing out
the improvements and alterations which
might be effected for its simplification —
that it would be of practical utility as a
charcoal process for the direct conver-
sion of ores containing an unusually
large amount of phosphorus.

We may, in concluding this article,
state that the district of Vesterbergs-
lagen embraces the richest and purest
stratum of metalliferous mountain in
Sweden, and it is only to be regretted
that the quality of the ore is not equal
to those generally found in that country.
It contains close upon 70 per cent, of
pure iron, but as much as 1 to 1.50 per
cent, of phosphorus, which, with the
means at present at disposal, renders
them of little use for the manufacture of
steel. The metal from these ores is,

196

VAN NOSTKAISTTS ENGINEERING MAGAZINE.

however, largely used for castings, and
if the time be not far distant when the
charcoal supply of Sweden may fail to
satisfy the demand, and coals be required
for smelting, the deposit may become a
source of immense wealth to that coun-
try. Among the extensive iron deposits

in this district, the above-mentioned
Grangesberg alone contains a bed of iron
said to be nearly 15,000 feet long and
1,000 to 1,500 feet wide, consisting
partly of peroxide of iron and partly of
magnetic iron of volcanic origin ; the
gangue is quartz and apatite.

A NEW FORM OF VERNIER.

By H. H. LUDLOW, 2d Lieut. 3d Artillery, U.S.A.
Written for Van Nostkand's Engineering Magazine.

Verniers have been so extensively
used and brought to such perfection
that there seems to be but little room
for improvement. There are cases, how-
ever, in which a scale very similar in
principle is more advantageous.

Thus, suppose a main scale divided to
J- in., and an accompanying direct vernier
which reads to y^-g- in., the entire vernier
of 25 spaces will exactly cover 24 scale
spaces, giving a length of 6 inches.

Instead of the vernier, another scale
may be constructed as follows : Let x
denote the vernier space expressed in
inches. Assume

4 ou" — 10

00'

(!)•

whence £=¥\inch.

The new vernier or subscale is com-
posed of 25 spaces, giving a length of 2
inches. It is represented in the figure,

venient vernier of the ordinary form with
the same least count, would require a
smaller scale space and a greater number
of scale divisions.

It inight at first sight appear that the
coefficient of x in equation (1) may be
any whole number ; but in fact it must
be such that the second number of (1)
will exactly divide the value of x, other-
wise this second number will not be the
least count. For example, suppose

i-5x:

10 0

— 24-
TToT

JC =

T2T*

Then I— 26x:

0 0'

(2).
show-

ing that 26 subscale spaces differ by
inch from 5 scale spaces. The corre-
sponding subscale is direct, has a least
count of -g-J-g- inch, contains 125 subscale
spaces, and exactly covers 6 scale spaces,
giving an entire length of 1J- inches. It
would have its divisions too close to-

9 10 11 12 13 14 15 16

17 18 19 20 21 22 23 24 25

and is read in the same way as the ordi-
nary vernier. Subscale division num-
bered 7 is coincident and the reading is
10.07 inches. It gives the same ultimate
unit of measure as the above vernier
with J the length, replacing a vernier of
6 inches by a more convenient one of 2
inches. The numbering of the new ver-
nier is not consecutive. It is as though
the vernier first taken had been divided
into 3 equal parts which had been super-
imposed, thereby compressing it to J its
original size. To obtain an equally con-

gether to be seen distinctly without a
magnifier, and would not be convenient
in use. The divisions would be num-
bered with intervals of 26 subscale spaces
between consecutive numbers instead of
3, as in the figure.

The subject is worthy of careful con-
sideration by those interested in devices
for accurate measurement. In favorable
cases the new form procures accuracy
and convenience with a less number of
scale divisions, thereby diminishing the
cost of the entire instrument.

THE EDISON ELECTRIC LIGHT METER.

197

THE EDISON ELECTRIC LIGHT METER. *

Bt FRANCIS JEIIL.

The principle upon which this meter
is founded is known as electro-metal-
lurgy, that is, the disruption or tearing
away of a metal by electricity, from one
electrode and its deposition upon the
opposite.

FUNDAMENTAL PRINCIPLES.

If an electric current, no matter how
generated, whether by a dynamo ma-
machine, or voltaic element, be made to
pass by means of platinum electrodes
through acidulated water, electrolysis
takes place, that is, the current has
the power of loosening and separating
•certain chemical compounds — in other
words, it decomposes the compound
through which it has passed. Any sub-
stance which is susceptible of decomposi-
tion by an electric current is termed an
" electrolyte."

By the term electrodes is always un-
derstood the two extremities or poles
which lead from a source of electricity.

Electrodes are divided into anodes
and cathodes.

The positive electrode is called the
anode, and the negative the cathode.

The products of decomposition, or the
substances which gather at each pole
during electrolysis, are termed "ions."
That which gathers at the anode is called
anion, and that which gathers at the
cathode is called cation.

The amount of current required for
decomposition varies greatly with differ-
ent electrolytes.

In the above mentioned case, where
the current passes through acidulated
water, oxygen gas is liberated at the
anode, and hydrogen at the cathode.

If into this liquid which contains the
acid some crystals of sulphate of cop-
per (CuSot) be thrown, electrolytic ac-
tion will still continue, but in a different
manner, oxygen will be evolved, and cop-
per will be deposited on one of the
platinum electrodes, while the hydrogen

* ' I'nder the above title this article was originally
published in London in pamphlet form. For presenta-
tion to the scientific public such pails of the original
as pertained to the manipulation of the meter have
been omitted', but the complete exposition of the
principles upon which it operates are retained.

takes the place of the copper in the
solution. It may be represented chemi-
cally by H90 -f- CwS04 before the current
has passed, and 0 + Cw + H2S04 after the
current has passed.

If in the above experiment, a copper
electrode be substituted for the posi-
tive, it will be found that no gas will
be liberated, the hydrogen, as before,
will take the place of the copper in
the solution — the oxygen, instead of es-
caping at the anode, will combine with
the copper of the electrode and the
sulphuric acid, to form sulphate of cop-
per.

The chemical forces, called into ac-
tion by the current, are so beautifully
balanced, that in our last experiment
the quantity of copper, supplied by the
positive electrode, exactly equals the
quantity withdrawn from our solution
and deposited upon the negative elec-
trode.

LAWS OF ELECTROLYSIS.

The following were demonstrated and
discovered by Faraday.

Electrolysis cannot take place unless
the electrolyte is a conductor.

The energy of the electrolytic action
of the current is the same in all parts.

The same quantity of electricity — that
is, the same electric current — decomposes
I chemically equivalent quantities uf all
I the bodies which it traverses ; from
I which it follows that the weights of the
| elements separated into these electro-
| lytes are to each other as their chemical
equivalents. For instance, in the de-
composition of water it will be found
that for every 18 parts of water decom-
posed two parts will be hydrogen and 16
oxygen ; in order to form water from its
two component gases we must take them
in the above ratio.

It also follows from the preceding law
that the quantity of the substance which is
i decomposed is proportional to the total
quantity of electricity which passed
through it, and is independent of the
time during which the electricity passed ;
the quantity corresponding to the pas-
sage of one unit is called the electro-

198

VAN NOSTRANDS ENGINEERING MAGAZINE.

chemical equivalent of the substance.
Thus, when one unit of electricity passes
through a solution of sulphate of zinc,
having platinum electrodes, one electro-
chemical equivalent of zinc appears at
the cathode, and one electro-chemical
equivalent of oxygen at the anode, while
one electro-chemical equivalent of sul-
phate of zinc has disappeared from the
solution, but an equivalent of sulphuric
acid has taken its place. If, in the above
experiment, zinc electrodes were used,
the action would be as follows :

For one unit of electricity, one elec-
tro-chemical equivalent of zinc would ap-
pear at the cathode, one electro-chemical
equivalent of oxygen at the anode, there
uniting with the zinc and sulphuric acid
to form another electro-chemical equiva-
lent of sulphate of zinc, and taking the
place of the one just decomposed. This
action continues, and keeps on deposit-
ing zinc on the cathode, and taking zinc
off at the anode.

Upon the preceding law has Mr. Edi-
son based his meter, and no matter how
much current passes through it, for
every electrical unit or fraction (which
unit is called au Ampere),, there will be
a corresponding number of units or frac-
tion of a unit of the metal deposited.

POLARIZATION.

If, in a circuit consisting of an elec-
trolytic cell containing acidulated water,
having platinum plates for electrodes,
we insert a single voltaic element to-
gether with a galvanometer to measure
the current, we find that the strength of
the current. rapidly diminishes on closing
the circnit.

Neither oxygen nor hydrogen appears
in a gaseous form at the electrodes, but
the electrodes have acquired new prop-
erties, showing that a chemical action
has taken place at the surface of the
plates. If now the battery be discon-
nected, and the galvanometer alone,
with the electrolytic cell, remains in the
circuit, it will be found on closing it
that a current is traversing, and show-
ing on the galvanometer that it is in an
opposite direction to the original cur-
rent. This current rapidly diminishes
in strength and soon vanishes. It can
also be seen that this current is not as
strong as the primitive one. This ac-

quirement of the electrodes is termed
polarization.

In the construction of an electric
meter, such elements must be used as-
will not, under any circumstances, polar-
ize ; for suppose an electrolytic cell, which
was capable of being polarized was used
to ascertain the amount of current that
was passing through the line in which it
was inserted it would, in the first place,
have the tendency to weaken the original
current, and, if the instrument was
shunted, as is essential in electric light-
ing, this counter current would all the
while resist the original current, causing
an erroneous deposit, it depositing less
metal than would be deposited if there
were no polarization. Then, again, when
the current on the line ceases to flow,
this counter current would begin to act
and redeposit some of the metal which
the original current had deposited.
Thus we see why any elements capable of
polarization would not do for an accu-
rate meter. Then again, there is another
consideration that comes into play, and
that is, that nearly all elements when
immersed in a solution, generate a small
current, for example: Two plates of
copper in a solution of sulphate of cop-
per, when connected with a galvanom-
eter, will indicate the presence of a cur-
rent. Now, in the above case, when the
electrolytic cell was shunted it had nec-
essarily, a closed circuit. The circuit,
being closed, this current, as indicated
by the galvanometer in the last experi-
ment, would become active, and deposit
metal while there was no current circu-
lating in the line. This current, al-
though feeble, will in time deposit a con-
siderable amount of copper, and cause
an inaccuracy almost inconceivable. A
copper deposition cell, and some other
metals, is suitable for large currents,
and when the plates are taken out of the
solution, immediately after the current,
ceases to flow ; but when it is required
to register a very small current, such as

^ of an Ampere, and when the de-

100 0

position cell is always on a closed cir-
cuit, it becomes necessary to use some;
other metal than copper in order to ob-
tain accurate results.

In order to get rid of this difficulty of
polarization, Mr. Edison found that by
using electrodes of pure zinc, amalga-
mated with pure mercury and a solution

THE EDISON ELECTRIC LIGHT METER.

199

of chemically pure sulphate of zinc,
that there is almost no polarization, and
great practical accuracy is insured when
an exceedingly small quantity of current
is desired to be measured. The same is
true if the currents be of large dimen-
sions.

I may add that it is advisable in all
electrical researches, whenever it becomes
necessary to ascertain the magnitudes of
an unknown current, and especially if it
be small, that instead of using the copper
deposition method an electrolytic ele
ment consisting of pure zincs amalga-
mated with pure mercury in a chemically
pure solution of sulphate of zinc be
used.

RESISTANCE OF ELECTROLYTES AND METALS.

50c

showing a decrease of 1.08
tween the limits of 0° and 50°
remember that this difference is in

ohms be-
C. If we

con-

| trary direction to that of copper, it will
be seen that if we take a certain length
of copper wire which changes its resist-
ance between 0° and 50° by the same
amount as the solution but in the
opposite direction, that by placing the
two in series, that is in the same cir-
cuit with each other, one would com-
pensate for the other, that while one
diminishes the other increases, and the
circuit in which they are placed main-
tains a constant resistance and does not
vary with the temperature. Mr. Edison
has made use of these principles in his
meter, and has a constant resistance in
the circuit where the deposition cells are
placed, without which an electric meter
would be of no value where there is a

GENERAL DESCRIPTION OF THE METER.

It is very difficult to measure the elec-
tric resistance of some electrolytes on
account of the polarization of the elec-
trodes. In order to overcome this diffi-
culty one must use, as stated in the pre-
ceding article, zinc electrodes. There j change of temperature,
are other methods for ascertaining the !
resistance of solutions, but it is not nec-
essary for me here to explain such
methods. The temperature of the so-
lution greatly affects its resistance. It
will be found that its resistance decreases
as the temperature increases, or when
the temperature decreases the resistance
increases. Thus we see it has properties
similar to carbon, for carbon will de
crease its resistance when its tempera-

The meter is divided into two com-
partments. The first, or the one on the
left side, is termed the monthly cell.
This is taken out every month by some
employee of the company, and another
cell is substituted for it. The one taken
out is returned to the station, where the
plate that has received the deposition is

tore is increased and vice versa. These weighed. The cell on the right hand of
properties are just the reverse of those I the meter is termed the quarter yearly
exhibited by the metals. cell, and is a check cell. The party that

We, therefore, lay down the following j has access to the monthly cell has not to
laws, namely : I the quarter yearly cell. This quarter

That the . resistance of electrolytes yearly cell is taken out every three
diminish as the temperature increases. months and the deposit weighed. Its

deposit must bear a certain proportion
to the sum of the monthly meter de-
posit for those three months. If its de-
posit does not agree in proportion to the
monthly cell, there is something wrong,
or somebody has tampered with it.
Thus we see the object of this auxiliary
cell. In the diagram A is the monthly
cell, and A' is the quarter yearly cell.
B' and B are the compensating resist-
ances, in series with the cells A' and A
respectively, the object of which has
been explained.

The resistance of metals increases as
the temperature increases.

Now, it is obvious that, if we ascertain
the resistance of a certain solution at
different temperatures, we can ascertain
the difference of its resistance between
such temperatures. For example, if a
solution of sulphate of zinc at 0° C, and
specific gravity 1.29, offers a resistance
of 1.40 ohms, at a temperature of 50° C.
its resistance is diminished to 0.32 ohms.
Therefore, the difference between those
two temperatures is —

200

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

C and C are the respective shunts,
(made cf bands of German silver), from
which the cells A and A' receive their
current. In all meters, irrespective of
their capacity for registering, the resist-
ance of the cell A with its compensating
resistance B is 830 times the resistance
of the shunt C, and the resistance of A'
plus B' (equal to A plus B) is 3320 times

METHOD OF CALCULATION.

Whenever a meter is set up to register
the consumption at any place the weight
of the plates is recorded. The weight
of the plates from the monthly cell is
taken after they have been in use the re-
quired length of time, and upon the gain
in weight of one plate is based the

Qffi

._.j

Mill

]

AJ*

the resistance of C within the ranges of
temperature occurring in practice. The
resistance of C is therefore one-fourth
that of C and the cell A' will receive one-
fourth as much deposit as A.

D is a thermo arrangement which pre-
vents the freezing of the sulphate of zinc
solution in the winter, or too low a tem-
perature for accurate registration. It
consists of a strip of brass and steel
riveted together.

The unequal expansion and contrac-
tion of the two metals causes contact to
be made at F when the temperature falls
to the lowest desired limit to which F is
adjusted. This throws the lamp E in
circuit, the heat from which raises the
temperature in the meter, and acts upon
the thermo strip causing it to open the
lamp circuit.

amount of current used. The gain in
the quarter- yearly cell should, in the
given time, equal one-fourth the gain in
the monthly cell for three months.

It has been stated that the resistance
of the circuit containing the monthly cell
is 830 times the resistance of the shunt
around which it is placed, therefore of
the total current passing ^yst part will
pass through the cell and be registered.

If it is experimentally determined that
the ^-J-iSt part of an Ampere flowing
through the cell for one hour will de-
posit 1.6 milligrammes, then is this the
true indication of one Ampere for one
hour, because the remaining ff-J will
flow around the cell and through the
shunt without being registered.

To find the number of Amperes for
one hour, therefore,

ON VARIATIONS IN THE LIMIT OF ELASTICITY OF VARIOUS METALS. 201

Gain in milligrammes

Amperes flow-

1.6

ing for one hour.

This result may also be expressed as
" number of hours for one Ampere."

Tf one lamp, giving 16 candle-power of
light, requires a current of three-fourths
of an Ampere, the amount of deposit in
the cell in one hour for this lamp would
be three-fourths of 1.6 milligrammes =
1.2 milligrammes.

Therefore, to find the number of lamps
operating for one hour to produce the
deposit,

Gain in milligrammes
for one hour.

= number lamps

This result may also be expressed as
"number of hours for one lamp."

Thus the gain of weight in one plate
bears a constant ratio to the current
which has passed through under a uni-
form pressure, and also to the energy
consumed beyond the meter, and is
therefore a register of the amount of
energy, irrespective of the particular use
to which it was applied.

ON VARIATIONS IN THE LIMIT OF ELASTICITY AND IN
THE MODULUS OF ELASTICITY OF VARIOUS METALS.

By PROF. J. BAUSCHINGER.
From "Der Civilingenieur," for Abstracts of the Institution of Civil Engineers.

The paper contains numerous and ex-
tensive tables, the results of various ex-
periments made on bars of weld iron,*
ingot-iron, Bessemer steel and bronze,
and on plates of copper. In Dingler's
Journal, vol. 224, the author proved the
followiDg law to hold in the case of
Bessemer steel: — "By stretching the
metal beyond its elastic limit, the range
of the elasticity is increased not only
during the time for which the load is
applied, but also for a considerable period
of repose after the. stretching (i. e.
while the bar is unloaded) ; such period
extending to one or several days, and by
this means the elastic limit itself can be
raised to a limit greater than the load
which caused the original extension."
There can scarcely be a doubt that this
is due to the effect of what has long been
known as "secondary elastic action," and
it agrees with some results obtained by
Wohler, and published in Erbkam's
Zfitschrlft fur Buuwesen as far back as
1863. In continuing his experiments on
the subject, the author proposed to him-
self two questions : —

1. What influence the length of the
period of repose, following the extension

* This nomenclature is used as an attempt to follow
out the classification of wrought iron recently pro-
posed by Prof. Bauschinger, and to some extent
adopted in Germany.

of the bar under a given load, had upon
the magnitude of the consequent increase
of the elastic limit? and, 2. Whether any
and what alteration of the modulus of
elasticity was thereby brought about?

The testing machine used permitted of
variations in the length of the bars to be
read to the ten-thousandth of a milli-
meter; and since the parts of the bars
tested were all originally 15 centimeters
long, this corresponds to the variation of
the 1,500,000th part of the length, and
the author claims that the use of such
delicate measurements must lead to a
clearing up of the views held as to the
limit of elasticity, the definition of which
became uncertain as soon as it was known
that permanent alterations of length were
produced by relatively light loads.

Measurements with the apparatus used,
show that in materials known to be
elastic, such as wrought iron, steel, wood,
&c, Hooke's old law " ut tensio sic vis "
(i.e., the proportionality of the alteration
of length to the load which produces it),
always holds strictly within a certain
limited range. Once this range — which
the author proposes to call the limit of
proportionality — is passed, the exten-
sions become gradually greater and
greater under successive equal increments
of load. With many materials, especially

202

VAN NOSTRAND'S ENGINEERING MAGAZINE.

weld and ingot iron and the softer kinds
of steel, a second noteworthy point is
reached by a gradual increase of the load
above the limit of proportionality. The
extension is gradual under successive
equal increments of load, until this point
is reached, but then suddenly becomes
very rapid — so rapid that the image of
the scale on which the extension is
measured passes out of the field of view
of the telescope, so that a reading is no
longer possible. Under a greater load
than that corresponding to this limit, the
scale does not come back into the field of
the telescope till after a long interval, of
at least several hours, of quietude; i.e.,
the secondary elastic effort has to act for
several hours, and in some cases with
high loads for several days, in diminution
of the effect produced at. once by applica-
tion of the load. This point may be
called the " drawing-out-limit,"* and the
analogous point in case of compression
the " bulging-limit." The total effect
may be exhibited graphically thus : If
the successive loads are set off as
abscissae along any line, and correspond-
ing ordinates are drawn proportional in
length to the extensions caused by the
loads, a curve drawn through the extremi-
ties of the ordinates may be called the
stress curve. Within the limit of pro-
portionality this curve will be (at least
approximately) a straight line, but beyond
it will gradually become more and more
curved while at the "drawing-out limit" the
curve will show a more or less sharply
defined bend or angle.

The author discusses the two following
recently proposed definitions of the limit
of elasticity. One by Wertheim : the
stress under which the permanent exten- 1

sion caused by it amounts to the twenty-
thousandth part of the original length ;.
the other by Styffe : if a bar of iron or
steel is gradually stretched under a series
of loads, the first being so small as to
cause no permanent set, each acting for
the same number of minutes, and which
are so increased that each increment
is the same percentage of the whole load,
then the elastic limit is the stress under
which, acting for the prescribed time,
there is a permanent extension bearing to
the length of the bar the ratio of 0.01 of
the ratio of the increase of weight to the
whole load. Under Wertheim's defini-
tion the permissible extension in an
original length of 15 centimeters would
be 0.0075 millimeter, but the tabular
results of the experiments show that,
with ordinary materials, the limit of pro-
portionality is generally passed long
before this extension is reached, and
frequently the "drawing-out limit" also,,
when it exists. In Styffe's definition
time is made an element, which in the
author's view should not be, and he
shows by an example that the definition
may lead to a stress being taken far-
above the " limit of proportionality," and
maintains in consequence that such
arbitrary definitions are inadmissible, and
that the limit of elasticity ought to be the
" limit of proportionality," as tested for
each particular material. A consequence
of this would be that materials such as
cast iron and stone would simply haveno
elastic limit.

The time which is allowed to intervene
between successive loadings of the bar
appears to have considerable influence on
its behavior: as the following figures,
selected from the tables will show : —

A. A Bab of Weld-Ikon.

Fir-t time of testing

Second testing, immediately following first. .
Third testing, immediately following second.
Fourth testing, immediately following third . .

Kilograms per square centimeter,
(t). 00635 ton per square inch.)

Limit of
elasticity.

1,414
1,010
1,<48
1,087

Stretch
limit.

1,919
2.222

2,935
3,478

Load
removed.

2,222
2,828
3,354

Mean

modulus of

elasticity.

2,060,000
1,964,000
1,946,000
1,937,000

♦ It appears to correspond with what Prof. Kennedy has called the " breaking-down limit."

ON A NEW SYSTEM OF HYDRAULIC PROPULSION.

203

The maximum stress produced a per
manent extension of 41 millionths of the
original length.

is diminished at the second application,
but afterwards gradually increases, and
that the "drawing out limit" increases

B. A Precisely Similar Bar.

First time of testing

Second testing, eighty hours after the first. .
Third testing, sixty-eight hours after the )

second \

Fourth testing, sixty -four hours after the third.

Kilograms per square centimeter.
(0. 00635 ton per square inch.)

Limit of

elasticity.

Stretch
limit.

1,610
2.240

2,485

2,982

2,113
2,444

3,106

Load
removed.

Mean

modulus of
elasticity.

2,213

2,851

3,313
3,408

2.060,000
2,026,000

1,985,000

2,018,000

And under this maximum stress the
elongation was 18 millionths of the
original length.

From the series A it will be seen that,
when no appreciable interval occurs be-
tween the loadings, the limit of elasticity

throughout. From the series B it will
be seen that, with considerable intervals
of repose, both limits are steadily raised
throughout. This appears to hold gen-
erally.

OJST A NEW SYSTEM OF HYDRAULIC PROPULSION.

By VICE-ADMIRAL J. H. SELWYN.
From the "Journal of the Royal United Service Institution."

The subject to which I am about to
draw your attention is one of consider-
able interest, not only on account of its
connection with hydraulic propulsion,
but as leading to the study of a hitherto
neglected branch of hydrodynamics,
which may even influence, when thor-
oughly understood, some of the accepted
physical theories.

We are all more or less familiar with
the various forms in which machines for
utilizing water-power have been made.
In useful effect produced, no doubt the
turbine stands at the head of the list,
and the attempts hitherto made to apply
hydraulic propulsion to vessels have al-
most invariably comprised some form of
turbine, to which the power of the en-
gine was applied, in order to obtain a re-
active effect from water set in motion.
But in every one of these systems, not
excluding the most modern form of cen-
trifugal pump, the methods employed
were such as to produce the following
effects :

First, the water was set in motion by
discs, fans, vanes, paddles, or screws, in-
side a casing, which confined it, so as to
produce a pressure.

Next, the water under such pressure was
caused to take a determinate direction.

Lastly, a controllable ultimate direc-
tion was imparted to the water, which
might be forward, backward, or oppo-
site on the two sides, or, again, entirely
annulled by being converted into upward
pressure, at the will of the operator, and
without interfering with the movement
of the engines.

It was, in fact, the realization of a
most perfect form of propulsion, which,
being entirely based on reactive effect,
was not, and could not be, dependent,
like the paddle and screw, on the steadi-
ness of the vessel for its maximum use-
ful effect, besides presenting many other
advantages which have been often
brought to the notice of this Institution,
and which it would be out of place to.
bring forward again on this occasion.

204:

VAIN" NOSTRAND S ENGINEER IN a MAGAZINE.

But there have been also objections
made to the use of hydraulic propulsion,
and these have been invariably on the
score of lower speed obtained with a
given I.H.P., since nothing else could
have been adduced against a system
which on all other points showed so un-
mistakable a superiority. No impartial
observer will allow, if he is fully in pos-
session of the facts, that any such defect
in speed has been shown, but the objec-
tion still has great weight with large
numbers of persons, who ought to be
better informed on a matter so nearly
affecting the maritime interests of Great
Britain.

But we will, if you please, for a mo-
ment consider what the objection would
amount to, were it absolutely true.
More I.H.P., and therefore more fuel,
must be used; but this would be all, and
with more economical modes of burning
fuel and less of the "baseless supersti-
tions of the profession" (as a great
American engineering authority has
called them) as to the pressure at which
we use steam, this increase of fuel ex-
penditure might be nullified. Would
this be the case with tlie paddle and
the screw ? Clearly the question must
be answered in the negative, for both be-
ing dependent on the area of water
against which they push for their react-
ive effect, and this area being limited
constantly by the draught of water of
the vessel to which they are applied, and
occasionally by her movements in pitch-
ing and rolling, can never be equally effi-
cient with the internal reactive effect pro-
duced by a properly constructed hy-
draulic propeller. The problem involved
in the construction of such an instru-
ment is much more complex than would
at first sight appear probable, and we
shall find that one of the first conditions
of success is, that all change in the di-
rection of the water when set in motion
by the machine, which is not necessary
for our purposes, is to be sedulously
avoided. Next, that all lifting of a col-
umn of water detracts from the propul-
sive effect, since whatever power is ab-
sorbed for this purpose is taken from
that which is available for setting the
water in motion in a direction contrary
to the path of the vessel, and it is from
this source that we expect our forward
motion. Thus the water ought to be

taken into the vessel when moving with
the least possible effort, and leave it with
the least possible shock.

Theoretically, therefore, the water
should enter the bottom of the vessel by
its own gravity, should ascend an in-
clined tube forming part of the vertically
disposed propeller casing, and having
had motion imparted to it by the pro-
peller, should leave the vessel imme-
diately above water, with the velocity
and area necessary to overcome the re-
sistance of the vessel, and to give her
the desired speed. But there should be
no whirling or vortex action of the water,
and no changes of cross-sections or
bends in the tube, since all these tend to
diminish the ultimate velocity with which
the water leaves the vessel, and v being
velocity in feet per second, pressure in
pounds on the square foot is v2X-976,
but little less than the square of the ve-
locity itself.

In the " Waterwitch " I find —
Area of orifices of discharge, 6 square

feet,
Velocity of water of discharge, 30 feet

per second,
and by the foregoing formula, 878.4 lbs.
per square foot, which gives for 6 square
feet 5,268 lbs.

Now it may fairly be said that all
those hydraulic propellers we have hith-
erto seen applied, have the features,
which I have referred to as being theoret-
ically objectionable, very strongly de-
veloped. They do interrupt the motion,
they do create vortices, and they have
contractions and bends in the channels
of the water. They also develop a
pressure in the casing, due to these cir-
cumstances, which, though it may be,
nay is, indispensable in a pump or a rev-
olution indicator like Mr. Tower's, is
positively to be avoided in a propeller.

Yet, in spite of all these defects, the
hydraulic propeller has given a speed'of
vessel equal to that of the screw, under,
as nearly as possible, similar conditions.

It is also to be remarked, that it has
never yet been tried under those condi-
tions of high velocity which would be
most favorable to its action and most
fatal to that of the screw, unless we are
to admit unlimited draught of water or
a reduplication, which I should consider
most objectionable, if the effect we seek
can be got without it.

ON A NEW. SYSTEM OF HYDRAULIC PROPULSION.

205

Having thus glanced at the merits and
defects of known systems of propulsion,
I propose to bring before you the inven-
tion of Mr. George Wilson, C.E., who is
the author of papers on the "Flow of
Gaseous Substances into each other at
High Pressures," and who has, in Hol-
land, had extensive experience in the
use of Gwynne's and other centrifugal
pumps.

I said at the commencement that I
was about to refer to a neglected branch
of hydrodynamics. It is this : That
water (indeed every fluid or gaseous
body) adheres to solids with a force pro-
portioned to the square of the velocity
with which the solid passes through it.
Now, there are many familiar instances
in which this effect is seen. If a grind-
stone be driven fast in a trough filled
with water, not only is the water centrif-
ugally dispersed, but a film of water
will be seen ascending higher and grow-
ing thicker on the periphery as the speed
is increased. If a fly wheel pit be filled
with water the rim of the wheel, though
turned smooth, and more, the smoother
it is, will instantly do as the grindstone
did. If, again, a circular saw be drowned
in water, it will empty its own pit. A
ship also carries, as we know, a skin of
water with her. Neither has the prin-
ciple been left without its application
in pumps, for Messrs. Gwynne's pumps
have been most successful since the
internal wheel took the shape of a disc,
on which the blades of the former tur-
bine remain only as mere adjuncts. In
propellers, too, Mr. Aston's paddle-
wheels, which had no paddles, but only
rims, are an application of the same
principle.

But none of these are capable of per-
fectly fulfilling the conditions which
ought to be obtained for the propul-
sion of vessels with convenience and
economy, the rim paddle because of the
position and size, the centrifugal pump
because it creates a vortex, and all modi-
fications of paddles revolving in cases
because they create counter-currents
which impede instead of assisting the
motion of the water in a determinate
direction.

You will, perhaps, be surprised to hear
that a common grooved pulley, differ-
ing from the sheave of a block only in
size and shape of groove, has been found

capable of doing what is wanted with-
out any of these impediments, and that
the smoother the pulley, the better the
effect produced.

The size of pulley, or diameter, is de-
pendent upon the circumstances of the
particular vessel that has to be moved,
and the velocity with which it is sought
to move her; but it may generally be
said, that in light draught vessels a
small wheel with a high velocity will
be found most convenient, and in deep
draught vessels a large wheel with less
speed of piston ; and this suits well with
other requirements, since, while we have
been able to drive small engines at very
high speeds, it is difficult, with any re-
ciprocating system of engine, to obtain
high velocity without serious strains,,
when great weights are employed.

To give some practical idea of the
machine proposed, we will take two
types of vessel, one of light, the other
of deep draught, and show the calcu-
lation. "A" is a vessel whose draught
of water is 4 feet, her mid section 80
square feet, and her wetted surface 2,000
square feet.

The diameter of each of two pulleys,
applied on the main shaft of engine
(which is fixed transversely, and has a
speed of 300 revolutions per minute), is
4 feet 6 inches, therefore roughly the cir-
cumference is 13 feet 6 inches. This
pulley is 30 inches wide, and has in it a
parabolic groove 15 inches deep. Half
of this depth has to be deducted to ar-
rive at the mean active periphery. The
pulley will therefore be calculated as be-
ing 3 feet 3 inches in diameter, and 9.9
in circumference : 9 75x300 = 2,925 feet
per minute, about 48 feet per second.

The " Waterwitch '' attained a speed
of 9 knots or 15.21 feet per second, with
a velocity of 30 feet per second, and the
effect is known to increase as the square
of the velocity, so that if our area is suffi-
cient we ought to get with 48 feet per
second a speed of ship of about 14 knots,
unless the resistance due to form is
greater than in the "Waterwitch."
Now, let us see what area we have, and
how many pounds pressure on that area.

The area of the parabola is two-thirds
of that of an equal square. We have
here 30 inches X 15 =450, two-thirds of
which is 300 : area is therefore 300
square inches. As before vaX-976 is

.206

VAN NOSTRAND'fc ENGINEERING MAGAZINE.

pounds pressure per square foot, and
amounts to 2,247 lbs., which multiplied
by 2, the square feet in area, gives 4,494
lbs. as the pressure exerted at each pul-
ley (roughly about 2 tons). We know
that with the paddle and screw, from nu-
merous independent experiments and ex-
perimenters, the tractive force due to
100 I.H.P. is about 2 tons.

We also know that .301 of an I.H.P.
per square foot of wetted surface will
drive an ordinary ironclad 15 knots with
twin screw. Further, that 3 I.H.P. per
square foot of mid section is a fair allow-
ance for 12 knots. I might say a very full
allowance if it be effective horse-power.
With these data it becomes easy to calcu-
late what horse-power the engines should
exert to drive such a vessel at any given
speed, remembering always that with
such an instrument as this all increase
of power in the engines will constantly
be felt as increase of propulsive effort, in
the proportion of the squares of the in-
creased velocity.

We will now take the calculation for
the deep draught ship, say 22 feet
draught, with the usual proportions for a
fast vessel in other respects, but limiting
ourselves to 70 revolutions of the en-
gines, and a single engine, not two or
more, which might evidently be used if
preferred. " B," then, will have two
pulleys, or wheels, on each side, of which
the external diameter will be 20 feet, the
groove 3 feet wide, and the depth of
groove 18 inches, with 70 revolutions,
the velocity will be 59 feet per second,
and the speed of ship about 17 knots, if
there be sufficient area. The area will
be 864 square inches, and the pressure
per square foot 3,397 lbs. • X 6 =
20,382 lbs. on each of the two jets. But
20,382 lbs. is only equal to a little over
9 tons, and as with such a ship we
should employ about 3,000 I.H.P., each
hundred of which would give a pull of
2 tons, or 60 in all, it is clear that the
above area will be entirely insufficient
for our purpose. We want at least
three times as much, or six such pulleys
on each side. That is about 18 feet of
pulleys in the thickness on each side of
the engine, which would be absurd.
Now, suppose we can increase the num-
ber of revolutions of the engine* to 140
without difficulty, and I am disposed to
think this might be done, what help should

we get in that direction ? The velocity
would rise to 118 feet per second, and
1182 gives 13,924, say 6 tons per square
foot. Now we have 6 square feet in
each jet and 6 tons pressure per square
foot, so we should have 72 tons pressure
in all, or more than we require as the
result of 3,000 I.H.P. So that there is
no insuperable difficulty in the applica-
tion even in what must be regarded as
an extreme case, for if the engines were
duplex, as in twin screws, it would be
easier to attain the results, and there
would be some other advantages gained
in the event of one engine breaking
down, or where rapid turning power was
required.

It is also possible to increase the area
of groove by making the casing which
must always surround the pulleys in a
parabolic or circular form, so that the
cross-section of any part of the groove
will be parabolic in the groove and semi-

circular in the casing, and this will very
likely be found to be the most perfect
form, particularly at very high velocities,
where the water may almost be consid-
ered as a rope passing through the ves-
sel, by which she is dragged along, much
as a railway engine drags itself and its
load along a rail.

Hitherto, I have only spoken of the
pulley or wheel, but you will see by the
models ,and drawings that, there is an-
other very important feature. The water
only enters on the wheel and leaves it at
the semi-diameter, because this is the
limit of the useful motion that can be im-
parted or communicated. All beyond
the semi-diameter, whether the water be
conducted over or under the wheel,
though useful in a pump, would be dead
loss in a propeller. To meet this con-
dition there is introduced a species of
diaphragm of peculiar shape and section

ON A NEW SYSTEM OF HYDRAULIC PROPULSION.

207

lit ting nearly the lower part of the
groove, and having curved surfaces,
which form a continuation of the limits
of what has been called the " rope of
water," which form in fact with the
casing a pipe through which that rope of
water passes. It will easily be seen that
the tendency of water set in motion by
any portion of the periphery of a wheel,
and prevented from flying off centrif-
ugally, would be to follow the periphery
in its circular path, as in the helical
pump, the disc pump, and all centrifugal
pumps pure and simple. But with the
condition of propulsion to fulfil, the
energy must be directed in another path,
namely, that which is opposite to the
progress of the vessel, and in this ma-
chine it is done by, so to speak, scraping
the water off the wheel, and diverting its
motion into the needed curve. In doing
this, there must necessarily be a slight
loss of power, but it is the least possible,
consistently with the effect to be pro-
duced. The path of the water is shown
by the arrows and dotted line in No. 2
diagram. Arrangements are made by

motion by the impact of the atmosphere,
the direct pressure of which is, according
to Mr. Scott Russell :

1 lb. for wind at 20 miles per hour.
4 lbs. " 40 "

9 lbs. " 00 "

the pressure to be
of direct weight of

which the reversal or interruption of the
motion can be effected, while the engines
continue to exert their full speed ahead
something in the same way as in the
" Waterwitch."

I have now put before you the shape
of the instrument proposed and given
you some account of the way in which it
does its work theoretically. But this
latter would be incomplete, were we not
to examine the question of hydrodynam-
ics involved. In Mr. Scott Russell's
paper (vol. xxii, No. CII of the Journal
of this Institution), are some statements
^vhich show very clearly how water is
acted on by wind. Here is a case, not of
a solid body imparting motion to water
confined in a. casing, but of water set in

Query, what is
added on account
atmosphere.

He says also, that 4 lbs., or the six-
teenth part of the weight of a cubic foot
of salt water, could communicate a ve-
locity of 2 feet per second to 1 foot of
water in one second of time.

These statements will serve to show
what we might expect from such a pulley
as I have been describing, set in motion
at such a speed in a body of water.
From another paper on Tower s Revolu-
tion Indicator (vol. xxiv, No. CV), we find
that in that instrument, which is a paddle
turbine, raising water in a confined
column to a height corresponding to the
number of revolutions, the elevation of
the column is precisely that due to the
number of rotations multiplied by the
external, not the mean circumference of
the wheel, and calculated according to
the laws of falling bodies. Therefore,
even at the comparatively slow speed of
60 or 70 revolutions, we might be sure
that the whole of the water is really set
in motion, since the atoms must re-act
on each other precisely as they do when
wave motion is produced by wind, with
the remarkable difference, however, that
the motion is propagated from the motor
outwards, not from the surface inwards,
and thus in some measure resembles the
wave of translation, which delivers its
force through any distance without dimin-
ution. It is now necessary that I should
tell you what has actually been done in
practice. Engineers of high standing
had predicted utter failure. They said
that it was absurd to suppose that a
smooth pulley could communicate any
motion to water. It ought at least to be
roughened, if it did not require paddles ;
this was disproved in a bucket. Then
" it might move water in that way, but it
could never act as a pump ; " this was
disproved in a tank. Then it could, at
least, never answer as a propeller ; this
has been disproved in a boat. I have not
the least doubt that it will now pass into

208

VAN NOSTRAND'S ENGINEERING MAGAZINE.

the second phase of inventions. The
first is, " the thing is not good ; " the
second is, " the thing is not new." After
these are disposed of there will, no
doubt, come some other phases of the
subject, which are principally disguised
attempts to appropriate the profits ; and
I can only say, though I have no other
than a scientific interest in the question,
that I hope the inventor will get his re-
ward in due time, and not be left to lan-
guish like " Screw " Smith, and so many
others of our cleverest inventors. At
the beginning of this paper I spoke of
the subject being an interesting one
from purely physical points of view, and
I wish briefly to call your attention to
this part of the subject. If we admit
that the adhesion of water to a solid
moving in it is so great that the whole
velocity of the moving body can be im-
parted to it, we shall first see the import-
ance of skin friction in ships, and be
able, perhaps, to measure it more accu-
rately. We shall be able to find out the
value of the same force acting on the
surface of our screws ; we shall be led to
reconsider the whole problem of pump-
ing engines at high speeds (the account
of the work done by a centrifugal pump
at Crossness shows the necessity of this),
and generally there will be a new light

thrown on many most interesting prob-
lems in hydrodynamics.

But we may go even farther, I con-
ceive, and examine into the great forces
at work on the globe, either to retain the
water of the ocean in its place against
the centrifugal force, or to cause the
motion of great bodies of water from
east to west. What may not be due to
a speed of a quarter of a mile per second,
if with the petty speed of under 100
feet per second, such results in propul-
sion may be produced. I venture to
commend the whole subject to the
younger members of the naval profes-
sion as one full of interest for them, but
there is matter enough for thought in it
for engineers and philosophers of the
very highest caliber, and by these I hope
it will be taken up and thoroughly in-
vestigated. I believe we shall find a
law prevailing that speed of rotation
being a quarter of a mile per second, ad-
hesion is absolute. Finally, I have only
to say that when a vessel of about 130
tons now preparing is completed, I shall
be happy to give a more complete ac-
count of the advantages of this mode of
propulsion, combined with the Perkins
engines of 200 I.H.P. This I hope to
be able to do some time in the autumn
of this year.

CONCRETE SEWERS ABROAD.

From " The Builder.'

The construction of concrete drains is
increasing yearly on the Continent, not-
withstanding the competition of earthen-
ware pipes. These drains are made in
two ways. Either concrete pipes or
drain pieces are joined by concrete
mortar, or the mould of the drain is put
up on the spot, and concrete rammed
round it into the soil. Although the
latter mode of proceeding is the cheap-
est, and possesses beside the advantage
of homogeneousness and better condi-
tions of drying, the erection of the mould,
and especially obtaining an accurate
angle of fall and small gradients, offers
no slight difficulty. After removing the
mould or centering, moreover, the in-

side requires attention, if the whole is to
be finished off carefully.

These difficulties have induced Herr
J. Chailly, of Vienna, manufacturer of
concrete goods, who distinguished him-
self as a member of the Austrian com-
mittee appointed to fix a concrete stand-
ard, to construct centering for concrete
sewers by means of which the desired
form of section, and the inner surface of
the drain, may be made so exactly and
smoothly as to dispense with subsequent
finishing off. The saving thus effected
is said to be the least advantage, the
principal one being that the sewer may
be constructed with a degree of almost
mathematical exactness, which insures a

CONCRETE SEWERS ABROAD.

209

rapid draining off of fluids and prevents
accumulation injurious to health. The
apparatus recommends itself also on ac-
count of its cheapness, a length of only
6 feet being required; as soon as that
length of drain is completed, the appa- j
ratus is withdrawn, and a fresh piece be-
gun. The time taken in completing a
length is three hours, so that in a work- j
ing day of twelve hours about 25 feet
may be made. The concrete being
rammed into the soil, and thus becoming
closely connected with it, settlements
and cracks are out of the question. It
is claimed for the apparatus that, the
mould being firmly fixed, it does not j
move even during the operation of ram-
ming the concrete, while with other sys-
tems it is shaken about, and it is impos-
sible to maintain the same direction and
an exact level. After the piece of drain
is finished, the apparatus may be loos-
ened easily and without friction, and
moved forward. A number of concrete
sewers have been made with Chailly's
apparatus ; for instance, 20,000 feet run
at Linz, as well as many drains at
Vienna, Teschen, &c.

The construction of the apparatus is
as follows : — It consists of a tube, the
outer surface of which forms the inner '
surface of the drain. This tube is di- 1
vided longitudinally into six or more
parts or planks, the lateral divisions \
being of the same width throughout;
the lower or bottom plank and the
upper or vaulting piece only being
wedge-shaped. The upper wedge must
be, on the whole, narrower than the
semi-circle of the vault, so as to en- j
able the workman to detach it at the
proper time from the concrete without
pressure or loss of time. All the planks
have smooth horizontal joints, and the
tube formed of them is somewhat rounded
off inwards, or drawn together at its
front and back ends, so that its cross-
sections at those places are somewhat
smaller. This facilitates the insertion
of the tube in front in a guage ring of
the drain-mould, and behind in the com- j
pleted piece of the drain ; at the same
time it adapts the tube for making
slightly-bent drains. The lateral planks
are jointed to the gauge ring by means of
conic tenons in projections, of the same ;
the bottom plank is secured tothe gauge-
ring by two wedges. This gauge-rmg
Vol. XXVII.— No. 3—15.

cuts off the concrete to be brought in in
such a manner that each new piece of
drain is rabbeted to the piece last made.

The gauge-ring is adjusted by wedges,
and at top and bottom by squares and
plummets provided with exact marks. As
the gauge-ring must always be at a right
angle to the axis of the drain, it will,
owing to the fact that sewers have more
or less of a fall, and are, as a rule, con-
structed from below towards the top, be
not vertical, but hang over at the top.
In accordance with this, a mark corre-
sponding to the inclination is placed upon
the lower square, and the plummet set
upon it. The upper square is put upon
the correct longitudinal direction of the
drain by means of sighting rods. The
withdrawal of the apparatus after fixing
the gauge ring is effected by first loosen-
ing the bottom plank and withdrawing it,
and next securing it to the gauge-ring by
means of the wedges mentioned, while, at
the back, it is supported at the lateral
planks still in the drain also by wedges.
The lateral pieces are kept in their place
by suitable wedge stays. As soon as the
bottom plank is fixed the concrete is
stamped in between the soil and bottom
plank by means of curved pestles, and
leveled with radial joints. The lateral
planks are then drawn forward in a similar
manner, fastened, and stamped in with ce-
ment. The vaulting piece is then similarly
dealt with. The vaulting slab is fixed to a
carriage-like wheeled frame, which follows
on withdrawal. The vaulting piece settles
somewhat, but is lifted again on being
fixed to the gauge-ring. Two gauge-
rings are only necessary at the com-
mencement of work. The carriage is then
put inside the tube, and connected with
lateral pieces, for which it has supports.
These longitudinal pieces serve for fas-
tening the wedge stays, which secure the
lateral planks.

Various sections, but mostly of an egg
shape, have been made with this appa-
ratus. The sewers of Linz are construct-
ed of concrete of a thickness of 6.2 in. at
the bottom, 5.9 in. at the sides, and 5.1
in. at the crown, and they have an inner
height of 3.8 ft., and a greatest width in
the upper quarter of 1.9 feet. The con-
crete used for them consisted of one part
of Portland cement, one part of Kufstein
cement lime, four parts of sand, and four
parts of gravel. The municipality of

210

VAN nostkand's engineeking magazine.

Vienna has all the sewers of the city con-
structed after this method. The concrete
used for the bottom consists of one part
of Portland cement, three parts of sand,

and seven parts of broken stones ; that
for the lateral portions of one part of
cement lime, two parts of sand, and two
parts of broken stones.

STONE ARCHES UNDER EMBANKMENTS.

By B. S. EANDOLPH.
Written for Van Nostkand's Engineebing Magazine.

The cheapness and facility with which
iron bridges are now built seems to have
caused a very general decline in the use
of the stone arch, notwithstanding the
fact that an estimate of cost will fre-
quently show a decided difference in
favor of the latter, especially when the
span is not very great, or when high
abutments would be needed to support
an iron superstructure. Added to this,
the stone arch, when once properly
built, needs no further care to correspond
to the constant watching, painting and
repairing required by iron structures.

Such modern examples of the stone
arch as we have of less than fifty-feet
span seem to be confinecT to the semi-
circular or " full center " form. This is
very graceful and, while the crown is
near the surface so that the load can be
properly distributed, answers the pur-
pose very well ; but the frequent failures
under high embankments indicate practi-
cally that there is room for improve-
ment, a fact which will also become
theoretically apparent when an effort is
made to construct the line of pressure in
a semicircular arch so loaded.

By line or curve of pressure is meant
that line on which, if all the forces of
the load be applied in their proper posi-
tion, direction and amount, their result-
ants will maintain each other in equi-
librium. Several methods of obtaining
this are given by the authorities, as also
the demonstration of the fact that it
should lie at least one-third the depth of
the ringstone from either end, or, as
commonly expressed, "in the middle
third," so they need not be repeated
here.

The very interesting article of Mr.
Benjamin Baker on " The Actual Lateral
Pressure of Earthwork," together with
the discussion which followed in the In-
stitution of Civil Engineers, as published

in Van Nostkand's Magazine, October,
November and December, 1881, show
the futility of any calculations, in the
present state of knowledge on the sub-
ject, of the character of pressure which
is experienced by an arch under an em-
bankment. Nor is more knowledge on
the subject likely to decrease the diffi-
culty of determining the proper shape
of such an arch, since we know that cer-
tain materials give more lateral pressure
when freshly deposited than after they
have settled, while others behave differ-
ently when wet and when dry, without
regard to the length of time which they
have been deposited.

So the problem of dra\. ing an arch of
such form that the line of pressure shall
lie in the " middle third " of ringstone of
any reasonable depth becomes practically
impossible, and the way out of the diffi-
culty seems to be to control the load so
that its character shall be constant and
then proportion the arch to meet it.

In some recent designs for arches
under high embankments I have used
the following method, which seems to
accomplish the purpose, though I have
not had time to test it practically.

The abutments are carried up to a
level with or a little above the crown, as
shown in the cut, having sufficient base
to act as retaining walls, and resisting
the lateral pressure, they allow nothing
but vertical pressure to come on the
arch.

In the construction the earth is
brought up to the top of these walls,
when the lateral pressure will cause
them to move slightly inwards by virtue
of the elasticity of the material of which
they are built.

The space MNO, which has been left
open until now, is filled with thin, hard,
flat stone, loosely hand laid on their flat
surfaces. In this way the lateral press-

STONE ARCHES UNDER EMBANKMENTS.

211

ure is kept from the arch as far as pos-
sible, since the walls have moved as far
as they are likely to, and the flat stone,
while they will transmit any amount of
vertical pressure, will move on themselves
before transmitting very much lateral
pressure. If this is deemed insufficient
the space MNO could be built solid with
stone laid in mortar, and an opening a
few inches wide left on the line NO and
covered with large stone laid over the

arch ring, the true line would lie between
A and C, depending on the depth of the
crown below the surface of the embank-
ment.

This, it is scarcely safe to expect, in
view of the elasticity of the materials
composing the walls and of the tendency
of the material between the walls and
the ring to become somewhat compact
under the vertical pressure and so trans-
mit lateral pressure.

top to keep the earth from filling it up.
Supposing this arrangement of the load,
the arch is drawn almost if not wholly
for vertical pressures, depending on the
engineer's confidence in his arrangement
for securing such pressures.

In the cut are given the various forms
of the pressure lines for extreme cases in
an arch of the general form of the one
shown.

For a very high embankment, suppos-
ing the pressure to be equally distributed,
and all pressures vertical, we have the
line A. Supposing the pressure equally
distributed, but allowing pressure, in
addition to the vertical, at one half the
usual angle of repose (56-2° with the
vertical) as in the calculations for retain-
ing walls, we have the line B. Taking
all vertical pressures but proportioned in
amount to the amount of material below
the line PQ, we have the line C. Allow-
ing for pressures at the same angle as
before, but proportioned to the amount
of material below the line PQ, we have
the line D.

It will be observed that these are ex-
treme cases, so the true line for each
case must lie somewhere between them.

If we could rely on the walls to do
away with all the lateral pressure on the

The form would then approach that in
which lateral pressure was considered,
which would seem to point to the line B,
a medium between A and C as the one
most likely to meet all conditions.

The following method of drawing the
arch produces this form very nearly and
will also be found to satisfy quite a num-
ber of various conditions of load. From
the springing line as a center with the
a radius equal to the span describe a
segment upwards from the opposite
springing line to a height of 45°. Draw
the opposite side in the same manner
and connect the two arches with one of
90° tangent to the first two, the radius
of which will be .293 of the span.

This form of arch gives somewhat less
area of opening than the full center
form of the same span and height, but the
diminution is principally in the upper
part, which in large arches should not
be considered in calculating waterway,
and would make very little difference in
the passage of most vehicles. On the
other hand, in a full center arch, without
an assurance of considerable lateral press-
ure or a sufficient difference in the
amount of load at the crown and at
the haunches, the construction of a few
lines of pressure will show a very un-

212

VAN NOSTRAND'S ENGINEERING MAGAZINE.

stable condition of affairs, the line lying
far inside the curve of the voussoirs
tending to raise the haunches and let
the crown down.

This fact is borne out by the failures
of full center arches in actual practice,
which usually occur by a dropping of
the crown of the arch while at the
haunches, being unable to rise against
the load, the voussoirs are chipped and
cracked on their inner surfaces by the
excessive pressure near the inner surface
of the ring and so make room for the
descending crown.

From what has preceded it is not to
be supposed that it is intended to state
that a full center arch under a high em-
bankment will always fail, since a variety
of circumstances may, and do, obtain to
make them stable.

In embankments composed largely of
rock, gravel, or any latcose material there
is always considerable lateral pressure,
even when dry, which would cause the
line of pressure to approach the shape of
a full center arch. And beside this in
the construction of most semicircular
arches they are " loaded- " over the
haunches with stone laid in cement,
which, on setting, converts the mass into
more or less good masonry, so that the
line of pressure may lie anywhere, either
in the ring or "loading," and the struc-
ture be stable under a variety of con-
ditions for which it was not strictly de
signed.

For instance, under a given load the
shape of the curve of pressure depends
on the ratio between the rise and span,
and if we assume a segmental arch hav-
ing a rise equal to one-fourth the span,
we will find that it coincides very closely
with the curve for a load of all equal
vertical pressures. This curve might
readily be contained in the ringstone and
loading of almost any full center arch,
and if we suppose a condition of load
approximating this to occur in the em-
bankment, the curve of pressure passing
through the keystone will gradually di-
verge from the line of the ringstone and
lying above them in the loading will
reach the line of the abutment face at a
point approximately one-half the rise
above the springing line, and the arch
will in reality act as a segmental arch
with a rise equal to one-fourth tbe span,
the ringstone near the springing line

carrying nothing but their own weight.
This, of course, gives a very considerable
lateral pressure which the abutments
with such assistance as they obtain from
the material placed behind them may
be able to resist, in which case the struc-
ture will show no signs of failure, more
through accident than intention. Such
a structure, while it might carry its load
for an indefinite length of time, would
scarcely be creditable to a professional
engineer, whose aim should be not only
to accomplish his object thoroughly and
effectively, but to do it with due regard
to the amount of money expended, and
frequently to practice the strictest econ
omy, neither of which could be said to
have been considered or practiced in a
structure in which some of the parts
would never be called on for anything
but the support of their own weight.

A Monument to Alexander Lyman
Holley. — The worthy project of erecting
a monument in Central Park to the
memory of Mr. Holley is announced by
a circular issued by direction of a joint
committee, composed of special com-
mittees from the American Society of
Civil Engineers, American Institute of
Mining Engineers, and the American
Institute of Mechanical Engineers.

It is proposed that the monument con-
sist of a suitable pedestal in stone, sur-
mounted by a portrait bust in bronze.
The cost will be about ten thousand
dollars.

The sub-committee, to whom is en-
trusted the power of receiving subscrip-
tions, is composed of Chas. Macdonald,
R. W. Raymond, and J. C. Bayles. The
office of the treasurer, Mr. Macdonald,
is 52 Wall Street.

The Rensselaer Polytechnic Insti-
tute.— The plan of raising an endow-
ment fund for this institution is meeting
with encouraging success. The amount
of thirty-one thousand dollars is already
pledged.

The committee regard with much
satisfaction the fact that a warm interest
in the project is manifested by the
Alumni of the Institute, and that a
larger portion of the fund thus far
pledged is made up of moderate sums
subscribed by graduates who are actively
engaged in engineering.

THE KKSISTANCE OF VIADUCTS TO SUDDEN GUSTS 'OF WIND.

213

THE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS

OF WIND.

By JULES OAUDARD, Civil Engineer, Professor at the Academy of Lausanne.
Translated from the French hy L. F. VERN0N-HARC0URT, M.A., M. Inst. C.E.

Ix order to ascertain the condition of
stability of a structure exposed to wind,
it is necessary, in the first place, to know
the pressures which atmospheric dis-
turbances ran produce, and then to study
the effects of these forces, and the addi-
tional strength necessary to resist them.
k_\Yith regard to the first part of this
programme, it is essentially necessary to
have recourse to experience. In fact, its
only theoretical basis is a doubtful simi-
larity between a gaseous jet and a stream
of liquid, which latter, though a more
simple phenomenon, admits only of ap-
proximate investigations.

\Vhen a fluid stream, whose cross-sec-
tion is a and velocity w, strikes against a
plane surface, to which its axis is inclined
at an angle a, it spreads out in a layer
against the obstacle, as shown in Fig. 1 ;

Fig.1

&m:

and the formula which expresses the total
normal pressure on the surface is

s sin a, in which II denotes the specific
weight of the liquid, and g the accelera-

tion due to gravity. As -is double the

height which the column of water would
require to fall to attain a velocity v at
the bottom of the fall, it follows that the
dynamical pressure, in the case of verti-
cal incidence, may amount to double the
weight of the same column in a state of
rest. The pressure, moreover, is reduced
in striking against a convex surface, and
increased against a concave surface.

This phenomenon was said to be com-
paratively simple, because the liquid,
owing to its high density, is little af-
fected by the surrounding medium of air
which it displaces, or against which it

rubs. Moreover, for a stream of small
section, the surface is assumed to be
much larger than the section, in order
that the spreading out may be complete.

If now a plate having an area S, is
struck by the air, the gaseous stream will
have a cross-section, S sin a, limited
merely by the circumference of the plate ;
the central filaments will always find an
ample surface over which to spread, but
in doing this they will push out and
turn aside the other filaments ; and as
regards the outside filaments, their posi-
tion will be so far different that, with
only a very slight deflection, they will
escape before having exerted all their
dynamical force. On the other hand,
the column of air arrested by the obsta-
cle will be hemmed in by other layers of
air in motion, which it will whirl about in
forcing a sideways outlet for itself.
Lastly, the partial vacuum produced on
the sheltered face will enter as a cumula-
tive force into the problem of stability.
If these disturbing conditions could be
neglected, taking as an average II = lk
225, and <7=9.81, the formula of the fluid
stream would give, per square meter of
surface impinged on, a pressure of 0.125
v"1 sin3 a, produced by a wind having a
velocity of v meters per second, and with
an angle of incidence a.

In reality the numerical factor may
differ more or less from this theoretical
result ; but, as regards the degree of in-
fluence of the velocity and the mass of
the fluid, it appears to be confirmed by
the following considerations. An obsta-

Fig.2

cle AB (Fig. 2), being placed in the
course of a fluid, the filaments CA, CB,
diverge in curved lines, turning their

214

VAN NOSTRAND'S ENGINEERING MAGAZINE.

convex side towards the obstacle. This
curvature produces centrifugal reactions
proportional to the mass of the mole-
cules and to the square of their velocity;
and it is the sum of these reactions which
develop the "live pressure " against the
front face of the body AB. At the op-
posite side of AB, on the contrary, the
filaments AD, in tending to return to the
line of their former direction, assume
curves with the concave side turned to-
wards the obstacle. Accordingly a par-
tial vacuum, or "non-pressure," as Du-
buat terms it, is produced, which has an
effect similar to the "live pressure," and
is additional to it in the final result.

The specific weight being—, the total re-

sistance may be expressed by K II~-, or

0.0625 ~Kv2 per unit of surface, in which
the value of the coefficient K must be de-
termined by experiment. If the plate
AB is replaced by a prism more or less
elongated, the " live pressure " remains
the same, but the " non-pressure " is re-
duced, and consequently tjae value also
of K, which represents the resultant of
both forces. Thus Dubuat, who had ob-
tained K=1.43 for a plate moving in
a liquid, obtained similarly K = 1.17 for
a cube, and K=1.10 for a prism whose
length was thrice one of the sides of
its base.

Experiments made in air appear to
have given results varying between K
=1.3 and K=2.2 in the case of thin
plates ; variations due perhaps, partly,
either to the inexactness of the law of
the square of the velocity, or to the in-
fluence of the size of surfaces employed,
or to the rotatory motion of these sur-
faces in the experiments when they are
paddles of wheels.

General Morin has introduced a con-
stant into the formulae. From experi-
ments made at Brest, in 1823, by Thi-
bault, by means of a fly-wheel with lit-
tle sails on a horizontal axis, he de-
duced the formula 0.0044 + 0. 108 v2 as
expressing the resistance per square
meter. The coefficient 0.108 remains
practically constant for inclinations be-
tween 90° and 50°, provided it is re-
ferred to a square meter of surface pro-
jected on a plane perpendicular to the
direction of motion.

In 1835-37 Piobert, Morin, and Di-
dion, made observations on the fall of
a plate suspended to a cord; the laws
of the motion being indicated, with re-
spect to the guide pulley, by a clock-
work apparatus. The resulting formula,
namely, 0.036 + 0.084v2 + 0.164/, contains
a term proportionate to the accelera-
tion j in the case of variable motion,
which vanishes for uniform motion-
Analogous formula have been obtained
for parachutes. The velocities observed
did not exceed 10 meters (33 feet) per
second.

Whereas for slow motion the law of
pressure appears to be best expressed
by formulae having two terms, of which
one is proportional to the square of the
velocity, and the other is taken as a
constant by some, or proportional to
the simple velocity by others; it is
found, on the contrary, that the in-
tensified phenomena of ballistics indi-
cate a greater variation than the square
of the velocity. Piobert estimates the
resistance to motion of a projectile
whose section is s as 0.023 sv'1 (1 +
0.0023u); but sometimes it is expressed
by a single term proportionate to v*.
As regards the reduction of pressure due
to the obliquity of the current, experi-
ments indicate a less rapidly diminish-
ing factor than the square of the sine.
Didion found that in bending the oppos-
ing surface so as to form a convex two-
sided angle, and inclining each of the
two faces thus formed at the same an-
gle a to the direction of motion, the
formula has simply to be multiplied by

a
— 3, so long as a is between 90° and 65°.
90

Hutton had arrived at the complicated
formula 0.135 s11 o* (sin a) 1M cos a for
the total pressure upon the surface s of
a plate in the case of velocities below \0
meters (33 feet). It will be noticed in
this formula that the pressure per unit
of surface is considered to be proper-
tional to — or to Vs, which agrees with

Borda's experiments, which indicated a
pressure of 0.09 u2 per unit of surface, on
a square whose side was 0.11 meter (4f
inches), and 0.105 v2 when the side
amounted to 0.25 meter (9J inches).
The influence of the size of the area on
the result is explained by the fact that

THE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS OF WIND.

216

the filaments of the current near the sides
only produce a partial effect, and the
larger the surface, the smaller is the pro-
portion of the perimeter to the area.
However, Didion, Thibault, and other
observers, have, on the contrary, arrived
at the conclusion that the total pressure
is proportional to the surface, and inde-
pendent of its form. Morin gave as an
objection to Borda's experiments, made
with a fly-wheel having small sails turn-
ing a vertical axis, that the effect of the
friction of the apparatus had not been
calculated.

The resistances offered by the air to
railway carnages in motion have been
variously estimated : Thus Harding
gives 0.0627 v\ and Ruehlmann 0.117 v*
per square meter of front section. The
circumstances, however, are complex, and
when it is desired to estimate the resist-
ances as closely as possible, it is neces-
sary to go into the details of the car-
riages in order to ascertain the effect of
the air in the spaces between them.

It is generally accepted as an axiom
that the resistance offered by air at rest
to a moving body is equal to the press-
ure which wind moving with the same
velocity would exert on the body at rest.
Smeaton, adopting a table drawn up by
Rouse for winds having velocities not
exceeding 72 feet per second, appears to
have accepted pressures denoted by the
formula 0.0023 v", which are given in
a tabular form in the Minutes of Pro-

ceedings, vol. v., p. 292. In the same
volume (p. 29(>) will be found the results
of the careful experiments made by
Colonel Beaufoy in 1815, with plates
however only 1 foot square, which may
account for these pressures being less
than those adopted by Smeaton. Gen-
eral Morin deduced a formula from some
experiments by Thibault in 1826, which
gives results approximate to those of
Smeaton, but decidedly greater than the
resistances experienced in moving flat
discs in still air, which would support
Dubuat's opinion as to the incorrectness
of the axiom mentioned above.

It would appear from calculation that
the pressure on a cylinder is two-thirds,
and that on a sphere half of the press-
ure on their diametral sections. Borda,
however, obtained by experiment the
smaller values 0.57 and 0.41 as the rela-
tions of these pressures. For a prism
presenting a right-angled isosceles tri-
angle to the air, he obtained the propor-
tion 0.73, and for a cone the values 0.69
or 0.54, according as the angle at the
apex was 90° or 60°.

The velocity of the wind is recorded
by anemometers. Thibault obtained the
pressures by plates attached to springs
for measuring the resistance.* In a
similar manner Mr. Paris took measure-
ments of the wind at sea by fastening
small boards to a deal rod which served
as the spring, and he obtained the follow-
ing results :

FEET PER SECOND.

Velocity of the wiDd

2.6! 5.911.219.730.243.059.7

.408.8 125.31 150 0

LBS. PER SQUARE FOOT.

Pressure exerted

1 1
0.02 0.0! 0.872.13 4 25J8. OS

12.. ^n

22.12 37.90 51 20

1 1 i 1

These figures approximate to those
given by Smeaton' s formula, and are
smaller than those derived from Hut-
ton's formula, which formulae would give
for a great storm of 151 feet velocity per
second about 51.8 lbs. and 57.3 lbs. per
square foot respectively. In the higher
regions of the atmosphere the velocities
may be very great, as it is stated that, in

1823, Green traveled in a balloon at the
rate of 210 feet per second.

The absolute relation between the
pressure and the velocity is by no means

* Dr. Lind, in 1775, employed a reversed siphon con-
taining water; and the wind entering one branch
made the water rise in the other branch, thus afford-
ing a measure of the pressure exerted. ( Vide Minutes
of Proceedings Inst C.E., vol. v., p. 290, and Philo-
sophical Transactions, 1775, p. 353.— L, F. V.-U).

216

van nostrand's engineeking magazine.

indispensable for ascertaining the sta-
bility of structures exposed to the wind.
It is sufficient for this purpose to find
the greatest pressure that may occur in
a given locality during a sudden squall.

Rankine states about 55 lbs. on the
square foot as the greatest wind-press-
ure observed in England by anemometers
or dynamometers, which is confirmed
by the fall of chimneys and other build-
ings. However, a pressure of 61 lbs. on
the square foot was recorded at Liver-
pool during the storm of the 7th of Feb-
ruary, 1868, and of 71 lbs. on the 27th of
September, 1875.

The violent storm of 1876, which over-
turned several chimneys in Germany,
was reckoned to have a velocity of 102
feet, and a direct pressure of 29.5 lbs.;
but, taking into account the " non-press-
ure," due to suction at the back face, it
is estimated that the total resultant
pressure on these structures must have
been a third more, and consequently
equal to 39.3 lbs. per square foot.

The upsetting of a train between Nar-
bonne and Perpignan, in December,
1867, indicated a pressure of between 30
lbs. and 50 lbs.; and other* similar acci-
dents with empty wagons on the same
railway in February, 1860, and January,
1863, indicated a pressure of from 25 lbs.
to 33 lbs. No other part of France is
exposed to such violent storms ; never-
theless, in considering the stability of
light-houses, Fresnel allowed for the
possibility of wind-pressures up to 56
lbs.

It would appear that American engi-
neers, for the resistance of bridges, as-
sume wind-pressures of 30 lbs. per
square foot upon the loaded and 50 lbs.
upon the unloaded structure, although
certain local tornadoes in that country
might have exerted forces amounting to
as much as 84 and even 93 lbs.*

Instead of waiting for chance acci-
dents, which have to be investigated
after the event with inadequate data, it
would be advisable to set up apparatus
at once in certain meteorological ob-
servatories for registering the pressure
of great gales. For example, a kind of-
case of pigeon-holes might be placed in
windows facing in a suitable direction,
these holf s being closed by a series of

♦Minutes of Proceedings Inst. C.E., vol. lxiv., p.
352, and vol. lxvi., p. 388.

little shutters one above the other, capa-
ble of moving inwards under certain
pressures of wind, being guided by lit-
tle rollers, and made to close again
against the external rabbets of their re-
spective frames by springs or counter-
poises with suitably gradauted power.
Lastly, each of these movable panels
might be so arranged that the moment
it began to open it should unhook a
signal which would bear evidence to the
movement even after it had closed again.
It would suffice after each storm to as-
certain, by a rapid inspection, which of
the panels had yielded to the wind, and
then whichever of these panels offered
the greatest resistance would measure
the pressure experienced.

Of all engineering structures, suspen-
sion bridges are the most easily acted
upon by wind. Their primitive methods
of construction were defective through
excessive flexibility. The accident which
happened to the Roche-Bernard bridge
on the Vilaine, on the 26th of Octo-
ber, 1852, and the successive injuries to
the Menai bridge in 1826, 1836, and
1839, may be cited as examples. The
chains of the latter bridge, though
clashing together violently, bore the
strain ; but a number of transverse pieces
and suspension rods broke, and 160 feet
of flooring hung in the air in 1839.
According to the bridge-keeper, the
undulations of the roadway attained an
amplitude of 13 or 16 feet, and the
greatest deflections were observed at
the distance of a quarter of the span
from the piers. It is evident that every-
thing gives way in these irregular un-
dulations, which are different for the
chains and the roadway. The Menai
bridge was strengthened by various
means. The Roche-Bernard bridge was
provided with a counter cable, curving
upwards and placed under the roadway ;
and notable progress has been achieved'
in the design of more recent works. The
Americans, in developing the principle of
the stiffening girder, have also added a
series of straight and sloping cables com-
ing from the top of the piers and sup-
porting various parts of the roadway.
They have, moreover, in some large
bridges, anchored the roadway to the
rocks by stays underneath, a method
which is not free from objections any
more than the parabolic counter cable

THE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS OF WIND. 217

of the Koche-Bernard bridge, for the
variations in temperature may at one
time loosen and at another time stretch
these understays.

In the Ordisli system, as applied to
the Albert bridge, Chelsea, the upper
stays, starting from the tops of the piers
and ending at various parts of the road-
way, are connected with the vertical sus-
pension rods at divers points of cross-
ing, which increases the total rigidity.
Sometimes, as at the Lambeth bridge,
rigidity is obtained by the introduction
of cross bracing or diagonal bars be-
tween the suspension rods ; or, as at
Pittsburg, the chain itself is made rigid,
assuming the appearance of two sloping
lattice girders of variable height, and
attached to their narrow extremities, at
one end to each other in the center of
the span, and at the other end to the
tops of the piers.

The great transversal inclination in
certain bridges to the two funicular
planes, by which the cables, spreading
out at the tops of the piers, come to-
gether in the center of the span, affords
a powerful resistance to lateral oscilla-
tions.

"With these improvements the suspen-
sion system, without losing its inherent
lightness, is protected from irregular
undulations when exposed to wind ; so
that the wind pressure merely acts on it,
like on any other structure, in producing
an increased molecular strain which has
to be provided for by strengthening the
parts liable to be affected.

It is true that a great number of sus-
pension bridges exist which were con-
structed on the old flexible principle,
and have stood for many years ; but
their preservation is doubtless due, in
most cases, to their not having experi-
enced the full force of the wind whirl
ing under their roadways, owing to their
small height above the water, or other
circumstances. The most exposed
bridges are those which traverse deep
and shut-in gorges at a great height.

Wind has no effect on massive stone
bridges ; but every light bridge, whether
of iron or wood, although rendered
rigid, is liable to side strains, or small
elastic vibrations producing molecular
deformations, upon which the conditions
of resistance of the material depend.

Though the motion of wrind is gener-
ally parallel to the ground, its action on
the underside of the roadway may be-
come considerable, owing to the rebound
of the wind from the bottom of ravines,
which occasions the great danger to light
flexible suspension bridges of being raised
and falling again violently. When the
wind, blowing in sudden gusts, lifts the
platform slightly, the platform falls again
for a moment below its normal level to a
similar extent, so that the pressure of
the wind from below produces eventually
the same strain as if its action was
added to the load. Accordingly, in
special cases, where it might be possible
to estimate at an appreciable amount the
vertical resultant of a storm beating
against the roadway of a bridge, it would
be correct to treat it as an extra load on
the bridge.

The effect might be still more serious
in a bridge with several continuous
spans, for, as nothing could ensure the
concordance of the oscillations of the
various spans, it would be necessary to
provide against the worst case of a
pressure from above on certain spans
aggravated by a pressure from below on
certain other spans.

Putting aside, however, these acces-
sory or derived effects, let the wind be
considered solely in its horizontal direc-

| tion, in which it displays its greatest
power, and, knowing its force on a single
solid surface, let an endeavor be made to
calculate the force exerted on several

; open, or partly open, surfaces.

Taking the case of a bridge consisting

I of two solid girders, though these gird-

! ers cover each other completely in a
geometrical sense, yet the first, wrhilst

i exposed to the full force of the wind,
does not completely shelter the other.
Thibault experimented on two square
screens covering each other, and placed
at a distance apart equal to the length
of one of their sides, and found that the
wind pressure on the one screen being 1, a
total wind pressure was experienced on
the two of 1.7 In the case of a bridge,
the wind pressure cannot be so high, as
instead of four edges there are only two
at the most (when the platform is half-
way up the girders), round which the
wind can whirl and beat against the
second surface ; the coefficient of in-

218

VAN NOSTRAND'S ENGINEERING MAGAZINE.

crease in such a case, deducted from
tlte preceding instance, will perhaps
amount at most to 1.4. It would be re-
duced to 1, and even less, if the girders
were connected by solid platforms at the
upper and lower edges. Lastly, in the
case of a single platform, placed at the
top or the bottom, it would be perhaps
necessary to estimate the total lateral
pressure as equal to 1.2 time that which
the side directly exposed would experi-
ence. It is evident that if a train is on
the bridge at the time when the storm is
raging, the resistance that it offers to the
wind aggravates the strains on the struc-
ture.

Considering, now, the case of trellis
girders, each opening may be regarded
as an orifice, with thin sides, through
which a jet of air rushes ; there will be
some contraction of the fluid vein, and
the side will experience a little greater
resistance than the ratio between solid
and void would indicate. If p denotes
the wind pressure, s the whole surface of
the side of the girder, 6 the open portion
of this surface, and k the coefficient of
contraction, the pressure on the girder
will be p{s—Jc6). The value of k, ac-
cording to D'Aubuisson, would equal
0.65 for small orifices, but as it doubt-
less varies inversely as the ratio of the
perimeter to the surface, which dimin-
ishes as the dimensions increase, it may
be assumed that k approaches unity in
the case of large openings. However,
as its real value is not known, it will be
better to risk exaggerating it in the case
under consideration.

Suppose, now, that a second side ex-
actly similar is placed behind the first, it
receives the shock of the portion of wind
which has passed through. This wind
may be considered to have been made
homogeneous by the whirling which oc-
curs in the interval between the two
girders, and to have a reduced force

k(j
p — , according to the relation between

the amount of air which has traversed
the first girder and the total original
mass. Consequently the second trellis

will experience a pressure — — (s—ka) ;

and similarly the wind which passes
through it will have its force reduced to

/Jeff

p[—y. If there are n successive gird-
ers, the sum of the pressures experienced
will be "

Is— k(j\

' ka &V2
1 + — +

. . +

fcn-l an-\

= p-

n-i )

sn _Jcn Gn

r,n— 1

As the above calculation does not take
into account the wind which may come
round the sides of the front girder, a
certain coefficient must be introduced,
smaller than in the case of solid girders,
as some opposition is offered to the in-
flowing wind by the wind passing through
the girder. Perhaps the coefficient 1.10
would amply suffice in the majority of
cases.

Another process of approximate calcu-
lation of the pressure of wind on a trellis
girder has been employed by Mr. Nord-
ling. He assumes that the filaments of
air slant a little, s® that those which
pass through the openings of the first
girder strike against the solid portions
of the second. In this way a succession
of trellises would finally act as a solid
girder, when no openings are visible in a
direction only slightly deviating from
the normal.

Having ascertained the lateral force
exerted by the wind against the roadway
of a bridge, it is necessary to calculate
the special molecular strain which it
tends to set up, in order to add it to that
produced by the permanent and moving
loads. In resisting the wind, the road-
way acts as an imaginary girder whose
flanges are the actual girders of the
bridge, and whose lattices are the hori-
zontal braces and wind ties. The re-
sistance, moreover, offered by the irregu-
lar interlacing motion of the trains must
be taken into consideration. Owing also
to the wind coming in gusts, thus caus-
ing a reaction, its effect on each girder,
whether tensive or compressive, must be
considered as added to the strain due to
the load, and in the case of several spans
the most unfavorable condition must be
allowed for.

An arch has the advantage over a
straight girder of opposing less surface

THE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS OF WIND. 219

to the wind in the central portion, whilst
the opposite is the ease with a bow-
string.

Two examples of iron arches, with nar-
row roadways, spanning very large open-
ings, are those of Oporto, on the Douro,
which has a width oi 14 feet 9 inches be-
tween the parapets and a span of 525
feet, and that of the Montereale, on the
Cellina torrent, which has a width of 9
feet 10 inches and a span of 272 feet. But
these bridges are secured against the
wind by special contrivances ; the first,
by giving a batter of 0.1164 to each face
of the bridge, so that the distance from
center to center of the arched ribs, which
is only 12 feet 10 inches at the crown, is
increased to 49 feet % | inches at the
springings ; the second by an external
wind bracing, namely, by side buttresses
coming from the haunches of the arch,
and butting against the masonry at two
points 27 feet 7 inches apart, whereas
the distance between the arched ribs is
only 9 feet 10 inches.

Certain structures may be liable to be
wholly overturned by a gust of wind.
Iron superstructures are generally free
from this danger in consequence of their
weight, except perhaps during a danger-
ous stage in some methods of putting
them in place, especially if detached
girders are being moved. On the con-
trary, the iron piers of very high viaducts
need to be very firmly anchored in their
masonry pedestals, as Mr. Nordling has
pointed out in his memoir about various
works on the branch lines of the Orleans
Company. These kinds of piers are
eventually strained as elastic braced
structures fastened at their base and sub-
jected at their summit to violent hori-
zontal thrusts. On this account, instead
of distributing their mass in a number of
external and internal uprights, it is better
to concentrate it at the angles in only
four ribs connected together by cross-
bracings. The anchorage at the base is
rendered more economical, or more power-
ful, by fastening buttresses to the piers
near their foot so as to enlarge their base.
If the height does not exceed 130 feet, as
for instance at the Bellon viaduct, the
uprights may be curved outwards towards
their base, so as to spread out without
the aid of special stays. It would be
equally feasible to secure the tops of high
piers by stays fastened near the top of

the piers and firmly anchored to the
ground ; but the system of buttresses is
more aesthetic, and is not liable to get
loose. One of the high piers of the
Bouble viaduct, Fig. 3, will serve as an
example to illustrate, by an approximate
process, to what severe strains such a
structure might occasionally be exposed.
Mr. Nordling has assumed the wind
pressure at 55.3 lbs. per square foot,
without allowing for a train on the
bridge, as, in his opinion, if such a

lClyJ. r —

Pier of the Bouble Viaduct.

storm ever burst upon these structusre
the traffic would be suspended for a time ;
and, moreover, the above pressure ap-
pears to him excessive for the locality.
Let, however, the worst possible case be
considered by imagining a concurrence of
adverse circumstances, the structure being
in a very exposed situation, and the full
fury of the gale suddenly occurring whilst
a train is passing over.

Taking only a half pier containing two
uprights and the intermediate bracing,
the span being 164 feet, crossed by two
lattice girders 14 feet 9 inches high,

220

van nostrand's engineering magazine.

it appears that, allowing for the
spaces, the wind, having a pressure of
55.3 lbs., would exert a total stress of
about 20 tons at a height of 196.2 feet
above the footings, which gives a moment
of 3,924. The pressure on the train is
16.2 tons, with a leverage of 210.3 feet,
giving a moment of 3,407. Lastly, the
moment of the pressure of the wind on
the half pier amounts to 20 tons X 92.85
feet =1,857. Thus the total moment of
overturning on the edge of the base is
9,188. The moment of stability due to
the loads is obtained as follows : taking
60 tons as the weight of the half span,
and 120 tons as the weight of the half
pier (the cast iron cylinders being bal-
lasted with concrete), and allowing 42.5
tons as the weight of the train which
suffices to prevent its being overturned
by the gale, the total weight amounts to
22 2 £ tons, and the half width of the base
being 33.8 feet, the moment is 7,520,
leaving a deficiency of 1,668. To pro-
vide for this the anchorage tie must

1,668

exert a tension of

67.6

= 24.69 tons.

Without the help of the buttresses the
width of the base of the pier would be
only 24 feet 3 inches, instead of 67 feet 7
inches, and the anchorage would be sub-
jected to the great strain of 267 tons.

In order to form a notion, not merely
of the strain on the anchorage, but of the
strain on the whole structure of the half
pier, a graphic illustration is given of the
polygon of forces, considering, for the
sake of simplicity, the imaginary case of
an articulated structure. The lattice,
moreover, is hypothetically reduced to
the lines of Fig. 4, by omitting as well
the foot of the straight uprights, replaced
by the corresponding curved or polyg-
onal stay, as in each row of bracing, that
of the two diagonals which, exposed to
a wind from the left, would be strained
in compression, and are considered to be
too flexible to offer an effectual resistance
in this way.

The external forces applied to the
various summits produce the following
horizontal components. At the summit
A the whole force of the wind against the
beams and the train is brought to bear,
namely, a force of 40.04 tons obtained by
dividing the moment, 7,331, by the
height, 183 feet, of the point A above the
base. The pressure against the half pier

amounts to about 2 tons acting at each
of the points B, G, H, . . . I, situated
on the side which the wind strikes. The
weights or vertical components are: —

Bars under compression.
" ." tension.

5JJT5-

Scale
Theoretical Structure of the Pier.

51.25 tons at A, due to the loaded road-
way ; the same weight at B increased by
a portion of the pier, amounting al-
together to 57.25 tons ; lastly, in each of

LAA1&

THE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS OF WIND. 22 1

the points G, H, . . . I and C, D, . . .

E, a vertical force of 0 tons. The re-
actions in equilibrium developed by the
base of support arc : at K. the tension of
anchorage, amounting to 24. 69 tons as

in projection all the wind pressures, is
equal to 00.04 tons.

The resultants at the different points
consequently assume oblique or vertical
directions. The oblique resultants are :

Fig.5

eta

calculated above, acting from the top to
the bottom : in F, a vertical upward re-
action equal to the total weight increased
by the strain of anchorage, namely, to
247.2 tons. ; and a horizontal force acting
from right to left, which, counteracting

65.04 tons at A ; 6.3 tons at each of the
points G, H. . . . I of the left up-
right ; and 254.4 tons at the point F of
the right upright. The state of equilib-
rium of the external forces is shown by
a closed polygon in Fig. 5. Moreover,

222

van nostrand's engineering magazine.

this figure is completed by the addition
or grouping of a series of other closed
polygons representing the respective
states of equilibrium of the various sum-
mits of the articulated system of Fig. 4,
under the influence of the internal and
external forces acting on each of them.
The inscription of identical numbers in
Figs. 4 and 5, serves to indicate their
connection ; thus, for example, the closed
polygon 8, 9, 11, 12, 6.3 tons in Fig. 5
proves that the point H of Fig. 4 is in
equilibrium under the external force 6.3
tons, the tensional strains of the bars
Nos. 8, 9, 12, and the compression of the
bar No. 11, the intensities of the forces
being measured by the size of the lines on
the diagram, Fig. 5. It will be observed
that the left side is in tension from G to
K, the greatest tensional strain, of about
190 tons, occurring on the portion No.
34. With a cast-iron pipe having an ex-
ternal diameter of 1 foot 8 inches, and an
internal diameter of 1 foot 4 inches, this
strain would amount to 1.9 ton per square
inch ; but, as previously stated, the
Bouble viaduct was constructed on the
supposition of the maximum pressure
being less. The compressive strain
reaches 422 tons at the portion No. 40,
which would amount to 4.1 tons per
square inch, but in reality the strain is
less if the uprights are made complete,
as shown in Fig. 3.

Moreover, it is certain that the rigidity
of the cast-iron columns and their bolted
flange- joints must considerably modify
the conditions of the problem. Instead,
therefore, of merely comparing the pier
to an articulated system, each member of
which is considered to be free to deflect
in any way, as assumed above, it would
be necessary, in a complete design, to
study the transmission of force resulting
from impeded deflections.

In certain mechanical structures, as,
for instance, in swing bridges with short
tail ends, the action of high winds may
stop or impede their motion without
actually producing any dangerous amount
of damage.

High timber stagings, owing to their
lightness and the broad surface presented
by their planks, are exposed to considerable
risks of damage by wind. An excellent
method for strengthening them was
adopted at the Chaumont viaduct, which
is 164 feet high, and has three tiers of

arches, each of which was provided with
a temporary platform for the supply of
materials. The staging was braced in
various directions by iron wire cables,
very tightly stretched and firmly an-
chored.

When a structure rests without suf-
ficient adherence on a fixed base, a
lateral thrust would turn it over by de-
taching it from its support ; but if its
fall cannot be effected without some in-
determinate or chance cleavage, the rup-
ture will take place in an oblique and
downward direction B A, Fig. 6, because

a certain triangular prism, BAC, pos-
sesses a stable position, on account of the
leverage of the weight being great, and
that of the impact of the wind small, in
relation to the axis of rotation.

In reality, so long as the solid is not
broken, the pivoting does not tend to
take place on the extreme edge A, but
upon some neutral axis of the section of
rupture AB ; as in every prismatic body,
subjected to a bending strain, fracture re-
sults from the crushing of some por-
tions and the tearing of others.

The direction AB being defined by the
indeterminate CB=£C, the external forces
acting are, the weight of the prism
ABEF, and the pressure of the wind on
BE. In calculating the combined effects
of pressure and flexure exerted on AB,
the chance of fracture would be investi-
gated from the position of the critical
point A or B. The first of these points .
is the place of maximum compression ;
assuming that it reaches the limit of im-
minent crushing, an equation of ultimate
resistance could be formed containing x
and the pressure p of the wind per unit
of surface as the variables. Then, by
finding what value of x in this equation
would make p a minimum, the direction
of rupture would be obtained, provided
that it is the point A where the disinte-
gration begins. Such would be the con-

HIE RESISTANCE OF VIADUCTS TO SUDDEN GUSTS OF WIND. 223

condition of a building very much strained
by its own weight before the intervention
of the wind.

Under other circumstances, however,
the point B might eventually be subject
to a tension liable to prove more danger-
ous, though smaller in amount than the

at A,

to the material

pressure

being less able to bear tension than com
pression. It would be necessary, there-
fore, to examine the equation of rupture
with regard to the point B, which might
lead to another value of x applicable to
the case where the disintegration com-
menced at this edge.

Nevertheless, nothing indicates that
the fracture must be a plane surface. It
might possibly slope somewhat in a homo-
geneous body ; and in a masonry struc-
ture the fracture would run along the
joists in some zigzag line; and these con-
siderations limit the value of theoretical
investigations.

Another reason for avoiding putting
down the equations is, that they wrould
lead to the disputed question of ultimate
resistance in the complicated case of a
material opposing an unequal resistance
to tension and compression. With refer-
ence to the practical and legitimate need
of a method or formula of safety applic-
able to the case in question, it is allow-
able to start on the simplifying hypoth-
esis, commonly admitted in investigations
of the stability of masonry, of the ab-
sence of cohesion, or neglect of the re-
sistance to tension. If the line AB, what-
ever its direction, is regarded as a pre-
existing fissure, the initial effect of the
gust of wind, instead of being a pivoting
on some neutral axis, would be from the
first a rotation on the point A itself, at
least, if the slight crushing of the edge is
neglected. If, for example, Fig. 6 repre-
sents a wall with a rectangular base, the
equation of actual equilibrium of rotation

. h2-x"

=IIa5

3A-2z
~6~

where II is the

weight of a cubic foot of masonry. To re-
main stable against a given wind pressure p,
the wall must have a thickness a sufficient
for the most dangerous value of x. Now
the value of x, which makes a a maxi-
mum in the above equation, is given by
or x = 0.382//.: and the

i/P?

'ph
II*

If, for instance, />= 55. 3 lbs. per

square foot, and 11 = 150 lbs. per cubic
foot, the proper thickness would be a =

0.65 \/h, where a and // are in feet.
With this value there would remain the
cohesion, which has been neglected as a
factor of safety ; and there would be no
fear of the occurrence of extensions or
of fissures, since, even with pre-existing
fissures, the wall would not stir. If, how-
ever, a greater degree of stability was
requisite, it would suffice to increase a by
an optional amount.

An interesting instance of oblique rup-
ture, caused, not by the wind, but by a
stroke of the sea, occurred on the 8th of
January, 1867, to the masonry tower
beacon of "Petit Charpentier" at the
mouth of the Loire. From an investiga-
tion of this accident, Mr. Leferme arrived
at the conclusion that the pressure ex-
erted by the blow of the wave must have
amounted to about 6,140 lbs. per square
foot. Mr. Thomas Stevenson, M. Just.
C.E., deduced some equally high press-
ures from observations at the Skerry-
vore rocks, which appear to be confirmed
by the jets of water sometimes dashed to
a height of 100 feet against lighthouse
towers. Nevertheless, in most storms,
and in most sea-coasts, the dynamical
pressures exerted by the shock of the
waves are generally estimated not to ex-
ceed from 600 1,000 lbs. per square foot.
Even with this reduced value it is ques-
tionable whether, in the case of light-
houses and other structures in the sea, the
wind pressure is not less dangerous than
the shock of the Avaves. Taking the
latter at 1,024 lbs., and the wind pressure
at 55.3 lbs. per square foot, and assum-

Fig.7

~JJm

....

ing a tower to be immersed 13 feet (4
meters) in the water (Fig. 7), to what
corresponding thickness is a = 1.0705 | height would the tower have to be raised

224

van nostkand's engineeelstg magazine.

for it to be in as much danger of being
overturned by the wind as by the waves ?
The sea in a storm would perhaps rise 8.2
feet (2.5 meters) above its ordinary level ;
and if the smaller pressure on the bottom
5 feet (1.5 meter) is neglected, the total
pressure on a height of 16.4 feet (5
meters) would amount to 16,794 lbs.
With a leverage of 13.12 feet (4 meters)
the over- turning moment with respect to
the base is 220,000. Now, supposing the
height of the tower to be x, the portion
out of water will be exposed to a wind
pressure of 55.3 lbs. (x— 13), and the
moment of this force, 27.65 (ic2 — 169),
will only become equal to the former mo-
ment when x reaches the height of 90 J feet.
If the same calculation is repeated on
the assumption that the shock of the sea

has its greatest possible degree of in-
tensity, namely, that the wave rises 13.12
feet above its ordinary level, and exerts a
pressure at the same instant of 6,144 lbs.
on the whole height of 26^ feet, the cor-
responding moment of 2,116,000 could
not be equaled by the wind pressure on
a tower less than 277 feet.

On the contrary, in the case of a
viaduct only opposing a resistance to the
water at the lower extremities of its
piers, whilst the wind beats upon the
lofty superstructure as well as against
the piers, there is in all probability
more danger to be apprehended from
the wind. As to the conditions under
which the Tay bridge catastrophe oc-
curred, the author is not in a position to
discuss them.

THE WATER-METER SYSTEM AJSTD WATER METERS.

By MR. JOHN COLEMAN.
Abstract of a Paper read before the Society of Arts.

Steam engines now pump millions of
gallons of water through vast pipes, often
spanning wide rivers, or rising over hills
and sinking into vales, enabling water to
be conducted under immense pressure.
Gigantic reservoirs now exist, containing
many days' supply, and aqueducts of stu-
pendous proportions cross rivers at a cost
of millions. In the streets of cities mil-
lions more have been expended for the
great distributing pipes, until, to supply
water for the necessities of life, the cost
amounts to sums which seems almost
fabulous.

Notwithstanding all this expenditure,
gallons are run off to obtain a single glass
of water, pipes are left open in sinks and
closets, while few reflect that every gal-
lon brought into a city and forced to high
buildings is sent there at the expense of
the taxpayer.

They do not comprehend that if five
gallons of water are wasted for the one
gallon really needed by all consumers the
public works and the water taxes must be
five times as large as is necessary. It is
directly proved by the experience of Lon-
don and Providence that about thirty
gallons per day per human being is am-
ple to supply all real needs ; but in con-
sequence of the system generally adopted

by American water corporations, which
put a price per year to consumers and
allow them to draw all the water they
choose, the quantity per person has stead-
ily risen until it has reached, in some
cities, the incredible quantity of 150 gal-
lons per day.

Time after time, in many cities, the
public works have been doubled to cope
with this increasing demand, but their
limits have soon been reached, until water
commissioners, in despair, have now se-
riously sounded the alarm. The public
conscience has been appealed to, detect-
ives and police have been sent from
house to house in Chicago and other
places, and fines and penalties have been
inflicted to stop this waste, but all to no
purpose. Every water report puts the
waste at, at least, sixty per cent.

The twenty-sixth annual report of the
Board of Water Commissioners of the
city of Hartford, in which it states
that the average daily amount of water
used and wasted in Hartford is equiva-
lent to over one hundred gallons to each
and every person — a quantity which no-
city in Europe approaches, and which is
only equaled by two or three in our own
country ; that the cause of this waste was
permitting the water to run in cold

THE WATER-METER SYSTEM AND WATER METERS.

225

weather to keep the pipes from freezing ;
in summer, letting the water run to cool
it ; from extravagant use of hose and
lawn sprinklers during the hours pro-
hibited by the rales, and at all times
from water closets.

The report states that it is imprac-
ticable to use water meters until one is
invented which combines cheapness and
a fair percentage of accuracy and dura-
bility. The same report shows the result
of an investigation of this waste in the
case of the average dwelling-house in St.
Louis, occupied by a family of six per-
sons. The amount of water was meas-
ured, when used in the ordinary way, and
found to vary from 1,310 to 1,903 gal-
lons per day. The amount consumed
was then measured, when care was taken
that there should be no waste in the
closet, and found to be 758 gallons per
day. Subsequently the water was meas-
ured, when, as stated by a member of
the family, a very free use of water was
made, only ordinary care being taken to
prevent its wasting, and the amount con-
sumed was found to vary from 433 to
464 gallons per day. On the other hand,
one day an account was kept of the
amount actually consumed for useful pur-
poses, and it was 178 gallons.

The evil of enormous waste is not one
of mere dollars and cents, for water works
are depended upon against great con-
flagrations. But, with the present dis-
tributive pipes in the streets, we cannot
let this waste continue and still maintain
an effective fire pressure for hydrants,
even though we had an indefinite quan-
tity in our reservoirs. The.pipes are too
small so long as everybody is drawing ad
libitum from them. You cannot play
streams forty feet high from the hydrants
in many parts of this city.

The hotels and large manufactories
use enormous quantities of water, mainly
legitimately, but if thousands of private
users are running three gallons to waste
for every one gallon really used, these
hotels and manufacturers are unjustly
compelled to pay more than double what
water ought to cost, and more than
double what everybody else is paying.

The cause of all this is that city coun-
cils, in selling water to the community,
do not make each person pay alike
for the quantity used, and at the cheap-
est rate, and prevent him from getting
Vol. XXV1L— No. 3—16.

more than others are entitled to who pay
the same.

Apply to gas the same system that is
applied to water, and you would bank-
rupt every gas company in existence.
Many people would never trouble them-
selves to turn off the gas, but let it burn,
if it costs no more whether it burns or
not.

The remedy for existing abuses is to be
found in making users responsible by
measuring the water used through proper
water meters. Then, if they wish to
waste it, let them pay for it. The result
would be to cut down the waste of sixty
per cent., and this would be equivalent to
doubling the water works.

In answer to the objection sometimes
urged against reducing the supply of
water to a reasonable basis, " that we must
let the water run continually in many
cheap buildings to prevent freezing of the
pipes," he said that when men put up
shambling tenements to make a large re-
turn upon a small outlay, it is unjust to
force the rest of the community to pay
for the tenement man's meanness.

The constant cry of the demagogue who
calls himself a practical man is, " Don't
stint the poor man !" But I do not wish
to stint any one. Ascertain how much
is actually needed, and then double it,
but stop the waste somewhere.

He advocated the plan of having the
city put one or more main meters on each
house, and then let the owner of a tene-
ment house put one upon each tenant,
and said that there are always a few diffi-
culties in the way of any improvement,
but they disappear before the light of ex-
perience.

The only important argument against
the adoption of a general water-meter
system has hitherto been that no meter
has been found sufficiently reliable under
all circumstances to be depended upon.
This has been, in the main, true, as
proved by experience.

In Providence, where water meters are
used, it is found that thirty per cent, of
them must be repaired every year, and
that the coming meter has not yet ar-
rived.

Water meters in use, up to this time,
are constructed upon two principles — the
piston and the rotary ; but in both cases
we are trying to make a tight vessel in
which to measure water by the mere con-

226

VAN NOSTRAND'S ENGINEERING MAGAZINE.

tact of two pieces of metal in movement
against each other. In both cases the
impinging or sliding of two surfaces of
metals against each other is involved, and
when two surfaces of metals rub together,
especially if there be mud or grit be-
tween them, as is liable to be the case in
water meters, they wear leaky.

It is not practicable to remedy this by
means of nicely-adjusted springs and
rings which require skill to keep them in
order, as a water meter must be left to
itself in exposed situations ; hence, the
entire system of piston and rotary me-
ters is fundamentally wrong in principle.

He next proceeded to sum up the req-
uisites for a water meter, stating that
they should be :

First, It must not wear or corrode, so
as to allow water to pass through it un-
registered.

Second. Its action must not be affected
by mud — a terrible element for water
meters.

Third. It should not let water that
has once passed through it into the house
pipes return again to the street mains, to
the loss of the consumer. This is a fault
with nearly, if not quite all meters in
use. You can see how it affects the con-
sumer, say in New York, and even in this
city in certain localities, where, after ten
o'clock in the morning, when everybody
is drawing, you cannot get water above
the second story of the buildings in such
district. At night the water mounts
higher to fill the pipes, and is registered,
then descends and remounts, and is
registered with every variation in press-
ure ; consequently, a certain large per-
centage of water is registered over and
over again.

Fourth. A water meter should have no
stuffing boxes or gearing to wear out and
get leaky, nor springs or cranks which
corrode and get out of order.

Fifth. It should not make objectiona-
ble noise or produce concussion in the
pipes, as the pipes, when suffering them-
selves from constant shocks, also conduct
the noise over the house.

Sixth. It should be able to withstand
the rudest shocks and violent changes.

Seventh. A water meter should present
but the smallest obstruction to the flow
of water. There are many meters in use
which reduce the flow of water from ten
to forty-five per cent.

Eighth. It should deliver water with a
smooth and even flow — an absolute con-
dition where fountains or motors are de-
sired.

Ninth. The expense for maintenance
must be trifling.

Tenth. The parts must be simple, dur-
able and cheap.

Of the hundreds of attempts to pro-
duce a good water meter, no more than
half a dozen have been found to approach
in practice anything like success, and
only two or three have been found by
water boards to be worthy of adoption.
But the city of Providence finds that
thirty per cent, of all the meters were
taken out and repaired during the year,
and the Chicago report says that one
thousand piston meters cost $17,000 for
repairs in nine months' time, thus show-
ing that the best types of meters thus
far employed were unsatisfactory in du-
rability, requiring great expense for re-
pairs, and causing great annoyance to
consumers by interruption of supplies.
They have also been very inaccurate,
over-registering and under-registering
under various pressures.

Mr. Coleman next explained the reasons
why these imperfections should be ex-
pected in piston or rotary meters, and
then said :

The true principle upon which a real
water meter depends seems to me to be
contained in a quart pot. It is a tight
vessel ; you fill it and empty it, refill and
empty, and there you have an exact
measure. If you have an india-rubber
bag, and fill and empty it, you have the
same principle of exact measurement.

The Spooner diaphragm meter is con-
structed on this principle. It is formed
of two chambers, the upper one contain-
ing the valve mechanism, and the lower
one actuating the diaphragm and discs.
The valve shaft, which passes through
the valve chest, carries three valves, .the
center one being double faced. The
valve chest is divided into three compart-
ments, with four parts ; thus, at each
movement of the valve shaft, two ports
are closed and two are opened, admitting
the water to the measuring chamber on
one side of the diaphragm, and allowing
the water on the opposite side of the
diaphragm to pass out of the meter. The
lower or measuring chamber is divided at
the center by a diaphragm of india rub-

TIIK WATKK-M l TKK SYSTEM AND WATEB METERS.

'227

ber, moulded into concavo - con vexed
form.

The edge of the diaphragm makes the j
packing between the two eastings form-
ing the chamber. On each side of the
diaphragm there is a perforated disc,
with the edges curved backward, so that
all wear of the diaphragm against the
disc is prevented On the back of each
disc there is a projection which rests on |
a stud, which is fastened to the shell of
the meter, the disc sliding forward and
back, moving in its action the lower end
of the levers.

On the outside of the casting forming
the upper chamber is placed the register-
ing mechanism, actuated by one end of a
lever that enters a recess in a horizontal
moving bar ; the other end of a lever en-
ters the chamber, and is worked by the
moving parts of the meter.* The water
enters from the supply pipe into the up-
per compartment, and passes thence
through an open port to, say, the right-
hand side of the diaphragm, which it
moves slowly towards the left disc, forc-
ing it against the lower end of the valve
lever, thereby reversing the position of
the valves and changing the flow of water
to the other side of the diaphragm, when
the operation of the moving parts of the
meter exactly reverses. While the water
is passing into the measuring chamber
on one side, precisely the same quantity
of water is being discharged from the
opposite side of the diaphragm, the flow
being smooth and without interruption.
The meter discharges a uniform measure
of water at each movement of the dia-
j)hragm under any variation of pressure.

Mr. Coleman claimed that this meter
possessed the requisites for a water meter
which he had already enumerated, and
then said : It may be proper to say that
my attention was called to this meter on
my return to this country last autumn,
and a request made that I should ex-
amine it professionally as a piece of
mechanism. I did so, but insisted upon
making a series of trials before giving a
report upon its merits. Through the
kindness of the Water Board of Boston,
we gave it long and exhaustive trials ;
and subjected it, among others, to the
following unusually severe tests :

1. The rapid opening and shutting of
the supply cocks under a full head of
water made no difference in its accuracy.

2. The water was permitted to drop
slowly from the outlet for fifteen hours,
and at the end of that time we found six
cubic feet of water in the tanks, and six
cubic feet were registered on the dial.
The Water Department reported a varia-
tion of about two per cent, under a very
small How, but this is readily accounted
for by the air contained in the water.

In addition he presented the opinions
of other water engineers in its favor, and
then said : If we have succeeded in pre-
senting any arguments which have con-
vinced you that the water-meter system
is the proper method of selling water, I
trust you will believe, as I do, that the
meter invented by Mr. Spooner is an in-
strument upon which municipal corpora-
tions may safely rely for accuracy and
thorough durability, as well as for all of
the good qualities which are indispensable
in a water meter.

In answer to certain questions, Mr.
Coleman said that the diaphragm is com-
posed of pure rubber without any fabric,
and hence is very durable. Any mud or
sand that might accumulate is washed off
by the water, since the diaphragm and
the valves are vertical. The points that
have to exert thrust are bushed with hard
rubber and brass to prevent rust from
blocking up the joints. They have been
carefully testing it thus far, wishing to
be sure that it was accurate and durable
before asking corporations to adopt it,
and the last patents were secured only
four or five months ago ; but the tests to
which the meters have been subjected
have been of extraordinary severity. He
also stated that one of the meters con-
structed during the experimental stage
of the invention has been in constant and
successful use in Syracuse, N. Y., during
the last six years.

Recently, says the Engineering, the
firm of Sir W. Armstrong & Co. has sub-
mitted for trial a breech-loading gun hav-
ing a peculiar construction. The whole of
the piece in rear of the trunnions is built
up of steel wire, over which is shrunk
ordinary yet thinner coils of great te-
nacity. It is said to be capable of bearing
an explosion of 300 lbs. of slow- burning
service powder. Although the weight of
the gun is only 21 tons 4 hundred-
weight, it has a bore of 10.238 inches.

228

YAN NOSTRAND'S ENGINEERING MAGAZINE.

DISCUSSION OJST THE ANALYSIS OF POTABLE WATER.

By CHARLES WATSON FOLKARD, Associate Royal School of Mines.
From Proceedings of the Institution of Civil Engineers,

II.

DISCUSSION.

Dr. Tidy said, in discussing the ques-
tion of water supply, it was important to
grasp its many-sidedness. When it was
desired to supply water to a town, various
possible sources were selected, and sam-
ples were sent to a chemist, whose duty
it was to analyze them. It was not for
the chemist, however, to say whether the
water was pure or impure. To him,
pure water was hydrogen and oxygen,
nothing else. To him, 1 cubic inch of
dissolved gas, or 1 grain of dissolved
matter, were impurities. The chemist
had only to say what was the composi-
tion of the water submitted. From the
chemist it passed to the sanitarian, the
medical man, whose view of the subject
was essentially different from that of the
chemist. With the analysis in his hand,
he had to ask himself if 1;he water was
likely to be a proper one for the supply
of the town for which it was proposed.
He could not experiment with the water,
but he endeavored to ascertain where
waters of a similar kind had been sup-
plied, and what had been the result.
That was the medical aspect of the ques-
tion. It then passed to the engineer. It
having been decided that the water was
good, the engineer asked himself, "Is
there sufficient to supply the town, and
are the conditions such that it can be de-
livered at a moderate cost?" That was
the engineering aspect of the question.
It was essential to his purpose to separ-
ate these three. In criticising the paper,
perhaps somewhat severely, he might be
permitted to say that he had had some
experience in water analysis. Without
reference to the time during which he
had been in practice for himself, he had,
during the many years that he had as-
sisted the late Dr. Letheby, made nearly
four thousand analyses of water with his
own hands ; and as a medical man he had
also had something to do with the sanitary
aspects of the question. He would not
discuss the various processes of water

analysis, which he had himself dealt with
at considerable length elsewhere. The
author had stated that chemists were
"powerless to help the sanitarian in dis-
criminating between wholesome and un-
wholesome water." Dr. Tidy did not
pretend to say that the chemist could do
everything, but he maintained that, given
a reliable analysis of water, the chemist,
or rather the sanitarian, was able to
speak with almost unhesitating certainty
in bringing it to bear on the sanitary
question. What were the means by
which to arrive at a true chemical knowl-
edge of the composition and properties
of water? He admitted, with the author,
that the varieties of organic matter in
potable water were somewhat numerous ;
chemists therefore, did not conduct a
water analysis with the same certainty
as they did a quantitative analysis
of a body, with the exact con-
stitution and composition of which
they were familiar ; but considering that
two out of the four processes described
in the paper, vastly different as they were
in their action, closely agreed in their
results, he thought the public might
reasonably have some faith in these as
a means for estimating the organic matter
in potable water. As he had shown be-
fore the Chemical Society, with reference
to nearly two thousand cases of water
analysis treated by the combustion proc-
ess of Dr. Frahkland, and by what Dr.
Tidy had called the oxygen and others
the permanganate process, the actual re-
sults were as nearly as possible identical.
A report would shortly be issued by him-
self, Dr. Odling, and Mr. Crookes, On
London water. No fewer than three
hundred waters had been examined by
both these processes, and by means of a
series of wave diagrams it would be
shown how closely they agreed in the
story they had to tell. The author's
statement that the chemist was powerless
to help the sanatarian was a very strange
one, coming from a chemist. What were
the reasons he assigned for this power-

DI80US8ION ON Till. ANALYSIS OF POTABLE WATER.

229

lessness f In the first place he stated
that " it is an ascertained fact, proved
beyond possibility of doubt, that mere
dilution, how far soever it be carried,
does not render inoperative the specific
action of living germs" (p. 11). His
second reason was that uthe germs
which cause or accompany disease are en-
dowed with the most persistent vitality,
and are capable of withstanding heat,
cold, moisture, drought, and even chemi-
cal agents, to a marvelous extent " (p.
12). That was all very well, but where
were the germs f In only three diseases,
pig-typhoid, remittent fever, and splenic
fever, had anything of that nature been
detected. No such thing as a typhoid
germ had been discovered. One could
no more analyze a water for the germ
of typhoid, than one could analyze
the brain for an idea. Not only,
however, did the author speak of germs
as though they were tangible, but
he had fixed the conditions of the life
of a thing the very existence of which
had never been proved. As to whole-
someness, the author expressed his be-
lief that the only safe test was by trac-
ing the water to its source. What
source ? He doubted whether there was
a particle of water in creation that had
not passed through an animal body once
or more. For himself, looking at the
subject as a medical man and as a chem-
ist, he believed the true test was not
what the water was, miles off, but what
it was at the place at which it was pro-
posed to be taken for supply. That was
the practical method of testing it, and it
was a. method always adopted in other
matters. Engineers should not trouble
themselves about what the water was 50
miles off, or fifty years ago, but consider
what it was afc the time and the place
where it was proposed to take it. The
author, naturally, with his views, con-
demned all rivers. He did not mince the
matter, but said, " This will at once con-
demn all rivers flowing through a popu-
lous country" (p. 12). And he added, by
way of illustration, " Take, for example,
the case of a river with a town of 50,000
inhabitants on its banks. If supplied ,
with water at high pressure and sewered, I
the amount of foul water discharged into
the river will be about 1,000,000 gallons
daily, irrespective of the rain-fall, which
will bring with it the washings of the

streets, &c. Taking the total flow of the
river at 500,000,000 gallons, and suppos-
ing that the water is perfectly pure when
it readies the town, there will be a mix-
ture of 1 part of sewage in 500 parts of
clean water, for the inhabitants of the
next town to drink. Take now an in-
fected liquid and add 1 part to 500, or
even to 500,000 parts of liquid suscepti-
ble of infection. The mixture will swarm
with lop organisms and become putrid in
few days, provided only the conditions
are favorable " (p. 13). Then he asked,
" What may be expected to happen to
the unfortunate inhabitants of the lower
town ? Simply this, that the strong and
healthy will have sufficient vitality to
throw off the poison, but the weak and
sickly will succumb, inoculated by the
dejecta of zymotic patients in the upper
town." '• The above," said the author,
"is no fanciful picture." Fanciful was
not the word for it, and he hardly knew
a word to express it, but certainly a more
far-fetched picture, a more unbridled
effort of the imagination, he had never
come across. He wished to ask the
author to explain how it was that, in the
case of towns affected with cholera on
the banks of rivers, having regard to the
period at which the outbreak of cholera
occurred in those towns, the disease had
invariably gone up the river and not
down. He challenged the author to pro-
duce a case in which the passage of
cholera had been without a break down
a river. The only case given in the
paper of injury from river water was one
in which the experiment of drinking
polluted water had been tried on the in-
habitants of a town in Surrey. He
thought he knew the town to which the
author referred, and if he was right in
his presumption, the case was one in
which he had been himself consulted
professionally, and he believed also Dr.
Frankland. They had both written a
report, and he was prepared to show if
necessary, that the illustration in ques-
tion had nothing whatever to do with the
subject. The author had further stated
that there was not the least evidence
to show that foul water was rendered
wholesome by flowing 50 or 100 miles.
Dr. Tidy maintained that a distance of
10 miles was sufficient for the self -purifi-
cation of water under proper conditions.
A few weeks ago Dr. Dupre and himself

230

VAN NOSTRAND'S ENGINEERING MAGAZINE.

had seen a wonderful illustration of the
self -purification of water within a very
much shorter distance. Turning to the
sanitary aspect of the question, he would
remind the members that in England
there was a large number of towns sup-
plied with well water, and a large number
supplied with river water. He had taken
the death statistics for ten years of thirty-
six of the largest towns in England,
eighteen being supplied by deep well
water, and eighteen by river water. The
eighteen towns supplied by well water
had a population of 889,340, and the
eighteen towns supplied by river water
had a population of 911,742. The aver-
age death rate of the towns supplied by
wells was 22.72 per thousand, and the
average death rate of the towns supplied
by river water was 22.66 per thousand.
In fever and some other diseases there
was (except in certain cases that could
have nothing to do with the water) a
decided advantage on the side of rivers.
It might be said that he had taken a
number of towns indiscriminately and
mixed them up together. To meet that
observation he had examined the death
statistics of London, as" Mr. Baldwin
Latham had done. He had gone care-
fully over Mr. Latham's figures, brought
them down to the latest date, and elab-
orated them somewhat more fully. Lon-
don was supplied by eight companies,
five of which derived their supply from
the Thames, one from the Lee entirely,
and one from the Lee and from wells
(the New River Company), and lastly,
one that derived its supply exclusively
from deep wells in the Chalk. The death
rate for ten years of parts supplied by
river water was 21.57, whilst that of
the places supplied by deep chalk wells
was 21.48. He had gone through the
various diseases, and had found that
while certain diseases, such as croup
(which he thought could scarcely be
traced to water), appeared to be a little
more prevalent in the river districts, cer-
tain other zymotic diseases were some-
what in excess in the districts supplied
by wells. It had been proved before the
Duke of Richmond's Commission by the
experiments of Dr. Frankland and Dr.
Odling jointly, and these experiments
had been since repeated, that at Hamp-
ton the river contained if anything less
organic matter than the water at Lech-

lade, where the Thames first assumed
the condition of a river. That water
purified itself in a running river he was
as certain of as he was of his own exist-
ence. And this self-purification was
effected first by the process of subsi-
dence, the solid matter in the water being
carried down ; secondly, by the process
of oxidation (the oxygen being partly
derived, no doubt, from the air, and
partly from plant life) ; thirdly, by the
action of fish. He had no doubt upon
that point, and he spoke with a knowl-
edge of many of the important rivers in
England and Ireland. In conclasion, he
desired to ask the author a few questions.
First, admitting the complexity of the
organic matter in potable water, and that
the true test of the value of different pro-
cesses for its estimation was consistency
in their results, had the author ever at-
tempted to prove or disprove such con-
sistency ; and, if so, could he favor the
institution with the details of those ex-
periments ? Secondly, admitting his
theory of rivers being such important
agents in spreading disease, would he
explain how it was that in outbreaks of
cholera where towns had been affected
along the banks of a river, the order of
attack had been invariably up the river,
and not down? Thirdly, would he ex-
plain, in view of his alarming picture,
how it was that towns supplied with
river water showed no greater general or
zymotic death rate than towns supplied
with deep well water ; or if he stated that
which was not true, would he bring for-
ward facts to contradict it ? Would he
explain, further, how it was that in- Lon-
don the parts supplied by the Kent
Water Company showed an almost iden-
tical general and zymotic death rate with
those supplied by the waters of the
Thames and the Lee ? Fourthly, admit-
ting that there might be germs in run-
ning water, could he adduce any evidence
to show that under natural conditions of
flow and contact with oxygen they were
not amenable to the same laws as organic
matter generally ? He would only say
that if t the chemist desired to gain tthe
respect of the engineer or of the sani-
tarian, he must not indulge in far-fetched
and fanciful theories or hypotheses, but
confine himself strictly to the arena of
facts.

Dr. Thudichum said when important

DISCUSSION ON THE ANALYSIS OF POTABLE WATER.

281

questions were concerned, and one had
a strong conviction to state, it was not
easy to find a form in which to make that
conviction acceptable. Nevertheless, he
hoped to make himself intelligible on
some of the main points which he de-
sired to illustrate. He congratulated
the author on having made on the whole
a clear, succinct, and practical statement.
No doubt it required on his part a great
deal of courage as a chemist to come
forward and tell his brother chemists
that they were groping in the dark, and
that their analyses were valueless. If
chemical analyses of waters were to be
discredited, Dr. Thudichum would feel
much regret ; but there was a great deal
of truth in what the author had said. It
had been stated by Dr. Tidy that he had
latterly come to the conviction that Dr.
Frankland's analysis of water was as
good as his own. If the members had
been present at the meetings of the
Chemical Society, when that matter was
discussed, they could hardly have be-
lieved what had since taken place.
Neither having convinced the other as to
the uselessness of his particular mode of
analysis, they at last became friends,
and said to each other, " Your analysis is
as good as mine ; let us embrace and be
friends. " What did those analyses mean ?
They ascertained that a certain amount
of organic matter was present in water
intended to be drunk, but they showed
no more. The organic matter, for ex-
ample, contained in Thames water could
not be shown to be noxious to health.
Chemists had not shown at what par-
ticular concurrence of conditions they
were to begin to consider water injurious
which contained a certain amount of or-
ganic matter, and under what circum-
stances it was to be considered whole-
some. Waters taken from sources like
rivers always contained organic matter,
because they were always flowing over
large surfaces clothed by vegetation,
living or dead, and under all circum-
stances there was a certain amount of
dead, organic, vegetable matter present
in watercourses. How innocent the
organic matter of the river Thames was
he had proved in this way. He had sent
to the places where the water companies
took their water, and caused to be col-
lected a large amount of organic matter,
earned it to his laboratory, infused it

with distilled water, and allowed it to
stand a certain number of hours. He
then analyzed it, and found what he ex-
pected, that this distilled water had as-
sumed, with regard to organic matter,
the properties of Thames water. He
therefore maintained that the analysis of
water, with reference to the quantity of
organic matter contained in it was, hy-
gienically speaking, of no value. The
next point to which he desired to refer
was the bearing of the results of biologi-
cal and microscopic research on the sub-
ject under consideration. That led to
the point on which the whole argument
oscillated. Under what circumstances
was water wholesome, and under what
circumstances was it unwholesome ?
There might be waters which contained so
much inorganic matter as to cause di-
arrhoea, but such waters would be so un-
palatable that they would not be drunk.
On the other hand, there might be
waters perfectly clear and palatable in
which the chemist would discover no
appreciable amount of organic matter,
and yet they would carry death where-
ever they were consumed. That was the
biological aspect of the question, and in
regard to that aspect microscopic art was
just as impotent as chemical art to de-
termine whether water was wholesome
or not. Then what test could be ap-
plied to ascertain the fact? There were
various tests, some of which had been
unpremeditated. For example, when in
the East of London cholera swept along
the river Lee and attacked twenty thou-
sand persons, that was an experiment on
a large scale. When again in the South
of London two companies rivaled each
other which should proceed in the most
successful way to distribute cholera
amongst their consumers, as in 1848 and
1854, other examples were made on a
large scale. If another example was re-
quired, showing how water might be con-
taminated without microscopists dis-
covering it, the case of the poisoning of
Caterham Well might be taken, by means
of which .three hundred and fifty- two
persons contracted typhoid fever, be-
cause a small amount of excrement from
a sick person who was allowed to work
in the well got mixed in the water.
Under such circumstances it was neces-
sary to see with an eye which was not mi-
croscopic, and to apply a certain argument

232

VAN NOSTRAND'S ENGINEERING MAGAZINE.

which was not chemical, but which was
hygienic or medical. "Water might be
bright and brilliant, and yet contain the
germs of death in it. It was well known
that things might have organs and a
certain chemical composition, and yet
not be visible to the eye. Take the case
of a minute drop of blood ; put it on a
microscopic slide, and add water to it.
All the corpuscles were before seen to be
red, and their shapes were distinguish-
able, but after the addition of the water
the coloring matter was withdrawn, and
no power of the microscope could make
them visible. Here was a case in which
an organized body of the diameter of
of a milimeter could be rendered

10 0 0

invisible, and how much more might that
be the case with a body having perhaps
not 10500 part of the diameter of a blood
corpuscle ? He referred to those germs
which in the last thirty years had been
proved to exist as the causes of zymotic
diseases. He would refer, as an illustra-
tion, to the germ of the fowl-cholera.
It was as distinct a germ as could be
made out, visible under the microscope,
having spores, still minuter particles,
which were to the bacterium as the seed
was to the plant. If those germs were
preserved for a certain time in a closed
tube, a cloud would at first be seen, but
as the oxygen in the tube was removed
and consumed, the germs assumed a dif-
ferent shape and appearance ; they were
lost to sight altogether. How were they
to be found out? Not by the micro-
scope, not by chemistry, but by taking
a needle and dipping it into the liquid,
which was perfectly transparent, and
then inserting it in the cutaneous tissue
of the fowl, and in a few days the fowl
would be dead. It was impossible to
experimentalize with water merely, so as
to show whether it was wholesome or
not. What then followed? What hy-
gienists had always maintained, that
water should be taken from natural
sources which were neither contaminated
nor contaminable, and those should be
the only sources of drinking water for
communities and individuals. Could this
proposal be carried out ? Of course it
could. In the neighborhood of London,
for example, taking a circuit of 30 miles,
100,000,000 gallons of spring water could
be found running every day, which
would be amply sufficient to supply the

culinary and drinking wants of London.
In the neighborhood of Hertford, for in-
stance, there was a spring yielding
10,000,000 gallons a day. It ran into
the river Lee, and there would be no
practical difficulty in taking it out of the
river, and sending it direct to London,
without allowing it to be contaminated
by dung-boats and all the filth that ac-
cumulated in the river. The citizens of
London, who first attempted to supply
the city with water, did not go for river
water, but for spring water, and it was
for the conduction of spring water to
London that they got their first Act of
Parliament. In like manner, engineers
should set about it now, everywhere get-
ting all the spring water they could to
supply towns. They would find in every
neighborhood a sufficient supply to sat-
isfy the public wants. London, of course,
would require a double supply, according
to the proposal worked out by Sir
Joseph Bazalgette, Mr. Easton, and Sir
F. J. Bramwell, a proposal which had
his greatest admiration. It should not
be imagined that because it was strange
it was unparalleled. In fact an example
might be found in a town having much
more limited means than London. He
held in his hand a report by the Govern-
ment of Wiirtemberg on the public
water-supply of that kingdom, a king-
dom which he believed was at the head
of civilization in regard to that question.
In the capital, Stuttgardt, there were two
supplies, one of common water for water-
ing the streets, filling baths, and flush-
ing closets, and another for drinking
and cooking. Numerous instances might
be cited from that report of the care
taken to supply even the lowest classes
of the community. Even the villages on
the highest mountains in the B-aue Alb
were supplied with excellent spring
water, to the extent of 60 liters per head
per day. , It was pumped to the height
of 310 meters, and the pressure in the
pipes was 75 atmospheres. If a small
village of that kind could be supplied
with pure spring water, would not the
richest town of the richest nation in the
world be able to get the same security
against disease ? The dangers threaten-
ing were very great. Perhaps not once
in ten years would a river carry disease
massively in its water, but if it did so
once in a century it should be provided

DISCUSSION- ON THE ANALYSIS OF POTABLE WATER.

233

against. The water from the downs of
Hampshire eame filtered through hun-
dreds of feet of chalk. It was of the
greatest purity, cool, and haying no or-
ganic contamination of any kind, and if
it wore taken through pipes to the con-
sumer in London, under a system of

ustant supply, all danger would van-
ish ; but if tho towns continued to be
supplied with water from rivers, there
would certainly be, on some occasion or
other, a failure of nitration, the intro-
duction of disease, and a repetition ofthe
fearful and melancholy lessons of the last
thirty years, during which one hundred
thousand people had been crippled, and
not less than twenty thousand had died
from poisoned water. With the qualifi-
cations he had mentioned he had fu'ly
agreed with the author, and thanked him
for having afforded an opportunity of j
discussing so important a question.

Mr. Homeksham said for more than !
thirty years he had been in frequent
communication year by year, with analyt- 1
ical chemists and microscopists in re-
spect to the examination of water from j
different sources, to make selections for
the supply of water for drinking and do- j
mestic uses. Many of those men, some i
of them personal and intimate friends of i
his own, as Clark, Graham, Lankester, !
Miller, Newport, Ronalds, Thomson, and
Ure, were no more. From frequent !
communication with these, and still more
frequent communication with others who
remained, and from experience gained in
designing and carrying out various
works for the supply of different towns
and places with water for domestic use, |
not only in the United Kingdom, but on
the Continent of Europe, and places
more distant, he was pretty familiar with
what had been urged for and against
waters derived from different sources.
He made that statement to ask for in-
dulgence, in case he should appear to
speak somewhat dogmatically. With re-
gard to the paper, it appeared to him
that the word "previous" in the title
had been unnecessarily added. For
practical purposes, the point to be de-
termined was the amount and the qual-
ity of sewage or other present injurious
contamination, if any, in water for pot-
able and domestic uses. Such water
should be (1) at all seasons clear, trans-
parent, bright, and, when seen in large !

bulk, pore blue, that being the natural
color of nneontaminated water; ('2) well
aerated, holding in solution from 7 to 8
cubic inches of air per gallon, consist-
ing of 2 or more cubic inches of oxy-
gen and (5 of nitrogen ; (3) it should
have at its source a uniform temp-
erature equal to the average of the
climate for the year, which in this coun-
try varied but little from 50° Fahren-
heit ; (4) should be free from living
organisms, vegetable and animal, and
from all dead decomposing organic mat-
ter, and should not dissolve lead ; (5)
should hold only a moderate quantity of
mineral matter in solution, and thus be
soft and not deposit a coating of lime or
magnesia when being boiled. On the
subject of potable water, he thought it
was very questionable whether many
persons drank cold water from choice.
Where it was drunk at all, it was among
the lower classes who unfortunately could
not help themselves. When boiled it
was drunk to a large extent, as in tea
and coffee, and it was very largely used
in culinary operations, and it was im-
portant that water used for such pur-
poses should be such as did not deposit
fur in boilers or tea-kettles. Uncon-
taminated spring- or other water, derived
from a considerable depth below the sur-
face of the earth, was the only water
that at its source had a normal even
temperature at all seasons, summer and
winter, and, as far as he knew, was also
free from living organisms, vegetable and
animal. It was also difficult to find any
water but spring or subterranean that
was at all seasons clear, transparent,
bright, and when seen in large bulk, blue.
Water derived from brooks or rivers, or
from lakes, natural or artificial, varied in
temperature at different seasons of the
year, being comparatively warm in sum-
mer and cold in winter ; it was more or
less opaque, and when seen in bulk
lacked the blue color peculiar to uncon-
taminated spring-water ; it had in solu-
tion in warm weather less oxygen gas
than spring-water ; it held partly in sus-
pension and partly in solution, after
rains in hot seasons, manure washed from
land and droppings from animals ; and
it also abounded in life, vegetable and
animal, and was liable to inoculation by
means of drains with the virus of specific
diseases, causing ill-health and often

284

VAN NOSTKANIXS ENGHSTEEKING MAGAZINE.

death to those who drank it. He agreed
with the author in thinking that when
samples of water from different sources
were submitted to mere chemical anal-
yses, it frequently happened that the
results gave very little clue to their
wholesomeness, or the contrary. He
said very little clue, because there could
be no doubt that chemical analyses often
did give some clue, but in other cases it
gave none whatever. Chemical, and only
chemical, analysis could be relied upon
to determine the quantity and quality of
the gaseous contents of the water, the
mineral contents and consequent hard-
ness. The brightness, color and trans-
parency of the water could be judged by
the sight. Chemistry threw little light
upon the nature, quantity, and quality of
the organic matter that might be dis-
solved or mixed or lived in waters. Sup-
posing, and this was common with river,
lake and other surface waters, a water to
contain a large quantity of minute or-
ganisms, say several species of living
plants and animals, and several hundreds
of each species in half a gallon, the
chemist boiled all those plants and ani-
mals with the water, and after evaporat-
ing the liquid he weighed the residue,
and then subjected it to a process of
cremation. As the small animals and
plants were composed of more than 90
per cent, of water, the loss in weight of
the residue after cremation must be mul-
tiplied by 10 at least to arrive at their
weight when alive. As to the names, or
peculiar forms or qualities, wholesome-
ness or un wholesomeness, of the plants
and animals, chemistry, to use the words
of the author of the paper, was " power-
less to help the sanitarian." Knowing
that, it had been his practice during the
last thirty years to submit samples of
water, not only to an analytical chemist,
and thus obtain all the assistance that
could be had from chemical science, but
to submit also samples to a competent
microscopist and medical man well ac-
quainted with the forms, names, habits,
and other properties of the animal and
vegetable organisms pervading many
waters. The practical importance of
such microscopical examination would be
evident from the following considera-
tions. It had been well established that
when certain microscopical plants of the
nature of bacteria pervaded a water, to

drink such water often gave rise to
remittent fever, splenic fever, and pig^
typhoid. Chemistry was unable to dis-
cover these microscopic plants ; but a
competent medical practitioner acquaint-
ed with the properties and habits of
those minute organisms could detect at
least many of them and others of differ-
ent kinds. In June, 1852, both the late
Dr. E. Lankester and Dr. Redfern, the
present professor of anatomy and physi-
ology in Queen's College, Belfast, found
from thirty-two to thirty-eight species of
microscopic organisms, some plants, some
animals, and some diatomacese, besides
large numbers of each species in half a
gallon of water, drawn direct from the
supply pipes of the Lambeth Company
(taking its supply at Thames Ditton),.
before entering any house cistern. In
1857 Dr. Hassall, in a report to the then
President of the General Board of
Health, stated that any water drawn
direct from the mains of each of the
waterworks under the provisions of the
Metropolis Water Act, 1850, still con-
tained considerable numbers of living
vegetable and animal productions belong-
ing to different orders, genera and spe-
cies, but especially to the order or tribes
annelidse, entomostracese, infusorise, con-
fervese, desmideaB, diatomacese, and fungi.
Dr. Hassall stated that the examination
was made in. winter, and that other
examinations should be made in spring,
summer and autumn. No such further
examinations, however, had been made
by order of the Government. That, he
thought, was a great dereliction of duty
on the part of some department. Win-
ter, it was suggested, was not the time
to find the plants so well as summer and
autumn, yet no other authorized examin-
ation had been made. The waters of the
various companies were subject only to
chemical examination. In the last Re-
port of the Government Water Examiner
under the Metropolis Water Act, 1871,
a chemical analysis was , given by Dr.
Frankland, another by Messrs. Wanklyn
and Cooper, and another by Drs. Bernays
and Tidy. In that report, there was no
mention of microscopical examination.
If microscopists were employed to ex-
amine the water month by month they
would find out the species that were
more frequent at one season than an-
other, and ascertain in what water they

DISCUSSION ON Till: ANALYSIS OF POTABLE WATER.

235

abounded. It was well known by those
who had paid attention to the subject,
that many classes of those plants and
animals indicated unwholesome water,
and that these were mostly to be found
in warm weather. It was true that Dr.
Frankland, with his analyses, reported
that the Grand Junction Company's
water contained moving organisms, but
no particulars were given ; while in the
reports of Messrs. Wanklyn and Cooper
and of Drs. Bernays and Tidy the pres-
ence of any organisms was ignored.
That reminded him that only the other
day a shareholder who wrote in the
21i?nes newspaper stated that the com-
pany was satisfied with the report of its
chemists, because they did not mention
any living organisms ; but it was not
because there were none, but because no
microscopists had been employed to
detect them. Surely if it was worth
while to have the companies' waters
chemically analyzed once per month by
five professors of chemistry, it should be
made a point to have at least one exam-
ination of the waters in a month by a
competent biologist and microscopist.
In obtaining samples of water from dis-
tributing pipes for determination of the
organic contents, the water to be exam-
ined should be drawn not only direct
from a main but near to the " dead end,"
as it was technically called, of a rider
pipe, or to the dead end of a service main
placed in a side street, for the organisms
existed in much larger quantities near
the dead ends of mains than in circulat-
ing mains. The creatures were so intel-
ligent that where they found the water
quiet they went to live and breed. Chem-
ists sometimes asserted that water had
not been properly filtered. Filtration in
some respects really injured the water in
summer, because during the process
there was collected on the top of the
sand a further quantity of organic mat-
ter that became decomposed, and fur-
nished pabulum for the insects. The
author had stated that reservoir- or lake-
water contained but a small quantity of
organic matter, but he did not agree
with that statement. It would be found
by the Registrar-General's Returns that
wherever lake-water was supplied to a
town there was an excessive mortality.
But, putting that aside, as there were
many other things to cause mortality

besides impure water, yet such things as
the excreta of animals, liquid and solid,
leaves and the like were unavoidably
washed into the water. Water con-
tamination in lakes also arose from the
formation of mud on their unlined sides
and bottoms. It was impossible to pre-
vent the formation of this mud, which
was congenial to the production and
growth of animal and vegetable life.
The water from Loch Katrine and the
water supplied to Manchester were full
of dead organic matter and living or-
ganisms, especially in the summer. The
author had further stated that very
slight contamination took place in water
when exposed in the open country ; but
he could not agree with that statement.
He remembered having a large reservoir
lined with cement on the South Downs,,
for the supply of Brighton. The water
was perfectly pure when pumped from
the wells and into the open clean reser-
voir, but in a few hours in the summer,
there were masses of confervae growing
on the top of the water, and soon after a
number of insects of different orders
bred and flourished in it. It was a
serious expense even to clear out the
reservoirs and keep them clean in the
summer. The evil could not be pre-
vented except by roofing them over.
Carbonic acid was given off from bicar-
bonate of lime, which formed the pabu-
lum that the spores of the confervse
required, and the consequence was the
water was polluted though the open
reservoirs were in the country. He had
seen open reservoirs in a hot day when
clouds of insects had been blown by the
atmosphere into and upon the water in
heaps. It was an entire mistake to sup-
pose that water could be kept pure in an
open lake or reservoir because it hap-
pened to be in the country. The tem-
perature of the Thames in a hot summer
was as high as 72°, and in the winter it
was as low as 35°. Water, when it was
warm, lost some of its oxygen, and plants
and animalcules bred in it to a much,
larger extent than when it was cold.
The loss of heat in winter, bringing
the water down to within 3° of freez-
ing point, rendered it liable to freeze
readily in the consumer's pipes, and
thus burst them. There was another
point on which he disagreed with the au-
thor, that water to be purified must un-

236

VAN NOSTRAND'S ENGINEERING MAGAZINE.

dergo a process of distillation by the
heat of the sun. Water that fell on up-
lands composed of porous strata, such as
sandstone, chalk, &c, was absorbed and
percolated downwards often to great
depths through the pores of the strata.
A quantity of water was held in the
pores by capillary attraction, and diffused
through its mass. The varying density
of the air brought the water thus held
by capillary attraction in contact with
changed oxygen, and by that process
long-continued deprived the water of
any organic matter it might have pos-
sessed. Supposing a depth of 18 inches
of rain to go down through the surface
in the course of a year, as the chalk
strata were on an average more than 600
feet in thickness, and one-third of the
bulk consisted of pores, it followed that
it would require a depth of at least 200
feet of rain, or the produce of one hun-
dred and thirty years, to saturate the
pores.

Professor Tyndall observed that Mr.
Homersham had had very valuable ex-
perience in regard to the subject under
consideration. He had gone with Mr.
PEomersham to Canterbury, and seen the
chalk-water there, and the mode of soft-
ening the water according to Clark's pro-
cess. He did not know that he had ever
seen a more beautiful experiment upon a
large scale. He had also seen the same
thing at the Chiltern Hills and at Cater -
ham, where the works were under the
supervision of Mr. Homersham. There
was one point, however, in which he was
inclined to differ from him, and to agree
with previous speakers. He was rather
doubtful as to the ability of a microscop-
ist, even though he were a medical prac-
titioner, to detect in water the germs
that were chiefly damaging to man. He
would take the case referred to by Dr.
Thudichum, and a more lucid medical in-
vestigation he had never known. There
was an outbreak of typhoid fever at Red
hill and Reigate, where more than three
hundred persons were attacked. Dr.
Thorne went there, got hold of the tag-
ends of his facts, fitted them together,
traced them backwards, and finally came
with the utmost certainty to a single in-
dividual who had been employed in sink-
ing the well at Caterham, and whose ex-
creta had infected the whole neighbor-
hood. Imagine the diffusion of the in-

fective matter through all those long
pipes, and a medical practitioner trying
with his microscope to find out the little
infected particles. In his opinion it
would be a hopeless task. In the case
of that most virulent disease, splenic
fever, which had been worked at so suc-
cessfully by Pasteur, the germ was eas-
ily seen. It was a large bacterium.
But there were bacteria that were' not
easily seen. He had, for instance, a cas-
cade near a little house on the Alps,
7,000 feet above the sea, and although it
was charged with water coming from the
snow-fields of the Alps, if he took a
speck of that clear water and infected an
organic infusion with it, in forty-eight
hours the infusion would become putrid
and swarming with organisms. He once
chose a piece of the clearest ice he could
find, placed it und^r the receiver of an
air-pump with perfectly moteless air
around it, and allowed it by fusion to
wash its own surface. From the heart
of that ice, clear as crystal, he took a
quantity of water, and gave it to Dr.
Burdon Sanderson, who found that it
contained germs of bacteria just as ef-
fective in producing putrefacation as or-
dinary water. He should not, therefore,
like to accept the notion that germs were
so easily detected by the microscope.
He agreed with Dr. Thudichum, that
chemical analysis would afford but little
information as to the deadliest things
that might be in water, and that the mi-
croscopist could tell very little about
them ; but that the best way was to draw
water supplies from sources where con-
tamination could not come into play, and
in that respect he desired to say that
Mr. Homersham stood conspicuous
among engineers.

Mr. Jabez Hogg remarked that, as a
microscopist of some experience he^
agreed in part with what had fallen from
Professor' Tyndall as to what the micro-
scope could do, and what it could not do.
He admitted that the microscope had
never disclosed the kind of bacterium
that would produce a specific form of
disease, but fye could not agree with him
that the microscope could not detect the
presence of bacteria. It could not per-
haps detect the exact formation of the
creature moving under the field of the
microscope ; but microscopists could say
something was there a little beyond their

DISCUSSION ON THE ANALYSIS OF POTABLE WATER.

237

ken, and medical men and physiologists
could carry it a little farther, and take
some of the supposed infective germs,
and produce a physiological action upon
the blood of an animal, and ill that way
confirm the suspicion that there was
something wrong with the water. As to
the particular method to be pursued and
carried out in researches of the kind, he
was pleased to find the Local Govern-
ment Board bringing its authority to the
elucidation of this point. An independ-
ent body was taking steps that would
tend to set the vexed question of con-
tagion at rest. A very competent gen-
tleman was proceeding to make a series
of experiments to ascertain what amount
of significance could be attached to cur-
rent methods of chemical analysis of pot-
able waters. He took samples of water,
purposely polluted them with stools of
typhoid or enteric fever patients, and
compelled animals to partake of them.
The results already obtained were start-
ling, and sufficient to confound some
who were strong in their belief of chem-
ical analyses, and of those who persisted
in jumbling together the evidence of or-
ganic impurity and the evidence of un-
wholesomeness. In the first part of the
paper, various ways had been mentioned
in which water became contaminated.
He desired to point out the great neces-
sity for using precise terms in reference
to such matters. Dr. Thudichum had
spoken of spring-water. Spring-water
was water that many persons would not
like to drink. He supposed Dr. Thudi-
chum meant water drawn from subter-
ranean sources at great depths by an ar-
tesian well. If this were so, he might
be permitted to refer to the inquiry into
the Molesey irrigation scheme. It
would be remembered that the Molesey
people wanted to irrigate certain lands
with sewage, and it was discovered that
the Lambeth Company was drawing
2,000,000 gallons of its water daily from
a gravel-bed subsoil source at Molesey.
This underground water was discovered
when putting down conduits. The pipes
were found to be passing through an im-
mense body of water, and the engineer
thought he could not do better than
pump it up and use it, and call it spring-
water. This was done for a considerable
period, and it was supposed the Com-
pany were pumping deep well-water.

The water was submitted to chemical
analysis, and pronounced "perfectly
pure and wholesome ;" on closer investi-
gation, it was found that the water was
in a very bad and unwholesome state.
In the course of the judicial inquiry Mr.
Michael said : " This is neither more
nor less than diluted sewage of a most
dangerous nature?" The engineer re-
plied, " Oh no, it is not, for it has been
filtered and submitted to our chemist,
who pronounces it pure and wholesome
water." Among the chemists who pro-
nounced it to be pure and wholesome
was, he thought, Dr. Tidy. It had ap-
parently not entered into the calculation
of any one, that in drawing subsoil
water from an area of some extent (in
I this instance a radius of more than 1£
mile) the whole incidence of that area
must be taken into account. Now, it so
happened that at West Molesey it in-
cluded seven hundred and seventy cess-
pools, all of which were being pumped
dry, and mixed in with the Company's
water. A Government investigation
ended in putting a stop to that objec-
tionable mode of drawing a supply of
" spring- water."

Dr. Tidy said it was a mistake to sup-
pose he had certified to the wholesome-
ness of this water, on the contrary, he
had condemned it.

Mr. Jabez Hogg said he was glad to
hear the statement of Dr. Tidy, but he
knew that the chemists of the company
had expressed an opinion that the water
was perfectly pure and wholesome. He
could not for a moment doubt Dr. Tidy's
word, but there were one or two points
in connection with other of his state-
ments which he desired to notice. He
had contended that if the Thames River
water had a run of a certain number of
miles it would tend rapidly to oxidize
all the sewage mixed with it. " His re-
sults," he said, "were in accordance
with those of all the chemists who
had examined and reported on the
subject ; and he also believed that the
Thames in its flow of 130 miles as a
definite stream did not acquire any in-
creased proportion of organic matter."
If Dr. Tidy had examined the water at
Lechlade as well as 130 miles lower
down, but of which he afforded no evi-
dence, his remarks were apt to mislead.
From the first part of his statement it

238

VAN NOSTKAND'S ElNTGHSTEEKme MAGAZINE.

would appear that the Thames was as
pure at Hampton as at Lechlade, the
water not having acquired any increased
proportion of organic matter ; but the
results he had published did not show
the condition of the water in the river
130 miles below Lechlade ; they merely
showed its condition after it had passed
through the company's niters. Looking,
however, solely to the condition of the
water after it had been filtered, and ap-
plying Dr. Tidy's own theories concern-
ing the rapid destruction of organic mat-
ter, and which at Lechlade proceeded
from a scantily populated district, and
might be taken to be comparatively free
from sewage, all organic matter would,
according to his theory, have been de-
stroyed long before it reached Hampton ;
whereas that which replaced it, must
contain sewage contamination from nu-
merous populous towns from Lechlade
downwards. The organic matter, there-
fore, even if not large in amount, would
be worse in quality, and the water, of
course, inferior. In fact, all the towns
situated on the banks of the Thames
were constantly pouring in large quanti-
ties of sewage, and there coiild be no run
of more than 100 yards, to say nothing
of 130 miles, where pollution was not go-
ing on day and night. Who then could
undertake to say when and where some
typhoid or malignant fever patient would
not be sending excreta into the Thames
in a course of 130 miles ? Turn to the
report of a chemist who differed from
Dr. Tidy — the official water-analyst of
the Government, Dr. Frankland, whose
experience in such matters was beyond
all question. He had spoken in his
report of the improved condition of
London water, which he said was due
to the weather and to efficient filtra-
tion ; but Dr. Frankland's opinions
were still strongly adverse to the use
of Thames water for drinking pur-
poses, on the ground that it would not
be safe so long as sewage found access
to it. Actual danger might arise in the
production of diseases believed to be
propagated by organisms possessing a
remarkable degree of vitality ; and when
seasons conducive to an expidemic out-
break supervened, it was imperatively
necessary that water-pipes should not
become vehicles for the spread of disease.
The important point of divergence be-

tween Dr. Frankland and Dr. Tidy, who
were both working from the same data,
consisted, not in any marked difference
as to facts, but in a difference of opinion
as to the import of those facts. That
was a point which should be clearly un-
derstood and weighed when misleading
chemical reports were issued to the pub-
lic. Dr. Tidy of course fell back upon
the Registrar General's Reports, as show-
ing that there was no increase of deaths
in London ; but he omitted altogether to
take into consideration how much Lon-
don had advanced in its sanitation dur-
ing the last twenty years ; how much
care had been bestowed by Officers of
Health, not only in benefiting the poorer
portions of London, by turning out the
poor people and letting in light and air,
but also in improving the health of Lon-
don generally. There was scarcely a
person, whatever might be his position
in life, who had not benefited by what
had been effected in that respect. He
agreed with the author in his general
conclusions, and was ready to admit that
he had done a great service in opening
out so important a question.

Mr. W. Atkinson said it appeared to
him that the whole force of the paper
depended upon the question whether
zymotic diseases were the result of the
growth of living germs in the human
frame. The author admitted that water,
if it contained dead organic matter, in
passing down a stream was purified, and
lie assumed, what Mr. Atkinson believed
had never been proved, that zymotic
diseases were dependent upon living or-
ganisms of such great vitality that they
were almost indestructible. He knew
that Professor Tyndall and Mr. Hogg
were high authorities on the subject, but
he did not know that there was anything
to contradict the statement of Dr. Tidy
that there was as yet no absolute evi-
dence of living germs propagating those
specific diseases. The question of chem-
ical analysis, he thought, had been pretty
well cleared up. The author had stated
that although chemical analyses did de-
monstrate the presence of organic im-
purity, yet it did not enable a decision
to be made as to whether it rendered
the water unwholesome. That had been
fully borne out in a little work by Mr.
W. Noel Hartley, Demonstrator of Chem-
istry at King's College, who stated at

DISCUSSION ON THE ANALYSIS OF POTABLE WATKK.

239

page 23: "Even in very nnwbolesome
waters the amounts of organic matter
are exceedingly small. The chemist can
tell how much carbon and how much
nitrogen this organic matter consists of,
but he is powerless to say, by applying
any distinctive test, that he is acquainted
with the nature of the organic matter,
and that it is such as will act as fever
poison ot as cholera poison."

Mr. Chablks Ektn said that, at a recent
discussion at the Chemical Society on
thai question, Professor Huxley pro-
nounced an emphatic opinion that water
might be as pure as possible from a
chemist's point of view, and yet be most
deadly ; but he did not undertake to say
as a physiologist that it was possible to
detect the organisms or organic matter
contained in it. Mr. Ekin quite agreed
with the author and Dr. Thudichum as
to the little value to be attached to the
determination of organic matter in water,
because he had, over and over again, ex-
amined water that had undoubtedly
given rise to typhoid fever, and found
that it contained a very small amount of
organic matter, and he had gone into
districts where there could be no sort of
contamination, and examined the springs,
rivers, and brooks, in which he had fre-
quently found large amounts of organic
matter, that by no test could be distin-
guished from the organic matter in sew-
age. It was well to keep in view the fact
that contamination was simply a question
of degree. Dr. Thudichum would always
go to springs, but he hardly realized the
difficulty of getting pure spring-water
and keeping it pure. Towns that were
using springs for their supply were get-
ting more and more alive to the necessity
of buying land around the springs, to
prevent the water from being contamin-
ated by high y-manured fields or market
gardens. Nearly all the water used for
drinking purposes in England must be
more or less contaminated, because it
was collected on surfaces highly culti-
vated and thickly populated. With re-
gard to the question of previous sewage
contamination, the author overstated the
case when he said is was impossible to
tell whether the nitric acid and ammonia
present in any water had been derived
from rain-water or from the soil through
which the water had percolated. As a
matter of fact it was easy to distinguish

between the two, as the amount in rain-
water did not exceed a certain very small
percentage, and deducting this, the quan-
tity derived from the soil was arrived at.
Although the term " previous sewage
contamination " was in some respects a
misleading one, still there could be no
doubt that the determination of the items
included under this head afforded useful
data in judging of the wholesomeness of
drinking water.

Mr. Folkakd in reply said, on the two
questions of the insufficiency of the pres-
ent methods of chemical analysis, and the
danger of using water which had been
once polluted, he proposed making a few
remarks. With regard to water analysis,
the statement which provoked so much
controversy, that chemists were power-
less to discriminate between wholesome
and unwholesome water, he would quote
from Memorandum No. 3, on Drinking
Water, issued by the Bivers Pollution
Commission: — " The existence of an in-
fectious property in water cannot be
proved by chemical analysis." If chem-
ists could not tell whether a given water
was possessed of infectious power or not,
he thought it was fair to say they could
not tell whether it was wholesome or
not, and therefore the statement in the
paper was corroborated by the opinion
of Dr. Frankland. Again, he agreed
with the opinion frequently expressed by
engineers, that a chemist should be able
to give a decisive report on a sample
from the results of his analysis alone, ir-
respective of the origin of the sample.
If a mineral was submitted for analysis,
the chemist or assayer was indifferent as
to where it came from or what depth it
was obtained. He could report with
certainty on the percentage of iron or
copper, as the case might be, and if the
processes of water analysis were reliable
like those of inorganic analysis, water
analysts could report with equal certainty
whether a given sample was wholesome
or not from the results obtained, irre-
spective of its locality or source.
Whether water analysts were willing to
give a report when thus left in the dark
he left to engineers to decide. He knew
that in at least one case this was not so,
and that gentleman had had considerable
experience, as he had it on good author-
ity that several thousands of samples had
passed through his hands. This seemed

240

VAN NOSTRAND'S ENGINEERING MAGAZINE.

to show that neither Dr. Frankland, nor
any other experienced water analysts,
placed absolute reliance on the results of
chemical analysis to show whether a
water was wholesome or not, and conse-
quently they agreed so far with the opin-
ion expressed in the paper. It was con-
tended that the great question was,
" What is the condition of the water now ?
not what was its condition fifty years
ago, or 50 miles up-stream." This was
perfectly true, but unfortunately it was a
question which no water analyst could
answer. The various processes of water
analysis had one and all been shown on
chemical grounds to be worthless, arid he
had endeavored to prove that they were
worthless (as far as the power of indicat-
ing wholesomeness was concerned) by
reasoning which required no technical
knowledge to follow it, but simply the ex-
ercise of common sense. Eminent water
analysts had brought forward apparently
conclusive evidence of the worthlessness
of all processes of water analysis except
their own, and he was convinced that
each one of those chemists was right,
and begged to refer to their communica-
tions on the subject for proofs of worth-
lessness on chemical grounds. Further,
he believed that the cause of the want of
confidence of engineers in the results of
water analysis was due to the unavoid-
able employment of defective processes,
in the absence of better and reliable ones.
That this want of confidence existed he
knew, because many of his friends were
engineers connected with water-supply,
and he ventured to think many could
from their own experience corroborate
the views at which he had arrived on
theoretical grounds. If this were so,
the sooner analysts owned it the better,
instead of attempting to throw dust in
people's eyes, and to bolster up defective
methods by saying they had employed
them so many thousand times. Consider
the method of ascertaining the present
condition of a sample of water by the
permanganate of potash process. A
measured quantity of water was put in a
glass standing on a sheet of white paper,
and it was noted how many drops of
permanganate of potash were required
to communicate a permanent pink color
to the water. To give it its due, the pro-
cess certainly had the advantage of sim-
plicity, and after performing the experi-

ment some three hundred or four hundred
times it might be a matter of question
whether further repetition would greatly
add to the operator's skill in water
analysis. The sooner the water becamo
pink, the less the amount of foreign
matters present ; but as to the nature of
these substances every one was in the
dark, and when it was inquired if Dr.
Letheby, who invented the process, or
Dr. Tidy, who used it, had established
any definite relation between whole-
someness and permanganate, there was
no answer. An intelligent lad could
master the details of the process in half
an hour, while, as before mentioned, the
value of the result was admitted by nine -
tenths of the analysts of the present day
to be nil. He thanked Mr. Ekin for
supplying an omission in the paper at
page 6, line 15. After the words " by
the rain in falling " it should have been
mentioned that the amount of nitrogen
existing as ammonia and nitric acid in
rain being very small, anything in excess
of the normal amount might, as stated
by Mr. Ekin, be fairly put down to
animal or vegetable contamination. He
could not agree with Mr. Homersham's
remarks on hard water. The quantities
were so small that it could make
but little difference for dietetic pur-
poses whether there were 5 grains or
40 grains of chalk per gallon. Besides
many medical men were of opinion that
lime in drinking water was essential to
the health, at all events, of children, and
therefore he could not but think it un-
fortunate that Dr. Frankland should re-
turn such harmless inorganic substances
as chalk under the heading of impurities.
Although perfectly correct from the
chemist's point of view, it was liable to
mislead the non-scientific portion of the
community. The second question was
as to the purification of rivers by natural
means. Of course a great deal took
place in this way, otherwise (as had been
remarked) no one would be alive.
Vegetation had ' a most beneficial influ-
ence, although he ventured to think that
in nine months of the year in this dull
climate the effects- could not be very
energetic. It must also be remembered
that vegetation was supported by inor-
ganic materials, and that the organic mat-
ters contained in sewage must decay and
be resolved into the salts of ammonia..

DISCUSSION ON THE ANALYSIS OF POTABLE WATKK.

241

carbonic and nitric acids, before they be-
come available for the support of plant

life. All this of course took time. The
statement made by Dr. Tidy, however,
so extraordinary that it would well
repay a little attention. It was to the
effect that 10-miles flow was enough for
purification (whatever that might mean).
The velocity of the river might be as-
sumed to be 2 ' miles per hour, whence
it followed, according to this theory, that
in four hours purification had taken
place. If Dr. Tidy meant that river beds
slmwed no signs of sewage 10 miles be-
low the outfall, the statement was prob-
ably true, but even that would depend on
the ratio of the volume of sewage to the
total flow of the river. But? the assertion
that sewage was decomposed in four or
six hours was rather startling. Even
admitting this would be the case in the
height of summer, during sunshine, and
when vegetation was most active (and
very few if any chemical actions, especi-
ally in dilute solutions, were complete in
such a short time), what should be said
about the winter months when sunshine
was almost an event, and the tempera-
ture of the water was near the freezing
point, the processes of vegetation and
fermentation being nearly suspended? To
say nothing of the fifteen hours' darkness
of the winter night during which no
purification by the aid of vegetation
went on (light being essential), and in
which time the sewage would flow with
the stream 30, 40, or 50 miles. He sub-
mitted that the 10-mile estimate was far
wilder and more fanciful than any asser-
tions in the joaper, in addition to which
it was entirely at variance with facts.
The Rivers Pollution Commission Re-
port contained two analyses of the water
of the Thames, viz., at Reading and at
Shiplake paper-mill, and the result
showed that after a flow of 4 miles the
organic carbon in the water was only re-
duced to about 6 per cent.; and even as-
suming that the diminution went on in
the same ratio, a flow of at least 64 miles
would be required in summer to effect
decomposition, the date of the experi-
ment being May 31st, 1873. As a matter
of fact, however, such processes were al-
most invariably more and more sluggish
towards the close, in addition to which
there was absolutely no evidence to
show that the morbific matters (he was
Vol. XXVIL— No. 3—17.

half afraid to call them germs) were
acted upon in the slightest degree.
The above experiments should be pretty
conclusive to Dr. Tidy, because the or-
ganic carbon was the constituent which
agreed so very closely with some of his
numerous determinations, and the cor-
respondence of which with his own
method he put forward as almost con-
clusive evidence of the reliability of both
processes. After the severe remarks
about germs, it was a comfort to him to
reflect that he was not the only person
who believed in their existence. To his
mind the evidence was as conclusive as
of the presence of calcium, sodium, iron,
&c, in the sun's atmosphere, and in both
cases amounted to far more than a prob-
ability. To some minds, however, the
fact of their not having been seen was to
to the possibility of their existence, but
it should at least be recognized that sev-
eral eminent men believed in them.
The town referred to in the paper in
which an outbreak of enteric fever oc-
curred about three years ago was Cater -
ham. Dr. Thorne Thorne investigated
the matter, and made a full report on the
subject. The evidence was direct and
conclusive that water contaminated with
the dejecta of a workman suffering from
enteric fever was the cause. An epi-
demic of typhoid occurred in the village
of Lausen, near Basle, Switzerland. The
case was investigated by Dr. Hiigler,
and experiments were made similar to
those mentioned by Mr. Baldwin Lath-
am, viz., by throwing about a ton of salt
into the water of the stream opposite the
cottage in which the first attack of ty-
phoid occurred. In two or three hours'
time the water at the village became per-
ceptibly salt, and this was corroborated
by the proper test. Some 20 to 30 cwt.
of flour were then thrown into the brook,
to ascertain if the water was subjected
to any filtering process. None of the
flour (although well mixed up with the
water) arrived at Lausen, conclusively
proving that filtration, which was effect-
ive in stopping such comparatively coarse
particles as those of flour, allowed the
specific poison of typhoid to pass in suf-
ficient quantity to strike down 17 per
cent, of the population with the disease.
A more detailed description had been
given in the Proceedings of the Chemical
Society, February 17th, 1876. It had

242

VAN NOSTRANDS ENGINEERING MAGAZINE.

been urged that the outbreak of fever at
Caterham would not have occurred if the
contaminated water had flowed in con-
tact with the air as a river or brook in-
stead of in closed pipes. Of course this
was possible, but it was a mere assump-
tion, unsupported by evidence ; fortu-
nately for sanitarians and the public the
Lausen case just described set the matter
at rest, a mountain stream then being
the vehicle of the typhoid poison. After
this it would hardly be advisable to rely
on germs being destroyed in flowing
water. With reference to Mr. Baldwin
Latham's remarks on the death-rate of
London having slightly decreased, while
the impurities in the river water had in-
creased in quantity, it must be remem-
bered that the sewerage system and the
sanitary condition of the houses had
undergone vast improvements, and there-
fore to his mind it was exceedingly dis-
appointing that a far greater diminution
in the death-rate had not been observed.
The late Dr. Letheby pointed out that
the real death-rate of London was prob-
ably very different from that shown by
the Registrar General, th£ population
being continually recruited by young
people from the country ; also the sick
were, in as many cases as possible, re-
moved into the country, and of course
many thus died away from home.
These causes probably made a difference
of at least 5 per 1,000, if not considerably
more, and therefore there was no reason
to boast of the corrected death-rate of
the best sewered city in the world. The
statistics of the cholera epidemic of 1854
conlusively showed the ill effects of a
foul water-supply, the relative mortalities
being as 13 to 4. The fact of the death-
rate of the districts of the metropolis,
supplied with river water, being the same
as that of the Kent Company's district,
was doubtless due to the greater number
of recruits from the country who settled
in the former area. If London were in-
creasing eastward as rapidly as west-
ward the cases would be parallel, and Dr.
Tidy's conclusions would hold good, but
in view of this great disturbing element
(the influx of young people from the
country into the western or river-water
districts), such comparisons were almost
valueless, merely showing that even with
.such great advantages the river-water
area death-rate was not lower than that

of the well-water area. He could not
admit that the question of storm over-
flows was irrelevant. It was immaterial
to the inhabitants of the lower towns on
a river whether these overflows were
theoretically necessary or not. The
question to them was " did the sewage
now direct to the river in times of heavy
rain ? " In connection with this subject
it should not be forgotten that the sew-
age thus discharged direct was in its
foulest state, the great rush of water
flushing the sewers and bringing with it
accumulations of filth which had been
collecting and festering, possibly for
weeks. It would be a question of ex-
pense, viz., the construction of sewers in
the upper towns large enough to carry
off storm water without the necessity of
using storm overflows ve?*sus the obtain-
ing of the water supply of the lower
towns from other sources than the river.
There could be no doubt that the upper
towns would feel it a great hardship to
be obliged to spend two or three times
as much on their sewerage system from
this cause, and in view of the partial and
imperfect nature of the remedy this extra
outlay would not be justified. He must
also dissent from Mr. Latham's inference
that low death-rates were the accompani-
ments of offensive states of rivers. It
was probably a mere coincidence and
could hardly be taken as proof of the
harmlessness of such an abnormal state
of things. The fact of malaria usually
traveling up stream was irrelevant. It
was prevalent in almost uninhabited
countries, and was due to conditions of
heat and drought simultaneously present
in the upper and lower parts of a river.
With reference to the effect of water
containing the evacuations of cholera
patients on the inhabitants of Birming-
ham, he did not think it was fair to
expect an explanation of every case.
That injurious effects had followed the
use of such water (putting sentiment
aside altogether) had been proved in
England and on the Continent. It
seemed to him that when an admittedly
polluted stream was to be used as a
source of water-supply the onus of proof
of its innocuousness rested on those who
proposed it. It was not enough to show
that no ill effects had been observed in
particular instances. On the contrary,
he thought two or three undoubted

DISCUSSION ON THE ANALYSIS OF POTABLE WATER.

243

cases, of the transmission of disease by
such waters, should be enough to con-
demn them as a class, and prevent
wherever possible their use for domes-
tic purposes. Besides, the mere idea
was so loathsome that one almost won-
dered that an attempt should be made to
defend it. If " drinking in a circle "
were unobjectionable, then why have
such refinements as sanitary inspectors,
inspectors of nuisances, and food ana-
lysts ? It certainly seemed inconsistent.
The question had been put to him " ad-
mitting the presence of germs, was
there any evidence to show that they
were not amenable to the same laws as
organic matter generally ? " Here the
necessity of extreme precision would be
seen. The term organic matter was in-
definite. If living organic matter were
meant the answer would be self-evident,
because germs were living organic
matter, and therefore must be amen-
able to the laws governing such matter.
If, on the other hand, his interrogator
meant dead organic matter, he replied
that germs were no more amenable to
the laws of dead organic matter than a
living man was. Again, every biologist
was aware that the lower the organism
the more persistent was its vitality, as a
rule, and therefore a living germ was at
the very least quite as capable of resist-
ing oxidation during a 10 or 100, or
1,000 miles swim down a river (water
being its appropriate medium) as was a
hen's egg for an equal time or during
transport through an equal distance in
its appropriate medium, the atmosphere ;
and he thought few people would doubt
the capacity of a hen's egg to germinate
after such an interval and such treat-
ment. Under the circumstances he could
leave the members of the Institution to
decide which of two chemists was the
more likely to gain respect, the one who,
after ten years' experience in water an-
alysis, had come to the conclusion that
the present methods were unreliable,
and was willing to own it; or on the
other hand, the one who tried to throw
a halo of importance round a process ad-
mitted by nine-tenths of the analysts of
the present day to be worthless, by stat-
ing that he had analyzed nearly four
thousand samples by it. It would be
equally logical to say that ha aging for
sheep stealing was a good law because it

had (unfortunately) been carried out
hundreds of times in this country. In
conclusion he must thank the members
for the kind way in which they had list-
ened to the paper and to his remarks,
and if it should be the means of direct-
ing still further attention to this im-
portant subject he should be extremely
gratified.

CORRESPONDENCE.

Mr. H. Percy Boulnois said that the
Water Works of the City of Exeter, of
which he had charge, were the property
of the Corporation. The daily supply
amounting to 1,280,000 gallons, was
pumped from the river Exe, the intake
being situated about 4 miles above Exe-
ter and 12 miles below the town of Tiv-
erton, the sewage of some ten thousand
persons at this place being daily passed
direct into the river in a crude state.

To ascertain how far this sewage con-
tamination chemically affected the water,
he took samples from different points in
the river in August, 1880, and submitted
them to Mr. F. P. Perkins, the public
analyst of the City of Exeter, who exam-
ined them by the permanganate process
and a modification of Professor Ditt-
mar's carbon process. The following
Table (see next page) embobied the re-
sults of these tests.

It would be noted, on reference to this
Table, that the water at the intake was
chemically nearly similar to that above
Tiverton, and that this result was ob-
tained gradually by the water on its
journey. The Dart stream, however,
seemed to pollute the water, there being
a marked difference between samples 4
and 6 ; this was accounted for by the
fact that the Dart rose on Exmoor, and
although it could receive absolutely no
sewage contamination, it was brown with
peat, and this gave a bad analysis.

So far as Exeter was concerned, it was
contended that the water at the intake
was not unhealthily affected by the sew-
awe contamination of Tiverton, and this
result might be attributed to the follow-
ing causes : (1) The excessive dilution
of the sewage with a large bulk of pure
water. (2) The oxidation which the
water underwent on its 12 miles journey
from Tiverton, tumbling as it did over
two weirs and rushing over many a shal-
low and stony bed. (3) The action upon

244

VAN ISTOSTKAND'S ENGINEERING MAGAZINE.

SPECIMENS OF WATER TAKEN BY MR. BOULNOIS FROM THE RIVER EXE ON
AUGUST 16TH, 1880, AND SUBMITTED TO MR. PERKINS FOR ANALYSIS.

Number

of
specimen .

Where obtained.

Above Tiverton

Below Tiverton

Ditto

Bickleigh Bridge

j In a stream joining the )
{ Exe called the Dart. . . )

Below Bickleigh mill stream.

Bourne Farm

Thornetown above the weir. .

At intake '

Distance below
Tiverton.

1 mile above . . .
100 yards below

2 miles

3 "

3i "

5 "

8 "

12 "

Amount of organic im-
purity in 100,000 parts.

Oxygen con-
c

sumed x -==
o

.0718x2.27:
.0873x2.81:
.0929x2.93:
.0788x2.41:

.2070x2.11:

.0859x3.16:
.080 x2.70:
.0831x2.60:
.0715x2.29:

Organic

carbon

yielded.

.163
.246
.273
.190

.436

.272
.218
.218
.164

the water by aquatic plants and weeds,
and of the soil of the river banks and
bed. (4) The constant evaporation from
the surface of the water, and consequent
molecular changes thus altering its char-
acter. (5) Other unknown causes possi-
bly at work which made up the ever act-
ive processes of Nature's great labora-
tory.

The author questioned the reliability
of chemical analysis to detect " previous
sewage contamination, " but he did not
appear to have given credit to the fact
that, in a properly conducted analysis,
no chemist relied upon one indication
only, but that all the bearings of the
analysis and history of the water were
considered. If the analysts' evidence
was to be doubted, much difficulty would
be experienced by sanitary authorities in
closing polluted wells or other impure
sources of water supply; but hitherto
reliance had always been placed upon
such evidence, and he thought no suffi-
cient proof had been adduced in the
paper to shake public confidence. The
question was one of grave importance,
the health of a community being no
doubt greatly affected by the character
of its water supply ; no hasty conclusion
should therefore be arrived at in favor
of deep well water. It might be that
the terrible " diseases of the stomach
and intestines " mentioned in the paper
were due to contaminations in shallow
well waters, or to the mineral substances
found in most deep well waters, and not
from that source which Nature pointed

out as the most convenient and proper
from which to derive the water supply.

Mr. Edwin Chadwick, C.B., observed
that there were particles from small-pox
and other eruptive diseases, which were
known to be distributed in hospitals
within measurable distances. But these
were imagined, but not proved, to be
germs of specific diseases which spread
,to immeasurable distances, and which it
was averred must be productive of the
same diseases. These germs were al-
leged to be the cause of enteric fever,
and when conveyed by water carriage
must generate it. A disease did arise
sometimes, with varying type, from the
emanations from stagnant drains or sew-
ers. But he never heard of any arising
in such conditions along lines of sewer
in accordance with the germ theory.
In an address given at Croydon to the
members of the International Medical
Congress by Dr. Alfred Carpenter, ad-
ducing experiences in answer to the vio-
lent objections that had been made by
the advocates of chemical disinfectants,
and other processes against sewage
farms, on the grounds that they must
receive and must spread the germs of
infectious disease. Dr. Carpenter stated
the result of his experience, to which
he would direct particular attention : it
was as follows :

" The non-infectious character of the excre-
tions of those suffering from epidemic and in-
fectious diseases when distributed upon a sew-
age farm is proved by the fact that there have
been occasional outbreaks of infectious diseases

DISCUSSION ON THE ANALYSIS OF POTABLE WATER.

245

in Croydon during the past ten years, includ-
ing twb epidemics of small-pox, several out-
breaks of scarlet fever, occasional cases of
diphtheria, and three periods of typhoid prev-
alence— two of wbich were distinctly con-
nected with contamination of water supply in
its distribution, and a third was distributed by
means of milk. In the years 1875-76 the ex-
creta of at least a ttiousand cases of enteric
fever were utilized on the farm. In the ma-
jority of the cases the excreta were certainly
not disinfected, and had they been capable of
setting up the disease, some of the sixty-five
persons at that time in the employ of
the Local Board must have suffered from
the infection. Cases which did arise were
not on the farm, or even in the major-
ity of cases, near to it; they were on the
hills, beyond the range even of subsoil water.
The changes in sewage are not in any way
similar to those which have been known to
take place in poudrette and other particular
forms of dried ordure. There is no doubt in
my mind of the destruction upon sewage
farms of the germs of mischief, which, when
unaltered, may be capable of setting up zymo-
tic disease They are not preserved as they
may be in dried ordure, or in other products in
which so-called disinfectants have been used,
which have simply preserved the germs from
decay; but they are chemically and physically
altered so that mischief cannot arise. This re-
sult has been also found to apply to the excreta
of animals suffering from epizotic disease.
During the past few years there have been
several outbreaks of infectious pleuro-pneu-
monia in the Croydon district, the infection
being brought from the Metropolitan Meat
Markets. The cow-sheds in which the disease
has arisen have drained into the Croydon sew-
ers, and blood and excreta from the slaugh-
tered animals have been washed down those
sewers. The sewers have carried the morbid
matter from the sheds to the farm; but there
has been no corresponding disease among the
cattle upon the farm."

To this he might add that similar dem-
onstrations were presented by all well
worked sewage farms. Moreover, in-
sects generated and distributed in solid
manures, and in stagnant semi-liquefied
manures, were drowned by liquid man-
ures in active circulation. It must fol-
low that from continued exposure to
such germs as those assumed that the
health of those working on the sewage
farms must be lower than the average,
whereas it has been shown in a report to
the Royal Agricultural Society that the
health of the people working and living
on the sewage farms was remarkably
higher than the average.

Mr. C. E. De Rance remarked that the
author, by grouping a series of well-
known facts in a definite connection, had
done useful work, in establishing the un-

assailable result, that the practical free-
dom of drinking water from organic im-
purity must be absolute to prevent the
spread of zymotic disease. How this
desirable condition was to be obtained
was a difficult problem. Gravitation
supplies, derived even from the mount-
ain slopes of Wales and the English
Lake District, traversed only by mount-
ain sheep, occasional tourists, shepherds
and their dogs, were liable to receive
the germs of entozoa, especially from the
latter ; while water supplies abstracted
from rivers, even when all town sewer-
age was intercepted, received streams
flowing past polluted farm yards, and
the soakage from the offensive ditches
with choked outlets, which so often sur-
rounded them. In a gravitation supply
absolute freedom must of necessity be
impossible, but much could be effected,
by making the separation of sewerage
and storm water compulsory, not only
in the drainage from cities and towns,
but in the effluent water from country
estates.

In water obtained from underground
sources, whether from deep - seated
springs, or wells, the chances of poison-
ous germs being left was very small,
after the passage of the water through
several hundred feet of porous rocks,
provided that the water had passed
through the texture of the rock, but in
many cases, the water had simply trav-
eled, both vertically and horizontally,
through open fissures formed by joints
and faults, and this was probably the
condition of many wells giving an ex-
ceptionally large daily yield of water,
which had not been naturally filtered.
In some other cases, deep bore holes
had been sunk entirely in porous rock,
in which every care was taken to ex-
clude, and tube out, surface waters, but
the water yielded was found to be pol-
luted, percolation having taken place
through cracks and fissures, connecting
the surface with the saturated portion of
the rock beneath. Of necessity wells
reaching porous formations after passing
through a zone of impermeable material
were not open to this objection, and the
chances of pollution were exceedingly
small in the water yielded by them and
by deep-seated springs. To increase the
yield of these springs appeared to be a
matter of the highest importance, for

246

VA1ST nostkand's engineebing magazine.

should the construction of " dumb
wells " become general, and the drainage
of impermeable lands be artificially car-
ried to porous strata beneath, whenever
practicable, the supply of pure drinking
water would not only be increased, but
the absorption of excessive rainfalls would
diminish the intensity of floods, and im-
prove the dry-weather volume of the
streams.

Mr. H. U. McKie knew one town in
Wales which took its water supply from
a river, when about one mile of extra
piping would have given good spring
water. Villagers near the river from
which the water was taken would not
use it, yet chemists pronounced it pure.
He had recently had occasion to exam-
ine some works by a river side, and saw
what he thought to be two sticks float-
ing down the rippled surface of the
stream ; they appeared to be attached to-
gether by a string, and made curious
bobbing motions, similar to a float on a
fishing-rod when there was a nibble at
the bait ; on closer examination he found
it was a large salmon so covered with a
fungoid growth as to be both pitiable
and revolting, and he was told that the
river was full of salmon thus affected.
Now, as this disease also attacked trout,
ells, and other fish, in the river, he
thought it right to ask if water so con-
taminated could be a safe source of pot-
able water supply for a town ? He knew
of two towns on this river which derived
their water supply from it, and there
might be others.

Mr. H. Robinson could not agree with
the author in his sweeping condemna-
tion of the use of river water unless
taken near the source. However desir-
able it might be to obtain water free
from the risk of contamination (and
every engineer aimed at securing such a
supply) in practice it would be impossi-
ble to meet the wants of the community;
if the rule laid down were acted on. The
enforcement of this rule would necessi-
tate the abandonment of numerous
sources of supply which failed to comply
with these conditions, but which, al-
though subject to the risks referred to,
had not produced any evil results. Prob-
ably the author, by enforcing an unrea-
sonably high standard of purity, would
create some of the evils which it was
sought to prevent. If only water from

deep subterranean sources or from
streams above suspicion of contamina-
tion were to be used, a less abundant
supply would be available than was now
employed. The limitation of supply
would arise from two causes, one being
the difficulty of obtaining the necessary
quantity of underground water, and the
other being the cost of getting it.
Where the cost of supplying a town was
attended with heavy water rates, Mr.
Bobinson had found that the authorities
were disposed to restrict the quantity
used for sanitary purposes, such as flush-
ing sewers, road watering, and the like.
Such restriction would lead to insani-
tary results. The alarmist views enter-
tained by the author were not supported
by practical evidence. If the germs of
contagious diseases had the vitality and
produced the mischief alleged, the evils
attending the use of water subject to
their influence would have been mani-
fested. Without wishing to underesti-
mate the risk of transmitting diseases by
water, Mr. Robinson would expect to
find some proof of the allegation in the
case of a city like London. Obviously
the water supplied by the metropolitan
companies which took their supply from
the Thames must be placed in the class
of water of the dangerous kind ; no con-
tagious diseases, however, could be
traced to its use. Frequent attempts had
been made to connect cases of typhoid
and similar diseases to the use of water
supplied from the Thames, and he had
on several occasions been engaged in ex-
amining into such cases. He had found
(and the experience of others was to the
same effect) that where water had caused
illness it had been solely through the
foul state of the cisterns and receptacles
for storing it. The presence of filth of
various kinds and dead animals ac-
counted for the mischief. A constant
supply, would remove this cause of dan-
ger.

Another view of the subject was worth
referring to. Supposing water perfectly
free from suspicion was to be insisted
on for dietetic purposes, a duplicate sup-
ply would be required in many cases,
such as has been proposed for London.
Were this system to be adopted the in-
ferior water would most probably be less
pure than that previously supplied, inas-
much as it would be thought unneces-

EXPERIMENTS IN THE TRANSMISSION OF POWER BY ELECTRICITY. 247

sury to filter water intended to extin-
guish fires, water streets, or cleanse
courts, and alloys. The germs of some
contagious diseases wore, according to
the host medical authorities, even more
capable of being introduced into the
human system through the lungs than
through the stomach. If, therefore, the
dangers apprehended were really based
upon reasonable grounds, the air in-
stead of the water might become the me-
dium for conveying the disease germs
under the state of things that would
then exist. Much inconvenience had

been experienced by engineers, owing to
analytical chemists adopting different
terms to express the results of their an-
alyses. Mr. Robinson was continually
having to deal with analyses in which
similar impurities were described by dif-
ferent chemists in different terms. The
adoption of a uniform nomenclature
would be both convenient to those who
had to act upon the results of chemical
analyses, and would also remove one of
the several grounds of difference that
appeared to exist amongst chemists
themselves.

SOME EXPERIMENTS IN THE TRANSMISSION OF POWER

BY ELECTRICITY.*

By GEORGE and WILLIAM E. GIBBS.

Contributed to Van Nostrand's Engineering Magazine.

DESCRIPTION OF GENERATOR AND MOTOR.

The dynamo-electric machine used as
a generator was one of Mr. Weston's
latest pattern, known as the " fifty light
incandescent machine." The machine
used as a motor was identical with the
preceding, except that it was only in-
tended to run forty lights.

The machines were of the derived field
type, that is, the field magnets were
wound with comparatively fine wire, so
that their resistance was about 800 times
the resistance of the armature. The
terminals of the field wire were connected
with the brushes directly, and there
fore when the machine was running the
magnets became charged even if the
main circuit was not closed.

In this machine the magnets are hori-
zontally arranged above and below the
armature. They are essentially two
horse-shoe magnets with like poles
turned toward each other. The arma-
ture is wound with a continuous heavy
wire which is brought out at every turn
into a loop and soldered to the commu-
tator.

The core of the armature is made up
of thin wrought iron discs separated
by small washers of gelatinized fiber.
The discs are shaped somewhat like a
gear wheel, that is, they have teeth on

* Abstract of a Tbesis written at the Stevens Insti-
tute of Technology.

the edge to the number of perhaps
twenty and of the width of one-fourth
of an inch, so that when the armature
is complete there are a number of ridges
running its whole length parallel to the
axis. In the hollows between the
ridges is wound the wire of the arma-
ture in a single layer, which, when fin-
ished, is of the same height as the
ridges, making the whole a true cylin-
der. The ridges are called " polar ex-
tensions," for by projecting through the
layer of wire they come very near to the
field magnets and increase the polarity
of the armature when the machine is
running, and consequently the intensity
of the lines of magnetic force. The
core is, moreover, pierced from end to
end with several holes arranged at equal
angular distances apart, and the discs
of which it is made up being separated
from each other by the space of about a
twentieth of an inch, a complete system
of ventilation is kept up by the action
of the machine, and the armature is thus
kept cool. Each disc has also two
radial slots cut in it to prevent the for-
mation of an extra currrent. The com-
mutator is composed of copper sectors
separated by gelatinized fiber strips.

The brushes are of silver plated cop-
per, each brush being composed of
several ships, placed on one another,
so that although the brush has great
flexibility it has also sufficient springi-

248

VA2? XOSTRAXD' S EXGEN'EEEEN'G ^XAG^ZES'E.

ness to cause it to press uniformly on
the commutator.

Each brush is, besides, held in a spring
clamp, which yields to any inequality of
the commutator. The brushes are ad-
justable at any angle about their axis,
and are in practice turned to the point of
least sparking, which is the neutral plane
of the machine. When properly ad-
justed the sparking is inappreciable.

The wire from each pair of field mag-
nets terminates at a binding post on the
top of the machine. When the genera-
tor is working to its full capacity these
posts are connected by a short wire, but
when it is desirable to use only part of
the power of the machine, a variable re-
sistance is placed between them. By
altering this resistance the intensity of
the magnetic field is varied, and the
work done may be perfectly controlled.
The resistance of the armature was .03
ohms, and the resistance of the field
was 24.5 ohms, measured while warm,
immediately after the exj)eriments
ceased.

DESCRIPTION OF DYNAMOMETER.

In measuring the power transmitted
from the engine to the generator, the
Kent dynamometer built by the class of
'76 of the Stevens Institute was used.
In this dynamometer the receiving and
transmitting pulleys are each carried by
a separate shaft. These shafts are in
the same straight line, and upon the
ends which face each other there are two
bevel wheels. A third bevel wheel at
right angles to these two connects them
and transmits motion from one shaft to
the other. This wheel is loose upon its
axis, which is prolonged to form a pen-
dulum, and is supported by a brass
pic passing through it and fitting into
holes in the transmitting and receiving
shafts. A heavy weight is attached to
the end of the pendulum, and when the
machine is running the pendulum is de-
flected from the normal vertical position
to a position approaching more or less
the horizontal.

The sine of the angle of deflection,
the weight of the pendulum and "bob,"
and the number of revolutions per min-
ute determine the power transmitted.

The dynamometer was standardized as
follows :

The pendulum was supported in a

horizontal position by a prop at a dis-
tance of two feet from the center of the
pin connecting the shafts. The lower
end of the prop rested on a platform scale.

The weight indicated was 170.5 lbs.,
and since the lever arm of this weight
is divided by two. by the arrangement of
gear wheels above described, the weight
at one foot is 170.5 pounds.

Then to get the power transmitted
we have,

W = 170.5 X sine 6 X (6.28 = 2;r)X
number of revolutions.

Where W = work done in ft. lbs. per
min.

Of this power, however, a certain per-
centage is lost in overcoming the friction
of the bearings and must be allowed for.

To find the friction, the main ' and
field circuits of the generator were
broken but the brashes left on the ma-
chine. A seven-inch pulley was fastened
on the shaft of the generator, close to
the twelve-inch driving pulley. On the
small pulley a prony brake was arranged,
so that when the engine was transmitting
power to the generator through the
dynamometer the energy absorbed by
the brake was substituted directly for
the electrical energy developed by the
machine when the circuits were closed.

Several experiments were made at dif-
ferent deflections of the pendulum.

The variation was not great, but the
mean is given.

The speed was constant, and was the
same as in all the experiments on the
efficiency of generator.

Dynamometer :

Sine of deflection =.33.

Weight = 170.5 lbs.

Radius of driving pulley =16 inches.

'1 herefore the constant pressure

170.5x.33

indicated = — — — =42.3 lbs.

l.oo

Prony brake :

Length of arm = 30 inches.

Pressure on scale = 7. 25 lbs.

Pressure at circumference of pulley

Qf)

= 7.25x^ = 36.25 lbs.

Since the dvnamo pulley is 12 in di-
ameter; 42.30-36.25 = 6.05 = loss

by friction, and j^- = 14. 2 per cent

friction.

EXPERIMENTS IN THE TRANSMISSION OF POWER BY ELECTRICITY. 249

FRICTION OF ARMATURE BEARINGS.

Lack of suitable apparatus prevented
us from determining this experimentally,
but since it has been found for similar
machines by repeated experiment to be
less than 3 per cent., and since the bear-
ings in the machine used were as nearly
perfect as skillful workmen and accurate
mechanical ' means could make them
(being a steel shaft running in gun metal
bearings), we felt at liberty to assume
the friction as 2.5 per cent. The bear-
ings were oiled by continuous oilers and
the heating was so small as to be imper-
ceptible even after long runs.

EFFICIENCY OF GENERATOR.

In making tests for the efficiency of
the generator, the current generated was
carried by iron wire resistances running
across the room from side to side in the
open air, so that the heat generated was
rapidly conducted away.

A switch was so arranged that the
generator could be instantly thrown out
of circuit and the resistance of the line
measured within five seconds. In this
way the varying effect of temperature
on the resistance was eliminated.

All resistances were measured by a
Thomson high resistance galvanometer.
An electric lamp placed in a magic lan-
tern threw a ray of light on the galvan-
ometer mirror, which was reflected to a
screen. This gave an immensely magni-
fied motion to the image so that the
scale could be read from some distance
in a well -lighted room.

CALORIMETER TEST.

In determining the electrical energy
developed by this method, a calorimeter
was used in circuit with the iron wire
resistance.

This calorimeter consisted of a cylin-
drical vessel of galvanized iron imbedded
in sawdust in a wooden box. By this
means any great waste of heat by con-
duction and radiation was prevented ;
but as some heat must have been con-
ducted by the wood, it was allowed for
in each case by taking water at the
atmospheric temperature and cooling it
by means of ice to as many degrees
below that temperature as it was to be
raised above it by the heating of the coil.
In this way the transfer of heat from the
sawdust to the water during the first
half of the experiment was equal to the

transfer from the water to the sawdust
during the second half. The electrical
energy expended in the calorimeter was
measured by its heating effect on a coil
of German-silver wire. The wire used
in the coil was of No. 8. B. W. G.

The coil itself was entirely immersed
in the water, and its ends were soldered
to two copper rods which were fastened
in the calorimeter cover. In this way
the high resistance wire being entirely
under water, any over-heating was pre-
vented. The resistance of the coil was ex-
actly .09 ohm at 74° Fahr. in the water.

Distilled water was used in the calorim-
eter, it having a much higher resistance
than ordinary water, thus diminishing
the tendency of the current to pass
through the water from one turn of the
coil to another. No evidence of such an
action having taken place was, however,
observed at the conclusion of the tests.

An uniform temperature of the water
in the calorimeter was secured by using
two miniature screw-propellers of wood
which were constantly turned in the
water during the experiment.

When everything was ready for the
test the generator was run until the cir-
cuit was thoroughly heated, and its
resistance remained constant.

The calorimeter was then thrown into
the circuit and an equal resistance of
circuit thrown out, "so as not to alter the
total resistance. At the end of the test
the resistance was measured as soon as
the circuit was broken and before the
wires had cooled.

DATA FROM THIS TEST.

"Weight of calorimeter empty, 31 pounds.
Weight of calorimeter full, 58.25 pounds.
Weight of water in calorimeter, 27.25

pounds.
Range of temperature, = 91.°2 = 68.°6 =

22.°6 Fahr.
Specific heat for above range, =1.018.
Time of test, =25 minutes.
Resistance of iron wires and calorimeter

coil, =.484 ohm.
This resistance and field in multiple are

= .475 ohm.
Total resistance of circuit, =.475 + .03 =

.505.
Resistance of calorimeter coil, =.09 ohm.
Ratio of resistance of total circuit to

resistance of calorimeter coil, =

•505-™i
Tog— 5-61-

250

VAN NOSTRAND'S ENGINEERING MAGAZINE.

EESULTS.

Energy developed in calorimeter ==

27.21X1.018X22-.6X772=1933089

ft. lbs. per minute.
Total electrical energy developed in cir-
cuit, 19330.89x5.61=108446.28 ft.
lbs. per minute.

Determination of the energy transmit-
ted by the dynamometer in this test :
Speed of dynamometer, =340 revs, per

min.
Sine of the angle of deflection, =.36.
Therefore, indicated energy =

170.5 x .36 x 6.28 X 340=131056.4 ft.

lbs. per min.
Determination of the efficiency of gen-
erator from the above :
Energy consumed in turning armature

in field of force =

131056.4 x. 858 = 112446. ft. lbs. per

min.

™ . 108446.28 ...

.-. Efficiency = ^^ =.963.

That is, 96.3 per cent, of the power
applied to the armature pulley appears
■as electrical energy in circuit and mag-
net coils.

Now, to find the " commercial efficien-
cy,'' or the ratio of the mechanical energy
required to drive the dynamo (including
friction of armature bearings and agita-
tion of air by armature) to the electrical
energy which appears in external circuit,
we have :

Energy actually applied to armature
pulley = total indicated energy less the
friction of the dynamometer =131056.4
X. 883 = 115722.8 ft. lbs. per min. Of the
total electrical energy generated there
appeared in the armature — 108446. 28 X

03
^— = 6442.35 ft. lbs.

And the electrical energy consumed in
the field circuit, which appeared partly
as heat and was partly used in magnet-

errvfr

izing the cores=108446.28X;r7-— T = .02

^4.51

X 108446.28=2168.92 ft. lbs. per min.

Then the total internal work =2168.92
+ 6442.35=8611.27 ft. lbs. per min.

Therefore the amount of energy ap-
pearing in external circuit =108446. 28 —
8611.27=99835.01 ft. lbs. and the com-

. . _ . 99835.01 0/wl

mercial efficiency = n5722 8=.866.

TESTS BY MEASUREMENT OF THE ELECTRO-
MOTIVE FORCE AND RESISTANCE.

In order to determine the electrical
energy by this method, we first meas-
ured the electro -motive force of the ma-
chine and the resistance of the line very
accurately. From these data we found
the current flowing by the formula

c=- . Then, knowing the current, the

electrical energy developed in external
circuit is given by the following empiri-
cal formula— c2Rx 44. 24= energy in ft.
lbs. per min.

The electro-motive force was meas-
ured between the binding posts of the
generator by means of a condenser and
a Thomson high resistance galvanom-
eter.

The standard of electro-motive force
employed was the Latimer Clarke cell.
Two of these cells were obtained newly
made up from the "Western Union Tele-
graph Company. They were allowed to
charge a micro-farad condenser, and the
condenser was then discharged through
the galvanometer. A number of experi-
ments were made with these in order to
determine accurately the deflection on
the scale corresponding to a cell. This
deflection is proportional to the current
flowing through the galvanometer coils,
and, consequently, of the charge held by
the condenser, which depends upon the
electro-motive force of the charging cell.

The deflection corresponding to one
cell was found to be exactly five divisions
of the scale. Elliott Rro.'s switch was
used to connect the dynamo and galvan-
ometer alternately with the condenser.

The connections were made as perfect
as possible by amalganation.

DATA.

Capacity of condenser =.05 micro-
farad. Deflection of galvanometer with
condenser charged by cell =5 divisions.
Average deflection of galvanometer with
condenser charged by dynamo=103.5
divisions. Electro-motive force of cell=
1.457 volts.

Therefore, 5 : 1.457 : : 103.5 : (x =
30.159 volts). Resistance of line while
hot =.431 ohm. Since the electro-motive
force was measured between the bind-
ing-posts, the resistance of the armature
was excluded.

EXPERIMENTS IN THE TRANSMISSION OF POWKR BY ELECTRICITY. 2.")1

Resistance of armature =.03 ohm,
.-. Resistance between binding-posts:
.401 ohm.

30.159

Then-c=:

.401

= 75.2webers.

Energy developed in external circuit =

(;RX 44.24 =
(75 : -2)- x .401x44.24=100330.8 ft. lbs.

per min.

Total electrical energy —
100330.8X-1T^r = 107352.95 ft. lbs. per

401

mm.

Energy indicated by dynamometer —

Sine of mean deflection = .352

Mean speed = 340 revs.

Indicated energy —

170.5X. 352x6.28X340 = 128306 ft. lbs.
per min.

Applied energy (equal total energy
minus combined friction) = 1 28306 X. 868
= 110087 ft. lbs.

Therefore, efficiency of machine =

107352.95 nP7r

— -=.975 or d(.o per cent, act-

ually appeared as electrical energy in ex-
ternal and field circuits.

Determination of the commercial eff.

Energy actually applied to armature
pulley —

128306 X. 883 = 113294.19 ft. lbs. per min.

Of this there appeared in the arma-
ture-
OS
107352.95 X -^- = 7472.35 ft. lbs. per

. 4«jl

min.
And in the field circuit —

107352.95 X

431

24.51

= 1887.76 ft. lbs. per

mm.

Therefore, total internal work =

7472.35 + 1887.76=9360.11 ft. lbs. per
min.

Then there appeared in external cir-
cuit—

107352.95-9360.11 = 97992.84 ft. lbs.

And commercial efficiency =

07992.84

1I32909-864-

The resultant efficiency of the gener-
ator will be the mean of the two efficien-
cies as determined by the two methods,
or;

Average efficiency =.969

Average commercial efficiency =.865.

EFFICIENCY OF MOTOR.

In determining the efficiency of the
motor as a machine for converting elec-
trical energy into mechanical, we con-
nected the generator and motor by heavy
copper rods in order to reduce the loss
of energy in the line to a minimum. A
prony brake was applied to the pulley of
the motor and the pressure of its arm
upon a platform scale measured directly.
This gave an accurate indication of the
power of the motor.

To avoid heating of the brake by fric-
tion, it was arranged in such a manner
that a stream of cold water entered it at
the top, and after passing through it to
the pulley, escaped by a hole in the bot-
tom. In this way we were enabled to
make runs of any length of time. Be-
tween the nuts which tightened the
brake, and the brake itself, were placed
thick rubber washers, which by their
elasticity yielded to any inequality of
motion, and kept the speed and corre-
sponding pressure on the scale very con-
stant.

By means of the brake we could ap-
ply variable loads and get various ratios
between the speeds of the two machines.

The electrical energy entering the
motor was controled by altering the vari-
able resistance in the field of the gener-
ator.

Although this alteration diminished
the intensity of the magnetic field, the
work done in the coils did not vary un-
til after the third decimal place, so the
commercial efficiency of the machine re-
mained constant.

The conditions, however, having been
altered, the results are not such as can
be plotted in a curve.

It is to be remarked, that in these ex-
periments, the machines which we used
were so large that it was not possi-
ble to work them up to their full capac-
ity, the dynamometer being unable to
transmit sufficient power.

252

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

The results obtained are tabulated as
follows :

DYNAMO.

T3
CD

°.2

CD o

P CD

Indicated

power
in ft. lbs.

Per cent,
applied to
armature.

Actual energy
applied to
armature.

Ft. lbs. current

in external

circuit.

405
405

.355
.420

153945.6

.883

135928

.638

86717

182132.8

.883

160820

.638

102603

405
405
405

.475
.515
.565

206983.6

.883

182763

.638

116000

2233295

.883

197200

.638
.638
.638

125813

243060.6

.883

214620

136927

405

.520

225497.8

.883

169910

108402

405

.585

253685.0

.883

223995

.638
.638
.638

142905

405
405

.66

286208.8

.883

254921

152638

.31

134431.4

.883

118701

75730

405

.345

149609.1

.883

132104

.638

84279

405

.350

152777.3

.883

134895

.638

86059

405

.360

156113.9

.883

137847

.638
638

87941

405

.515

223329.5

.883

197200

125823.

MOTOR.

No.

Speed

Wt.

Ft. lbs.
given out
by motor.

Ft. lbs. of
current

in external
circuit.

Effi. of
mortar.

932

29264.8

86717.0

.337

892

56017.6

102603.0

.545

860

81012.0

116000.8 .699

844

106006.4

125813.0 .842

800

125600.0

136927.0 .917

1042

65437.6

108402.0 .603

1021

96178.2

142905.0

.671

1185

74418.0

152638.9

.481

763

47916.4

75730.6

.633

717

67541.4

82279.8

.809

572

71843.2

86059.8

.834

564

70838.4

87941.9

.806

738

115866.0

125823.6

.921

No.

Work done
by motor.

29264.8

56017.6

81012.0

106006.4

125600.0

65437.6

96178.2

74418.0

47916.4

67541.4

71843.2

7083^.4

115866.

Work ab- j Efficiency

sorbed by
generator.

135928

160820

182763

197200

214620

169910

.390

223995

.429

254921

.292

118701

.403

132104

.511

134895

.532

137847

of com-
bination.

.214

.348

.443

.539

.580

,515

197200

.589

EFFICIENCY OF MOTOR.

The motor, as a machine for convert-
ing electrical energy into mechanical,
seems to be excellently adapted to the
purpose. The only point that admits
of improvement is probably the resist-
ance of the magnet coils, which should
be higher in proportion to the resistance
of the armature, thus taking less current
to keep up the magnetic field.

EFFICIENCY OF THE COMBINATION.

It is when the generator and motor
are coupled together that the efficiency
of the whole falls, as is shown by the
tables, to such a low percentage.

The reason for this, however, and the
means of remedying it seem obvious.

By one of the fundamental laws of
electricity, we know that the work done
in any portion of an electric circuit is
directly proportional to its resistance.

In the case of the two machines
coupled, as in the above series of experi-
ments, the resistance of each was very
low and equal, while the resistance of
the line was practically nothing.

Under these conditions, nearly half the
work must necessarily be done in the
generator, and the results verified this
law.

In order then to increase the efficiency
of the combination, more work propor-

THE ROLLING STOCK OF THE ST. GOTHARD RAILWAY.

263

tionally must be done in the motor and
less in the generator. To accomplish
this, we find by applying the above rule
that one of two things may be done, we
may either decrease the resistance of the
generator or increase the resistance of
the motor. In practice, a compromise
would probably be made, that is, the
generator armature would have its
resistance reduced, and the motor have
the resistance of its armature raised suffi-
ciently to cause nearly all the work to be
done in the motor.

This applies to a single motor.

Where several motors were supplied
with current from a single machine they
would probably be arranged in " multiple
arc," and be of such a resistance that
they would take only a certain amount

of current, and, when coupled up with
the generator, their resulting resistance
would be the same as would be given to*
a single motor doing the combined work
of all.

In this way each machine does in a
measure induce its own current and con-
trols the current generated, so that if
only one motor is running, the current
generated is only sufficient for it and as
each one is put in circuit the current in-
creases in a ratio which just keeps each
motor supplied with the proper amount
of current.

When by a course of experiment the
proper ratio of resistances shall have
been determined, there seems to be no
reason why the combined efficiency
should be below eighty per cent.

THE ROLLING STOCK OF THE ST. GOTHARD RAILWAY.

By R. ABT.

From " Organ fiir die Fortschritte des Eisenbahnwesens," for Transactions of the Institution

of Civil Engineers.

Although this railway is to be opened
to traffic this year the rolling stock is
still wanting, and great discussion has
taken place on the question, especially as
to whether the engines are to be tank- or
tender-engines. Whilst the existing
Alpine lines are satisfactorily worked by
tender-engines, the frequency of good
water stations on the St. Gothard, with
other advantages, spoke strongly for the
use of tank-engines. To decide this and
other questions a careful study has been
made of the locomotive working in
Switzerland and other countries.

The total length to be worked by the
engines of the St. Gothard line, including
four branches, may be taken at 291 ki-
lometers (180) miles. It was at first con-
sidered that the yearly traffic for the first
ten years might be taken at 200,000
passengers and 400,000 tons of goods.
Subsequently the estimate has been
raised to about 250,000 passengers and
450,000 tons of goods ; the traffic being, of
course, greater on the main line through
the tunnel, and less on the branches.

With regard to the ratio between dead
weights and paying weights, it appears
that on the Swiss railways the number of
seats occupied as compared with the

number provided, taking the average
from 1874 to 1879, was 30.2 per cent.
On the St. Gothard line it was estimated
that it would be 40 per cent. Again, the
paying load for goods during the same
years on the Swiss railways averaged
27.51 per cent, of the gross load. Owing
to the heavy traffic of the St. Gothard
railway the proportion was estimated at
40 percent. The dead weight of car-
riages per seat provided, for four wheeled
American cars, varies from 221 to 305
kilograms. For the carriages of the St.
Gothard line it is 266 kilograms for four-
wheeled and 186 for eight-wheeled car-
riages. On the whole a weight of 250
kilograms per seat may be assumed,
which is equal to 605 kilograms per pas-
senger, or 700 kilograms for passenger
and dead weight together. Again, the
average of the Swiss lines for goods
wagons is 0.55 ton as the tare per ton
gross weight hauled ; and since only 40
per cent, of the gross capacity is utilized,
the dead weight per ton of paying load
is 1.375 ton, giving 2.375 tons as gross
weight per ton of paying load. Hence
results the following as the estimated
traffic on the various divisions of the St.
Gothard railway :

254

VAN NOSTKAND's ENGINEEKING MAGAZINE.

Line.

Traffic.

Gross weight
hauled per annum.

Tons.

(The metric ton=

0.9842 av. ton.

Ditto per day.
Tons.

1 Goods - . .

19,600
187,500

537

3,254

Bellinzona to Chiasso

175,000
960,000

480

2,606

Bellinzona to Pino

j Passenger

( Goods

175,000
237,000

480

651

Bellinzona to Locarno

| Goods

105,000
23,750

288

With regard to speed, the actual
speeds on the Mont Cenis (gradient 1 in
33) are :

Express trains.
Ordinary " .
Goods ' " .

15 to 18 miles an hour.
14 to 16
12 to 14

On the Brenner-Semmering the speeds
are :

Passenger trains, average 12 miles an hour.
Goods " " 7

Herr Gottschalk holds tliat a goods
engine on such lines, gradient 1 in 40,
should never exceed 9 miles an hour.
Herr Hellwag fixed the conditions for
the St. Gothard railway as follows :

Miles an

hour.

In the valley, max. j Passenger trains, 27

gradient 1 in 100. . . ( Goods " 10

In the mount'ns, max. j Passenger " 13

gradient, 2.7 in 100. { Goods " 7

In the tunnel, max. j Passenger " 18

gradient, 2. 58 in 100 ] Goods ' ' 9

With regard to the number of trains,
allowing four hours out of the twenty-
four for delays, and that passenger trains
are thirty- one minutes, and goods trains
sixty-three minutes, between Goschenen
and Airolo, the possible number of trains
per day would be twenty-five. If a cross-
ing place were provided in the tunnel,
the number could be raised to thirty-
seven. With regard to the train loads,
the terrible effects of a train breaking
loose on such a line make it necessary to
limit this according to the strength of
the couplings. Even with the latest form
of couplings it is considered that the
total stress should not exceed 6J tons.
On the Semmering, on gradients 1 in 40
and curves of 200 yards radius, this stress
is reached with goods trains of 200 tons.

On the St. Gothard railway the gradient
is 1 in 37, but the curves have only 300-
yards radius. The result will therefore
be the same, and the greatest weight of
train must therefore be taken as 200
tons.

The locomotives necessary for convey-
ing the traffic under these conditions for
the first year were estimated as follows :

12 engines, 4-coupled, 25 tons adhesion wt.
19 " 6 " 38
17 " 8 " 52

Total 48 " 1,906

For subsequent years the number was
taken at eighty. The railway already
possesses fourteen engines, and thirty-
four new ones will therefore be required
when the line is opened. In October,
1880, the directors contracted for the
supply of thirty- seven engines as fol-
lows :

Six tank-engines, four-coupled, with a
four-wheeled bogie, for the passenger
trains on the valley sections : diameter
of cylinder, 16| inches ; stroke, 24 inches ;
total heating surface, 1,120 square feet ;
weight loaded, 42.7 tons ; smallest ad-
hesion weight, 22.5 tons.

Fifteen tank-engines, six-coupled, with
a radial leading axle, for passenger trains
on the mountain section : diameter of
cylinders, 18.8 inches ; stroke, 24 inches ;
total heating surface, 1,302 square feet ;
weight loaded, 51.5 tons ; smallest ad-
hesion weight, 33 tons.

Sixteen tender-engines, with six wheels
all coupled, for goods trains : diameter
of cylinders, 18.8 inches ; stroke 25
inches ; total heating surface, 1,378
square feet ; weight loaded, 61 tons ;
smallest adhesion weight, 38 tons. These

THE ROLLING STOCK OF THE ST. GOTIIARD RAILWAY.

255

engines have tanks for carrying 4 tons
of ballast water, to bring up the ad-
hesion weight, if required, to 42 tons.

The building of the heavy tank-engines
was subsequently suspended.

The Council of Management of the
railway have pronounced the above type
of tender-locomotive to be ill adapted to
the railway, and the number insufficient.

In comparing the two classes — tender-
and tank-engines — it will be assumed
that the tank-engines have 42 tons as
adhesion weight at starting, with 10 tons
on the leading axle, and the tender-en-
gines that have the same adhesion weight,
with a tender weighing 11 tons empty,
and 23 tons full.

The following are the advantages of
the tender-engine : — (1) Simplicity, (2)
accessibility of parts, (3) lower level of
center of gravity, (4) greater range in
choice of construction and dimensions,
(5) constant load on the axle, (6) constant
tractive force, (7) greater tendency to
preserve the direction in case of derail-
ment, (8) more room for water and coal,
(9) consequent capability of taking a
worse quality of coal, (10) less risk for
men and passengers in accidents, from
the presence of the tender, (11) use of
strong tender-brakes.

The disadvantages are as follows : —

(1) Overhang of the fire-box, causing ob-
jectionable and dangerous oscillations,

(2) stiffness of the coupling between en-
gine and tender, (3) great wear of the
leading wheel flanges, (4) consequent
wear of permanent way, (5) greater prob-
ability of derailment from this cause and
increased cost of maintenance, (6) large
difference between the total weight and
the weight utilized for adhesion, occasion-
ing either the too heavy construction of
some parts, or the carrying of ballast,
(7) impossibility of completely inclosing
the driver's stand.

On the other hand, the advantages of
the tank-engine, with free leading axle,
are as follow : — (1) Secure fixing of the
boiler, (2) easy traveling, (3) safety on
curves, (4) low resistance on curves, (5)
uniform wear of the wheel flanges, (6)
reduced wear of the permanent way, (7)
possibility of inclosing the driver's stand.

The disadvantages are as follows : — (1)
Variable load on axle, (2) variable tractive
force, (3) confined space for driver, &c,
(4) difficulty of access to some parts, (5)

tendency to leave the direction in derail-
ment, (6) loss of the tender-brakes.

As regards repair and maintenance, ex-
perience shows that a tank-engine costs
more than a tender-engine ; but not more
than engine and tender together.

On the St. Gothard railway it would
not pay to burn inferior coal, as the
freight is very heavy ; hence the large
coal space of the tender-engine is not
needed. The leading bogie is not, of
course, a feature of tank-engines alone,
but its use is there much more easy and
valuable. The question of tender-brakes
has lost much of its importance now that
many goods wagons have brakes, and
that automatic continuous brakes are
coming so rapidly into the field.

As to the efficiency of the engines, the
gradient in the Kehr tunnel on the
Northern division, is 2.3 per cent. The
continual wetness of the rails diminishes
the resistance on curves, but also di-
minishes the adhesion, which must not
be calculated at more than one-eighth.
On the south side there are gradients in
the open up to 2.7 per cent., so that the
adhesion is the same on both sides. The
resistance may be taken as 0.005 ton per
ton of engine and train. Then the great-
est weight hauled will be 187 tons, giv-
ing 122 tons of train-load for the tender-
engine, and 135 tons for the tank-engine.
The latter will, of course, lose tractive
force, as its water and coal diminishes ;
but it appears that when it has lost 5J
tons its train load will still be equal to
that of the tender-engine.

The consumption of fuel may be taken
as for the Brenner, viz, 94 kilograms
(207 lbs.) per 1,000 ton-kilometers. The
weight of the trains may also be assumed
as the same, say 65 tons. This, with
the tank- engine, gives a total weight of
110 tons. It follows that the whole
length of 90 kilometers, from Erstfeld
to Biasca, might be run with 900 kilo-
grams (1,980 lbs.) of coal, and 7 cubic
meters of water, and therefore without
replenishing. There must always, how-
ever, be a stoppage before entering the
tunnel, and water and coal can be easily
taken in at that time. The weight of
the goods trains may be taken at 120
tons, or 169 tons with the engine. This
would require 10 cubic meters of water
and 1,400 kilograms of coal. Coal and
water must therefore be taken in once

VAN NOSTRAND'S ENGINEERING MAGAZINE.

during the journey, whether tank-en-
gines or tender-engines be used.

The lower dead weight of the tank- en-
gine is, of course, a saving in point of
fuel. It is calculated that on the mount-
ain part of the line the saving would
amount to 4,200 francs per annum. It
appears, then, that tank-engines are
equally efficient, safer, easier in running,
and more economical, in wear and tear
and in fuel, than the corresponding
tender-engines. Since some tender-en-
gines have already been ordered, it can
only be suggested that half the stock
should be in one form and half in the
other.

As to the performance of the engines,
the number of engines employed on the
five main Swiss lines, in the summer of
1880, was as follows :

In service 276, or 60.8 per cent.

In reserve 71, or 16.6 per cent.

Under repair 107, or 23.6 per cent.

Taking these in round numbers as 60,
20, and 20 per cent., it is found that the
St. Gothard line will require fifty-one en-
gines in all.

The annual mileage of the engines on
the Swiss normal lines has 'steadily de-
clined from 30,393 kilometers in 1874 to
24,839 in 1879. Herr Hellwag assumes
that, on the St. Gothard line, the pas-
senger engines will run 30,000 kilometers,
and the goods engines 34,000 kilometers
per annum, on the mountain section.
The question here is the time that the
driver's firemen will practically work in
each twenty-four hours.

On the Swiss railways the average
time is 15^ hours per day in service, of
which 7^ are actual running. In Ger-
many the figures are 17.4 and 9.6 re-
spectively. On the French East Railway
they are 10 and 5 for express trains, 10
and 6 for passenger trains, and 12 and 1\
for goods trains. On the Belgian rail-
ways the average is 10J hours in service.
For the St. Gothard railway the hours
of service may be assumed to be 14, of
which 6 will be actual traveling, for
quick trains, and 9 for slow trains ; and
this for two hundred and twenty days
per annum. Assuming the speed to be
22 kilometers per hour for quick trains,
and 12 for slow trains, it is found that
the passenger engines will run 43,000
kilometers, and the goods engines 24,000
kilometers per annum, on the mountain

section of the line. On the valley sec-
tions, where the speeds are 45 and 17
kilometers, the corresponding numbers
will be 48,000 and 30,000 kilometers per
annum. These figures are confirmed by
the mileage of certain engines on the
existing Swiss railways.

To obtain a high mileage for locomo-
tives the following are the chief points to
be attended to :

(1) The engines must be properly con-
structed, and of good material.

(2) There must be a good distribution
of the work, both for the drivers and the
engines.

(3) There must be a well-equipped
work-shop, to make sound and rapid re-
pairs.

As an illustration of No. 2, the total
weight taken over the Mont Cenis line
in 1878, exclusive of engines, was 1,024,-
500 tons, or 2,807 tons per day. This
was hauled by thirty-seven engines, hav-
ing a total adhesion weight of 1,798 tons.
Adding the tenders at 20 tons each, the
total engine weight working per day
was 2,538 tons, to haul only 2,807 tons
of train load; in other words, the en-
gine weight 90 per cent, of the train
weight, and three times as great as the
paying weight.

A table is given, which shows the
amount of traffic which could be worked
over the St. Gothard line by the thirty-
one engines ordered, assuming their per-
formances to be as above described.
It appears that the performance of the
passenger engines would be greater
than that estimated as necessary on the
line, but that of the goods engines con-
siderably less. This difficulty might be
overcome for a time, if the directors
resist the temptation of opening the
line with a large service of trains, which,
in the case of a trunk line across a
mountain chain, is quite unnecessary.
It remains, however, that they should
at once proceed with the design and
construction of goods engines of a more
powerful character. The type of these
engines will be mainly determined by
the three following conditions: (1)
Utilization of the whole weight for ad-
hesion ; (2) fixed wheel-base of less
than 3 meters ; (3) load per axle of not
more than 12 tons.

On the Austrian Southern Railway an
eight-coupled engine, of 52 tons adhe-

ENGINEERING NOTES.

257

sion- weight, hauls a train of 200 tons
total weight (the maximum which has
been suggested for the St. Gothard
line), including 25 tons for the tender. :
A 70-ton tank engine, with twelve driv-
ing wheels, would haul, with a smaller |
consumption of fuel, about 30 per cent. I
more of train weight than the tender
engine; in other words, would take up
in three trips a weight for which the
other would require four. Such a double
six-coupled engine would practically haul j
300 tons across the mountain, and could
thus convey the maximum daily train
weight of 3,250 tons in eleven trains ;
adding four mixed and ten passenger
trains, the total number per day would
be twenty-five : which could be worked
without a crossing place in the great
tunnel. The conclusion is that twelve-
wheeled engines of this kind, more or
less resembling the Fairlie type (of
which three hundred have now been
built) should be used for the St. Goth-
ard line. [It is not stated how the
difficulty of excessive strain on the coup-
lings is to be got over.]

REPORTS OF ENGINEERING SOCIETIES.

rpHE American Society of Civil Ekgi-
J_ neers. — The last number of the Trans-
actions contains:

Paper No. 238. — Subaqueous Underpin-
ning. By A. G. Menoc'al.

Paper No. 239.— The Mean Velocity of
Streams Flowing in Natural Channels. By
Robert E. McMath.

Engineers' Club of Philadelphia. — The
last issue of the Proceedings contains:

Paper No. 3. — Applications of Logarithms
to Problems in Gearing. By Milford Lewis.

Paper No. 4. — Working Strength of Bridge
Posts. By G. P. Bland.

Paper No. 5. — Thickness of Cast Iron Pipes.
By P. H. Baerman.

Paper No. 6. — Resistance to Traction on
Roads. Rudolph Herring.

Paper No. 7. — Philadelphia and Long Branch
Railway. By C. S. D'Invilliers.

Paper No. 8. — Brick-work under Water
Pressure.— By D. McN. Strauffer.

The Strength of Wrought Iron Columns.-
By Thos. M. Cleeman.

ENGINEERING NOTES.

The Water Supply of Alexandria. —
Alexandria has been threatened with a
water famine. Its supply is drawn from the
Mahmoudie Canal, which communicates with
the Nile at Atfeh. Into this canal runs also the
Khatatbeh Canal, which at one time drew its
Vol. XXVII.— No. 3—18.

supply from the Raid Canal, but now gets its
water from large pumps erect <1 last year by
Messrs. Eastonand Anderson, Erith Ironworks,
Kent. These pumps are fixed at Khatatbeh.
There are ten of Airy and Anderson's patent
screw pumps, each 12ft. diameter, and capable
of delivering 144 tons of water per minute to
a height of 10ft. 6in. Eight pumps are worked
together, delivering 1152 tons per minute.
They are driven by two pairs of compound
inverted direct-acting engines of the marine
type, running at 75 revolutions per minute
under 65 lb. steam. There is also one reserve
engine. The pumps have been working regu-
larly since the middle of April, and were
stopped about the 18th inst. in consequence of
the danger to the staff employed about them.
The pumps were made for the Behera Irriga-
tion Company, for which Messrs. Easton and
Co., of London and Cairo, were consulting
engineers. The works were under the im-
mediate charge of Mr. H. C. Anderson, at
Cairo. On the 12th of June, a 24 hours' run
gave the extraordinary high duty of 1 -horse
power of water lifted 3.25 meters per hour for
3.05 lb. of Welsh coal which had deteriorated
considerably from long exposure to a tropical
sun. The duty has ranged between 78 and 85
per cent., that is, the ratio between the work
done in lifting water and the indicated horse-
power. We understand that a guard has been
sent out to protect Atfeh. If the works there
are stopped, Alexandrta will be without water,
but this is not now feared.

Tunnel Under the Boston Mountain. —
At 5 o'clock this morning the wrorkmen
of the two ends of the tunnel under the Boston
Mountain, 23 miles south of this city, on the
line of the St. Louis & San Francisco Railway,
shook hands through the division wall. A few
minutes later Mr. McDonald, the superin-
tendent of the tunnel works, under the charge
of Cameron & Holly, Col. Cameron , and Capt.
Hinckley, division superintendent, passed
through the aperture made by the completing
blows of the workmen. Track will be com-
pleted through the tunnel in two weeks. This
is the finishing stroke on the St. Louis and
great Southwestern thoroughfare. The hole is
1,730 ft. in length, and is the most important
work of the kind in the State. The big
bridge, 800 ft. long and 123 ft. high, just south
of the Boston Mountain, is also about com-
pleted. Trains from St. Louis to Fort Smith,
by way of the 'Frisco, will run on the 15th of
August next.

Tjn he Forth Bridge. —There has just been

_L completed on the island of Inchgarvie,the

spot where the central piers of the Forth

Bridge structure are to rest, a wind gauge for

the purpose of indicating the lateral pressure

of the force of the wind from east to west.

; The erection is composed of an enormous mass

of heavy timber — about fifty tons in all — which

; is placed upon the square tower and upwards

| of the old castle on the island. The top of the

I erection is about 100 feet above high-water

, level, and the apparatus upon which the wind

exerts its force is a large flat screen of thick

planks. This screen exposes to the wind about

258

van nostrand's engineering magazine.

200 square feet of a surface, and is mounted
on small roller- wheels moving on iron rails
parallel to each other. At each corner, and on
both sides, are placed strong spiral springs re-
sembling in some degree the buffer-springs of
locomotives. On the east side of the screen
are fixed steel wire conductors, by which the
wind pressure is led to the indicator below.
The apparatus is now in good working order,
and the highest pressure registered since the
erection is only one-fourth of the strain which
the bridge is calculated to stand.

The Panama Canal. — The latest reports
from the Isthmus are again rose-colored,
or intended to be so. The line of the canal
through the virgin forest has been almost en-
tirely cleared. The great cutting of the Cor-
dilleras, at the highest point of its course, has
been begun. The Couvreux excavators are in
operation — it is said, much to the suprise of
the Americans, who had predicted that they
would not work. It seems to be considered a
matter for great congratulation that the death-
rate has fallen below 70 per 1000, at which
figure it had long stood; and the sanitary con-
dition of the employes is held to be much im-
proved.

IRON AND STEEL NOTES.

I eon and Steel Production in Russia. —
The production of pig-iron was, in —

1874 : . ... 23,212,772 puds.

1875 26,061,323 "

1876 26,956,350 "

1877 24,403,319 '•

1878 25,472,540 "

Averasre 25,221,360

and in 1879, 26,412,806.

The quantity of steel turned out rose in —

1874 to 526,778 puds.

1875 " 789,253 "

1*76 " 1,093,719 '«

1877 " 2,702,863 "

1878 " 5,801,754 "

Average 2,182,873

and in 1879, to 12,929,170

The production of pig-iron was, therefore,
increased by 940,266 puds, with respect to the
previous year's returns, and by 1,191,446 puds,
as compared with the average of the five-
yearly period.

In wrought iron there was an increase of
432,125 puds over the figure of the previous
year, and a diminution of 361,423 puds from
the average of the years from 1874 to 1878.
This diminution is the natural consequence of
the rapidly increasing production of steel,
which has made extraordinary progress, espec-
ially at St. Petersburg, in Poland, in the Oural,
and in the Brjansk establishments.

The year 1879 shows, for steel, an increase of
7,127,416 puds over the figures of the preceding
year, and of 10,747,297 puds over the five-
yearly average. This increase in the steel
manufacture is almost entirely due to the

numerous orders for the State railways, and to
the premiums granted by the Government.

The manufacture of wrought iron and steel
barely amounts to half the demand. To form
a just idea of the measure in which the produc-
tion is inferior to the consumption, it is suffi-
cient to call to mind the quantity of rails
necessary for tho construction and repairs of
the iron ways of the Empire. In 1879, there
were 21,841 versts of railway opened, without
counting the sidings. Besides, the Russian
railway system receives marked additions every
year; and the double line of way is coming
generally into use. Besides rails, large quanti-
ties of iron and steel are absorbed in the con-
struction of bridges, the fixing of the rails, the
rolling stock, and in buildings. — Journal of
Society of Arts.

Yield of Steel Plates. — The steel de-
partment of the Dalzell Iron and Steel
Works, at Motherwell— Mr. David Colvill's—
continues taxed to its utmost capacity in the
manufacture of ship and boiler-plates, beams
and bar-. The yield on occasional shifts
reaches astonishing figures. The slabbing
hammer is a fine powerful tool capable of
giving a blow exceeding 400 foot-tons, and is
worked in connection with three gas heating
furnaces. The plate rolling mill has two pairs
of 28in. rolls by 8ft. long, and is driven by a
magnificent pair of Ramsbottom reversing
engines. Two large gas furnaces heat the slabs
for this mill. The following figures from Mr.
Colville's books give the material charged and
the finished ship and boiler-plates yielded
during two succeeding shifts of twelve hours
each on the 9th inst. : — Hammer: Day shift,
ingots charged, 73 tons 7 cwt, 3 qr. ; slabs and
billets produced, 67 tons 0 cwt. 3 qr. Ham-
mer: night shift, ingots charged, 79 tons Ocwt.
2 qr. 21 lbs. ; slabs and billets produced, 73
tons 14 cwt. 2 qr 21 lb. Plate mill: day shift,
slabs charged, 66 tons 0 cwt. 3 qr. 69 lb. , finished
plates yielded, 52 tons. 5 cwt. 0 qr. 3 lb.
Plate mill : night shif r, slabs charged, 67 tons
13 cwt. 1 qr. 23 lb. ; finished plates yielded, 52
tons 3 cwt. 1 qr. 3 lb. With a single hammer
and plate mill worked with a similar furnace
power this production has never, we believe,
been surpassed.

ORDNANCE AND NAVAL.

The British Navy. — A parliamentary re-
turn just issued shows the amount of
shipping — tons weight of hull — estimated and
built from the year 1865-6 to the year 1881-2
for the British, navy. The total number of
ironclads, and wooden, iron, and composite
vessels actually built during that period in her
Majesty's dockyards and by contract amounted
to 322,952 tons, to the value of £15,174,690.
The smallest quantity of shipping built in any
one year during that period was 13,566 tons in
1866-7, and the largest quantity in the year fol-
lowing, when 27,422 tons were built. The
greatest value represented by the shipping con-
structed in one year was in 1876-7, when
£1,423,418 were expended in the construction

OKDNANCE AND NAVAL.

269

of 34,230 tons of shipping, principally com-
posite vessels. Tin' return also includes a
statement of the amount of money proposed to
be spout on labor, and that actually spent on
the several ships building in her Majesty's
dockyards during the year 1881-8'-?. showing
the corresponding tonnage. For armored
>hip> the amount proposed to he spent was
19,367, and that actually spent £850,535,
upon a tonnage actually built of 10,7-48. For
unarmored vessels, the amount proposed to be
spent was £137,956, ami that actually spent
£169,939, upon 4690 tons actually built. The
amount of unarmored ships proposed to be
built by contract during 1881-2 was 4050 tons,
at an expenditure of 220,645; the amount act-
ually built was 3172 tons, for which £11)4. 119
has been paid. There were no armored ships
built by contract during that period.

Qtekl faced Armor Plates. — Some recent
O trials have been made of steel faced armor
plates for the protection of the Collingw<>od,
now under construction at Pembroke. In our
issue of January 20, we recorded the results of
the testing of a plate measuring 8 feet in height
by 6 feet in breadth, with a thickness of 11
inches, of which the steel face was 3% inches.
It was constructed according to AVilson's pro-
as, and wTas fired at three times by the 9-inch
12-to i gun on board the Nettle at Portsmouth.
Of the few cracks which were produced by the
impacts, only two extended to the edge of the
plate, and none went beyond the deptli of the
steel face, so that the T1^" inches of iron back-
ing remained whole and unbroken at the end of
the ordeal. The maximum penetration worked
by the 250-pound projectile was 4.7 inches,
while the bulges at the back never exceeded
five-eighths of au inch. The hardness, tough-
ness, and resistance of the plate were such that
it was felt that the 9-inch gun had ceased to be
an adequate test, and it was accordingly
resolved not only to make use of the 10-inch
18-ton gun in all subsequent armor testing,
but to subject the already injured Cammed
plate to an attack from the larger caliber.
This wholly exceptional trial took place
recently at Portsmouth, but the results of the
firinx were only ascertained on Tuesday of
last week, when the plate had been removed
from the bulkhead. In order that the tre-
mendous character of the second ordeal may be
fully understood, it may be meutioned that the
initial velocity of the 9 inch projectile propelled
with a battering charge of pebble powder is 1420
feet per second, and that its energy at the
muzzle is 125 foot tons per inch of circum- !
ference. The projectile of the 10-inch gun, on
the other hand, while it has a slightly less
initial velocty, or 1364 fet-t per second, has an
energy of 166-foot tons. It was thought that
one shot from the large gun at 30 feet would be
sufficient to complete the disintegration of the
plate, and, as a matter of fact, so confident
were the gunnery officers that a second round
would not be required that only one shot
and charge were brought from below. The
projectile hit the target about a foot below the
indent inflicted by the second shot, at the
previous trial, and at equal distances from the [

right and lower edges. To the surprise of
everybody ihe iinpaet had apparently no effect
Whatever upon the plate, no new cracks being
produced, while the old ones remained pre-
cisely as they were. The head of the shot
remained imbedded in the plate. Three more
shots were discharged at ihe plate near the
margin. Xos. 2 and 3 developed former cracks
only, while the last round caused a new crack
to appear, extending from the indeut to the
edge. In no instance, however, was the plate
cracked through, the injury stopping short at
the point where the steel face is welded to the
iron backing. To all appearances the plate has
suffered little injur}' from the second bombard-
ment, and it is a remarkable circumstance, and
at present wholly inexplicable, that, while the
9-iuch gun made an indent on the surface of
the plate 4.7 inches deep, the heavier gun with
its increased striking energy only penetrated
4.4 inches. On the plate being taken from the
bulkhead it was found that the bulges resulting
from the first trial in January were five-eighths
of an inch, while the bulges produced by the
10-inch shot were one inch and one sixteenth in
extent. In both instances the curvature of the
surface was free from cracks. This plate is
the most successful which has yet been tested
at Portsmouth, aud the result of the severe
ordeal through which it has passed will proba-
bly reopen the question as to the expediency of
superseding the old protection of our men-of-
war by the new compound armor. — Engineer.

Twix-Screw Steamers for the Govern-
ment of the Argentine Republic. —
In JN"ovember of last year the Consul General
of France for the above republic entered in a
contract with Messrs. Edwards and Symes,
shipbuilders and engineers, Cubitt Town, Lon-
don, E., for the construction of four iron, light
draught twin-screw steamers On the 20th of
May the first of these steamers — .vhich is
named La Capitol, 85 ft. long, 15 ft. beam, and
7^2 fl- deep, with raised quarter-deck and fore-
castle— being nearly completed, proceeded
down the river to the measured mile at Long
Reach for her first official trial trip, and although
the weather was very unfavorable for the trial
of such a light draught vessel, yet she came up
to every expectation of her builders who
deserve hearty congratulations on tne results of
her trial trips. The mean draught of water was
under 3^2 ^L » an'' mean speed obtained on six
consecutive runs being as near as possible 11%
knots. On the 8th inst., she again proceeded
down the river for her second official trial trip,
having been loaded with twenty two tons of
cargo, making her mean draught of water 4 ft.
Under these conditions the mean speed attained
on six consecutive runs was 11 knots, thus
more than fultiling the expectations of her
builders, and the contract speed. The propel-
ling machinery is composed of two ordinary
independent compound surface condensing
eugines with high-pressure cylinder, 11 in. in
diameter, and low-pressure 20 iu. in diameter,
each set driving a screw 4 ft. in diameter. The
engines are supplied with steam from an
ordinary marine return tube boiler, which main-
tained a pressure throughout the trials of 90 lb.,

260

VAN NOSTRAND'S ENGINEERING MAGAZINE.

driving the engines 195 revolutions per minute,
the vacuum in both condensers being 26 in.,
the whole of the machinery working well
during the whole time the vessel was under
steam. The second vessel of the four ordered,
which is the first of a smaller class of the
above type, will proceed down the river next
week for her first official trial, the results of
which we shall give at a future date. The
builders have lately constructed two beautifully
fitted yachts, and besides the above four have
now in hand building a fire engine tug-boat,
three cargo steamers, a paddle steamer, besides
several smaller craft and steam launches. —
Engineer.

A Novel Atlantic Steamer. — We learn
that a Swedish engineer, Captain Lund-
borg, has just concluded an agreement with
Messrs. Charles L. Wright & Co., of New
York, for the construction of a fleet of steam-
ers, built on Captain Lundborg's patent, to
run between New York and Liverpool. The
inventor alleges to have founded a new basis
for the construction of fast-going vessels ; in
fact, he asserts that a vessel of his type will run
close upon 21 knots per hour, and thus accom-
plish the passage across the Atlantic in 5^
days. The dimensions of the vessel are: —
Length, 450 feet ; greatest width, 66 feet ;
draught, when loaded, 23 feet. Her weight is
10,881 tons, and she will be driven by four
engines of 4500 horse-power each, working two
propellers, as, according to the inventor, the
high rate of speed which he aims at cannot be
obtained by only one. The vessel will be
built entirely of steel, with a false bottom, and
watertight compartments of a novel cellular
form. The proportion between the length and
bread) h of the ship is 7 to 1, instead, as is the
case with steamers now in use, of 10-11 to 1,
and which the inventor states will increase her
strength. Above the water line she will not
exhibit any remarkable appearance, but the
submerged part of the hull is entirely different
in construction to any thing before tried in ship-
building, the widest part, 15 feet to 16 feet,
being far under the surface and ending aft
horizontally. The propellers run in the vessel's
hull, and not, as usual, on shafts outside it.
Another feature distinguishing Captain Lund-
borg's construction is the bow of the vessel,
which is sharpest at the water line — quite the
reverse of what is the case with vessels at
present in use — and broadens downwards to the
keel, a circumstance which, it is stated, will
add to the stability of the vessel and prevent
lurching. There will be two rudders steered
simultaneously, and the propellers are fixed
behind them. The construction of the first
steamer is to be commenced at once at Wash-
ington. She is to accommodate 600 first and
1000 second and third class passengers, whilst
carrying 2700 tons of coals and 550 tons of
goods. It is expected that about a year and a
half will be required for buiiding the vessel. —
Iron.

Trials of Machine Guns.— Captain Cod-
rington and the gunnery staff of Her Maj-
esty's ship Excellent have recently been oc-

cupied with final experiments in connection
with machine guns, and more especially with
a view of testing the efficacy of several naval
carriages and mountings proposed for machine
guns. The trials were held on board the Ex-
cellent and also upon Whale Island, in Ports-
mouth Harbor. A new mounting was tried for
the Nordenfelt 2-pounder gun of X% inch cali-
ber, as the mounting previously adopted was
found too light to secure the desired accuracy.
The new mounting was ascertained to be emi-
nently satisfactory, as will be seen from the re-
sults of the firing. Ten shells fired for accu-
racy with deliberate aim between each shot
gave, at 300 yards range, a mean deviation
from the point of impact of only 5% inches.
Seven out of the 10 shots hit the bull's-eye,
while the least favorable of the other three hits
was only three inches below the bull's-eye.
The gun was then fired for a minute for accu-
racy, combined with rapidity. With a com-
paratively slow aim, 12 shots only were dis-
charged during the time, but of these four were
bull's-eyes and eight inners, the mean devia-
tion being six inches. The next trial was to
fire at 300 range for a couple of minutes,
against two targets, 120 feet apart, and at dif
ferent levels, changing the aim from one target
to the other between each shot. Twenty-four
rounds were fired in the two minutes. One
missed the target in consequence of its being
fired before the gun was laid. Of the 23
hits, three bull's-eyes, six inners, and three
magpies were scored on the right target, and
four bull's-eyes, five inners, and two magpies
were scored on the left target. There were no
outers. The new mounting was thus proved
to do perfect justice to the gun, which at pre-
vious official trials, as from time to time re-
ported in these columns, has given great satis-
faction. With its high initial velocity of 1740
feet per second it has penetrated a 1% inch
steel plate, or 2% inches of iron, at 300 yards;
and it has fired as many as 29 shots in one
minute without deliberate aiming. The weight
of the gun is 3 cwt., and it has been
tried with solid steel projectiles, as well as
chilled and common shells. A new system
of bulwark mounting was afterwards tested
at the request of Mr. Nordenfelt, who had sent
clown three separate naval bulwark carriages
suitable for rifle caliber machine guns. These
consisted of a carriage for the heavier guns,
such as the Gardner 5-barreled and the Nor-
denfelt 10-barreled guns, weighing respectively
2% cwt. and 2 cwt. ; a carriage for medium
weight machine guns, such as the Gardner two
barreled and the Nordenfelt 5-barreled guns,
each weighing about one cwt.; and a bulwark
carriage for light machine guns, such as the
Gardner one-barreled and the Nordenfelt 3 bar-
reled, each of which weighs half a hundred
weight. These bulwark mountings were made
on the same lines as the carriage used by the
Navy for the Nordenfelt 1-inch gun with
screw motion, by means of band wheels for
elevating as well as traversing. The 10-barrel
Nordenfelt gun on the heavier mounting, when
firing at 300 yards 10 rounds from one barrel
without adjusting the aim between the shots,
gave a mean deviation of 6% inches. Of 100

RAILWAY NOTES.

261

rounds tired rapidly 83 hit within a quadrangle
of 7 feet by 5 feet. The tive barreled Nordenfelt
gun fixed OD the medium weight mounting,
gave, at 300 yards, 5l_> inches mean deviation
For 10 shots fired without adjustment of aim;
and of 50 tired rapidly 34 shots fell within a
quadrangle of B1^ feet by 6 feet. Tested m
the same manner on the light mounting, the
3-barrel Nordenfelt gave a mean deviation of 9
inches out of 10 shots; while '28 projectiles out
of 35) tired hit within a quadrangle of 7 feet by
6 feet, eight of the hits being bull's-eyes. The
three representative mountings were next
tested for strength and stability. The 10 barrel
Nordenfelt gun tired 3000 rounds in 3 min. 3
sec. ; the 5-barreled fired 1000 rounds in 1 min.
41 Bee.; and the 3-barrel gun tired 390 rounds
in 1 1-3 min. After this very severe test the
carriages were found to have lost none of their
steadiness and rigidity, while the guns, as well
as their carriages, worked at the end without
more exertion than at the beginning. The
guns had neither been cleaned after the accu-
racy trials, nor cleaned or oiled during the rapid
firing. The 10-barreled gun had one misfire
out of 3000, and the other guns had five mis-
fires out of 1390 rounds. The feeding and ex-
traction of all the guns worked without a
hitch or jamb of any kind, and the same man
fired the whole of the 4390 rounds without
difficulty. The whole of the guns used the
same old service Gatling cartridges as were
used at Shoeburyness in 1881, before the cart-
ridge rims were thickened to suit the Gard-
ner guus. In order to test the convenience of
the new carriages for following moving objects,
the guns were fired at alternate targets 120
feet apart, changing target between each dis-
charge, the gun being in each instance laid 45
deg. off the targets and 10 (leg. below the
level of the targets. The time of laying the
guus on the first target was counted within the
half-minute allowed for each gun. The 10-
barrel gun on the heavier mounting gave an
average of eight volleys (80 shots), the 5-bar-
rel, 11 volleys, and the 3-barrel, 12 volleys in
the half-minute. The 5-barrel gun was fired
from a special masthead mounting provided,
in addition to the three mountings previously
used. One hundred rounds were fired in 10
seconds, without deliberate aiming, at 300
yards, 59 shots hitting a target 12 feet by 6
feet. One hundred rounds were afterwards
fired in 27 seconds, with deliberate aiming be-
tween each volley, when 64 shots hit the target.
The 1-barrel gun, weighing 16 lbs., was fired
from a light portable deck carriage, with the gun
only 2 feet above the deck. The first 30 rounds
were fired in 11% seconds, and the second 30
rounds in 10 seconds — equal to a rapidity of
fire of 180 rounds per minute. Five thousand
five hundred rounds of Gatling cartridges in all
were fired without any hitch, thus showing
that Mr. Nordenfelt has entirely overcome the
disadvantages in feeding and exiracting rifle
cartridges which were remarked upon by the
Committee of Machine Guns in 1880 and 1881
oeburyness. — Iron.

RAILWAY NOTES.

Tl^iiK total number of deaths and injuries re-
1_ ported by the railway companies to the
Board of Trade during the year 1881 is given
in the following table:

Killed. Injured.
1881. 1880. 1881. 1880.
Passengers —

Accidents to trains, &c. 23 28 993 905
Accidents from other

causes 85 114 867 709

Servants —

Accidents to trains, &c. 19 23 168 118
Accidents from other

causes 502 523 2278 1962

Level crossings 83 74 32 30

Trespassers, including

suicides 328 330 131 156

Other persons 56 43 102 79

Total 1096 1135 4571 3959

In addition to the above — One passenger was
killed and 112 injured whilst ascending or
descending steps at stations; forty-four in-
jured by being struck with barrows, falling
over packages, &c, on station platforms;
thirty-six injured by falling off platforms; and
two killed and sixty injured from other causes.
Of servants of companies or contractors, six
were killed and 963 injured whilst loading, un-
loading, or sheeting wagons; one was killed and
303 were injured whilst moving or carrying
goods in warehouses, &c. ; five were killed and
172 injured whilst working at cranes or cap-
stans; fourteen were killed and 239 injured by
falling off platforms, ladders, scaffolds, &c. ;
eight were killed and 576 injured whilst work-
ing on the line of its sidings; and one was
killed and 231 were injured from various other
causes. Nine persons who were transacting
business on the companies' premises were also
killed, and 119 were injured — making a total in
this class of accidents of fifty-three persons killed
and 4015 injured. The total number of per-
sonal accidents reported to the Board of Trade
by the several railway companies during the
year amount to 1149 killed and 8676 injured.
For 1880 the total was 1180 killed and 6692
injured.

rpHE Northern Railway Company of France
_1_ is making a series of experiments with a
view to demonstrate that automatic action of
continuous brakes is not indispensable to
stoppage of the tail of a train in case of rup-
ture of the couplings in course of the ascent of
a hill. On rising and falling gradients the
stoppage of the tail of a train has been effected
with the vacuum brake by means of the com-
munication cord connecting the engine with
the rear wagon, where there must apparently
be another or second brake. At the moment
of rupture of this cord intentionally caused
the brake is set free by the descent of a
counterbalance weight, and the tail of the
train stopped. The experiments yet made have

2(32

van nostrand's engineering magazine.

been between Paris and Lille, in presence of
engineers from the Northern and the Belgian
State Railways, and are to be continued. The
Moniteur Industriel says the Belgian engineers
have asked for a fresh trial with the train run-
ning down a gradient on the line between Paris
and Montsoult.

The Swiss Railway Gazette — the Eisenhahn
of Zurich— reports that the Heberlein
automatic friction brake?, which were intro-
duced on trial on the Berne-Chaux-de-fonds
line about five months since, " have given such
thoroughly satisfactory results that the direc-
tion of the Jura Berne Lucerne Railway has
decided on the gradual adoption of these
brakes; and as a commencement, the express
and passenger trains on the Berne Lucerne line
are being fitted up in readiness for this season's
traffic. By the adoption of these powerful
brakes, which admit of stopping trams more
quickly at the stations and of descending steep
inclines at greater speed, a considerable accel-
eration of the train service can be secured,
which, in the case of the Berne Lucerne line
— which is 95 kilos, long and has seventeen
intermediate stations and inclines of 1 in 50 —
will amount to a reduction of half an hour in a
journey of three hours and a-half. It results
from the above (hat continuous brakes are not
only valuable in the case of express trains, but
also more especially in that of such passenger
trains as have to stop frequently at stations
only short distances apart, an$ which conse-
quently run very often between the stations
with even a greater speed than the actual ex-
press trains." The Heberlein brake has under-
gone important modifications since we illus-
trated it in our columns, and is daily making
important progress on numerous railways,
chiefly on the Continent. On the Royal Prus-
sian railways a large quantity of new stock is
being fitted with the Heberlein automatic brake,
and the Imperial German Board of Control for
Railways seems to be wholly in favor of this
mechanical brake, instead of brakes using
vacuum or air pressure.

In a paper recently read before the Institu-
tion of Civil Engineers in Ireland, en-
titled " Engineering Notes in Ceylon," by H.
F. A. Robinson, the author says: — "The center
of Ceylon is mountainous, and it is only of
late years that a trace was discovered by
which a railway could be brought up to Kandy
from the low country. As it is, the line runs
for about fifty miles nearly level, and then
ascends for twelve miles at a uniform gradient
of one in forty, with curves as sharp as five
and a-half chains. Two engines are necessary
to take the train up this pass, and the time for
the distance is over an hour. Coming down,
brakes are applied to every car separately,
which, as may be imagined, has the effect of
greatly shortening the life of the rolling stock.
The gauge of this line is 50 ft. 6 in., or the
ordinary Indian gauge. The sleepers, which
are all imported, are creoseted, which, besides
improving the sleeper, renders it impervious to
the ravages of white ants. The carriages are
very similar to those in ordinary use at home,

although they are better ventilated; but they
are very stuffy and uncomfortable, and, in
fact, not fit for the climate. American cars
would be much more suitable for the European
passenger traffic, as they have thorough ventila-
tion, which is so necessary in the East."

BOOK NOTICES.
publications received.

An Ephemeris of Materia Medica,
Pharmacy, Ther aped tics and Collat-
eral Information. ByE. R. Squibb, M. D. ;
E. H. Squibb, S. B., M. D. ; C. F. Squibb,
A. B., Brooklyn.

professional papers of the slgnal
Service.

No. 2. Isothermal Lines of the United States;.
1871-80. By Lieut. A. W. Greely.

No. 3. Chronological List of Auroras; 1870-
79. By Lieut. A. W. Greely.

No. 5. Construction and Maintenance of
Time-Balls. Prepared under direction of Brvt.
Maj. Gen. W. B. Hazen.

No. 6. Reduction of the Pressure Sea Level.
By Henry A. Hazen, A.M.

onthly Weather Report for May.

rriRANSACTIONS OF THE AMERICAN SOCIETY

JL of Mechanical Engineers.

proceedings of the engineers' club of
Philadelphia.

American Journal of Mathematics,
Vol. 4, No. 4.

IT" FFICLENCY OF STEAM ENGINES AND C()N-
JJ ditions of Economy, By Robert H.
Thurston, A.M., C.E.

Through the kindness of Mr James For-
rest, Secretary of the Institution of Civil
Engineers, we are in receipt of the following
valuable papers of the Institution:

Lancaster Waterworks Extension. By James
Mansergb, M.I.C.E.

Bridges in New Zealand. By Robert Hay,
A. M., I.C.E., and Harry P. Higginson,
M.I.C.E.

The burning of Town Refuse at Leeds. By
Charles Slagg, A.M., I. C.E.

Canal Navigation in Belgium. By A. Go-
bert.

The Rokuzo River Bridge. By Richard
Vicars Boyle, M.I.C.E.

New York Elevated Railroads. By Robert
Edward Johnston, M.I.C.E.

Light Scaffolding. By John Cundy,
A.M., I. C.E.

The Design of Structures to Resist Wind
Pressure. By Charles B. Bender.

The resistance of Viaducts to Sudden Gusts
of Wind. By Jules Gaudard (Republished in
this Magazine).

Steel for Structures. By Ewing Matheson,
M.I.C.E.

The Theory of the Gas Engine. By Dugald
Clerk (will be republished in the present vol-
ume of tnis Magazine).

BOOK NOTICES.

203

HorsK Dk\in.u;k and Samtaky Plumb
oro. By Wm. Paul Gerhard. Prov-
idence: E. L. Freeman.
This Is the best contribution to practical

sanitary science that we have yet Been. The
author clearly specifies the objects to be ac-
complished, and then in the most elaborate
manner describes the best approved mechanical
appliances devised for such accomplishment.

The illustrations are very numerous aud very
good.

We shall shortly republish a large portion of
this essay in this Magazine.

Elementary Dkcoration. By James
William Faeey, Jun. London: Crosby
Lock wood & Co.

But few subjects attract more general at-
tention at present than decoration. Onlj- the
rudimentary principles of house decoration arc
here aimed at, but the book is well filled with
useful information. The illustrations are nu-
merous and varied, and relate not only to dec-
orative forms but the place and method of
application.

This book is No. 229 of the well-known
Weale's Series.

AScnooL Course on Heat. By W. Lar-
deu, M.A. London : Sampson Low,
MarstOD & Searle.

The author informs us in a brief preface,
that the book is intended to supply a want felt
by many who are teaching the subject of heat
to such classes as those in the English public
schools. And furthermore that the chief char-
acteristics of the book are:

1st. That the reasonings and explanations
are at first very elementary; brevity being only
gradually attained.

2d. The writer has introduced collateral sub-
jects for the purposes of elucidation.

3d. The mathematical parts are carefully
treated, and typical examples are worked out.

4th. Questions on the subject matter of each
chapter are given at the end of it.

5i h. A shorter course than that presented by
the whole book is found quite completely given
by the omission of certain marked sections.

The typography is very good, and the illus-
trations, about 120 in number, are of excellent
character and well adapted to the text. This
book will do its best service with students who
are working without the aid of a teacher.

The Military Telegraph During the
Civil War in the United States.
By William R. Plum. LL.B. New York :
D. Van Nostrand.

The object of this work is to show the valu-
able services rendered by the Military Tele-
graph Corps in the late Civil War. In order to
illustrate the importance of the Telegraph, and
give it its due setting, it was considered neces-
sary to give a running account of the struggle
itself. In this the author has been greatly
aided by important telegrams, and other papers,
official and otherwise, which have never been
published, and by many Southern operators
who have furnished interesting and important
facts from their point of view. The author
has striven to be accurate and just; avoiding

debatable questions, and seeking concisely to
state material facts.

The ancient and modern methods of com-
munication are explained; also the Federal and
Confederate cipher system.

The work consists of 2 octavo volumes with
a total of 767 pages, with portraits and illus-
trations.

rpiHE Boileb-Maker's Ready Reckoner.

JL By John Courtney ; Revised by D. Kinnear
Clark, C.E. London: Crosby Lock wood &
Co.

This is but little more than a book of con-
venient tables for the boiler maker. Enough
practical geometry precedes the tables to in-
struct the artisan in the method of laying out
his work.

The tables afford the piece- work plater who
is paid by the ton, how to find the weight of
his iron when he has the size of it. Riveters
may reckon the payment of the holder on from
the rivet table. Smiths may get information
in regard to circumferences of circles of angle
iron and plate iron.

The work is designed to save much vex-
atious and intricate work to the artisan of riv-
eted iron structures.

Report of the Solar Eclipsk of July,
1878. By Cleveland Abbe. Washing-
ton: Government Printing Office.

This Report forms No. 1 of the Professional
Papers of the Signal Service.

Chapter I. is chiefly devoted to the instruc-
tions issued for the benefit of observers along
the line of totality.

Chapter II. details the operations of the
Signal Service Expedition to Pike's Peak, and
is the more important part of the Report.

Chapter III. is a collection of the miscel-
laneous observations and reports to the number
of eighty.

Chapter IV. gives a summary of results.

A large number of sketches of the corona are
appended.

Railroad Economics. Science Series,
No. 59. Strength of Wrought Iron
Bridge Members. Science Series, No. 60.
By S. W. Robinson, C.E. New York: D. Van
Nostrand.

Our readers have already had an opportunity
of judging of the merits of these two treatises,
as they are both reprints from the Magazine.

The first one contains two topics quite of an
original character and of undoubted value to
railway engineers: The Bridge Indicator and
Easement Curves.

In Part II. of the second one is found an ex-
ceedingly concise compendium of Practical
Formulas for Beams, Struts, and Columns.

Electric Lighting. Translated from the
French of Le Comte Th. Du Moncel. By
Robert Routledge, F.C.S. . London: George
Rutledge & Sons.

This work is well designed to meet the wants
of those who profess only a general knowledge
of physical science, and who desire to under-
stand the relative merits of the many so-called
systems of Electric Lighting.

Part I . After a brief historical sketch of pub-

264

yan nostrand's engineering magazine.

lie electric lighting, the author defines the terms
necessarily used in discussing the comparative
merits of the various modern magneto-electric
and dynamo machines.

Part II . Describes the generators of electric
currents for the production of light, taken in
the order of their invention. This leads to a
full description of the various magneto ma-
chines with their theory of action.

Part III. Gives full descriptions of the
Electric Lamps including their regulators.

Part IY. Deals with the economic question
of cost of Electric Lighting.

Part V. Discusses the actual and probable
applications of the Electric Light

The original work gives us the state of prog-
ress down to 1880. An appendix by the trans-
lator gives descriptions of the later lamps.

The illustrations are numerous.

Linear Associative Algebra. By Benja-
min Peirce, LL . D . New York : D. Yan
Nostrand.

The number who will read this work and at-
tain a thorough understanding of it is certainly
quite limited. But of the mathematical stu-
dents who in studying it will reap great benefit
through the more expanded views of mathe-
matical research they will gain, the number is,
without doubt, very great.

It is the work of one of the first mathematical
minds of our day, and only accomplished
mathematicians can tell us how valuable it is.

Lithographed copies of the treatise were dis-
tributed by the author among %is friends in
1870. It was printed first for the American
Journal of Mathematics. The present edition
is a new one, with addenda and notes by C S.
Peirce, the son of the author.

The book is a quarto of 133 pages and is
beautifully printed.

MISCELLANEOUS.

MBremond states as a general law that,
. by reason of rarefaction of air, ' ' gas
loses at least one liter of illuminating power
per 50 meters of altitude." He give the details
of an interesting experiment made on the
Northern Railroad of Spain, observations being
taken at various altitudes on the way from
Madrid, 595 meters above sea-level, to La Can-
ada, a station 1373 meters above sea-level.
The following table, in which Paris is taken
as a unit of comparison, gives some of the re-
sults of his experiments:

Barometric
Altitude, pressure, Illuminat-
City. meters, millimeters, ing power.

Paris 0 0.754 105

Yienna... 68 0.747 103

Moscow.. . 235 0.732 99

Madrid.... 573 0.705 87

Mexico.... 2212 0.572 30

IpROM a recent work on "Metal Alloys,"
' published in Germany, the author, Mr.
Guetlier, gives a few suggestions on the sub-
ject of fusing the metals, with which the Jew-
elers' Journal prefaces the recipes selected. (1)
The melting pot should be red-hot — a white

heat is better — and those metals first placed in
it which require the most heat to fuse them.
(2) Put the metals in the melting pot in strict
order, following exactly the different fusing
points from the highest degree of temperature
required down to the lowest, in regular se-
quence, and being especially careful to refrain
from adding tbe next metal until those already
in the pot are completely melted. (3) When
the metals fused together in the crucible re-
quire very different temperatures to melt them
a layer of charcoal should be placed upon them,
or if there is much tin in the alloy a layer of
sand should be used. (4) The molten mass
should be vigorously stirred with a stick, and
even while pouring it into another vessel the
stirring should not be relaxed. (5) Another
hint is to use a little old alloy in making new,
if there is any on hand, and the concluding
word of caution is to make sure that the melt-
ing pots are absolutely clean and free from any
traces of former operations.

Tn the opinion of Herr W. Hempel the hard-
ening of vulcanized india-rubber, which
takes place with piping and other goods after
a short period of use, is caused by the gradual
evaporation of the solvent liquids contained in
the india-rubber, and introduced during the
process of vulcanization. Herr Hempel has
made experiments for a number of years in or-
der to find a method of preserving the india-
rubber. He now finds that keeping in an at-
mosphere saturated with the vapors of the
solvents answers the purpose. India-rubber
stoppers, tubing, &c, which still possess their
elasticity are to be kept in vessels containing a
dish filled with common petroleum. Keeping
in wooden boxes is objectionable, while keep-
ing in air-tight glass vessels alone is sufficient
to preserve india-rubber for a long time. Ex-
posure to light should be avoided as much as
possible. Old hard india-rubber may be soft-
ened again by letting the vapor of carbon
bisulphide act upon it. As soon as it has be-
come soft it must be removed from the carbon
bisulphide atmosphere and kept in the above
way. Hard stoppers, the Journal of the So-
ciety of Chemical Industry says, are easily
made fit for use again in this manner, but the
elastic properties of tubing cannot well be re-
stored.

W Spring has shown that, when a mix-
. ture of bismuth tilings, cadmium, and
tin, in the proportions necessary for the forma-
tion of Wood's alloy, is subjected to a pressure
of 7,500 atmospheres, the mass thus obtained
powdered and again subjected to the same
pressure, a metallic block is formed which has
all the physical properties of the alloy. Its
specific gravity, color, hardness, brittleness,
and fracture are the same ; and when thrown
into water heated to 70 degrees it melts at once.
In like manner Rose's metal was made by sub-
jecting the proper mixture of lead, bismuth,
and tin to high pressure. If zinc and copper
filings are repeatedly subjected to pressure, a
mass resembling brass is finally obtained. If,
however, on the other hand, the attempt is
made to "squirt" brass, zinc and tin will be
squirted, and the copper remain.

VAN NOSTRAND'S .

Engineering Magazine.

NO. CLXVL-OCTOBEK, 1882-VOL. XXVIL

HOUSE DRAINAGE AND SANITARY PLUMBING.

By WM. PAUL GERHARD, Civil and Sanitary Engineer, Newport, R.I.
Contributed to Van Nostrand's Engineering Magazine.

Many erroneous ideas still prevail about
sewer gas and its danger to health which
arises, by having so-called " modern con-
veniences" in our dwellings. It is the
purpose of this paper, without in any-
way adding to the "plumbing scare,"
clearly to define wherein the danger con-
sists, but at the same time to establish
rules for the proper draining and plumb-
ing of houses, which, if carefully ob-
served, will secure to the anxious house
owner work of superior quality and of a
positively safe character.

Plumbing fixtures, which were con-
sidered a luxury years ago, are now be-
lieved to be necessary, not only for
comfort and convenience, but also, and
even more so, for health and for cleanli-
ness. Even a small house is nowadays
generally provided with a kitchen sink, a
water closet, and sometimes a bath tub,
while in a costly modern residence, ar-
ranged with an elaborate system of
plumbing, we find kitchen, pantry and
scullery sinks, slop sinks, laundry tubs,
stationary wash basins in closets near
bedrooms, a great number of bath or
dressing rooms, with water closets, urin-
als, bath and foot tubs, bidets and other
fixtures.

The suggestions and recommendations
of this report apply with equal force to
Vol. XXVIL— No. 4—19.

the drainage and plumbing of tenements,
small houses, costly residences, villas,
apartment houses, hotels, factories,
school-houses or public buildings. As
every plumbing fixture is not only an
outlet for the waste water to the drain,
but possibly may become an inlet for
drain air, the danger increases with the
number of fixtures. A multitude of fix-
tures requires a large number of soil and
waste pipe stacks, and the chance of leak-
age of sewer gas through defective
joints increases correspondingly. But
be the house large or small, its drainage
and plmnbing system should always be
so arranged as entirely to exclude any
possibility of the escape of sewer gas.

SEWER GAS.

I shall, first, briefly consider what is
meant by the term " sewer gas." This
term, as Prof. W. Ripley Nichols has
truly said,* is " an unfortunate one, and
gives rise to a quite widespread but very
erroneous idea. Many seem to suppose
the ' sewer gas ' to be a distinct gaseous
substance, which is possessed of marked
distinguishing characteristics, which fills
the ordinary sewers and connecting

* See Prof. W. Ripley Nichols' report upon chemical
examination of the air of the Berkley street sewer,
in Boston, Mass., 1878.

266

VAN NOSTRAJSTD'fe ENGINEERING MAGAZINE.

drains, and which, as a tangible some-
thing, finds its way through any opening
made by chance or by intention, and
then, and only then, mixes with the at-
mospheric air."

Sewer gas is a mechanical mixture of a
number of well known gases, having
their origin in the decomposition of ani-
mal or vegetable matter, with atmospheric
air. This mixture is continually varying,
according to the more or less advanced
stage of putrefaction of the foul matters,
which form a sediment and a slimy coating
of the inner surfaces in drains and pipes.
It is also variable with the character of
this sediment or deposit, and with the
physical conditions (moisture, heat, etc.)
under which the decomposition takes
place.

The principal gases found in sewers
and drains are oxygen, nitrogen, carbonic
dioxide, carbonic oxide, ammonia, car-
bonate of ammonia, sulphide of ammo-
nium, sulphuretted hydrogen and marsh
gas.

The three first-named gases are the
principal constituents of the atmosphere,
surrounding the globe, and are found
present in the following average propor-
tion, viz. :

with 2 to 5 vols, carbonic dioxid* in 10,000
vols, of air.

According to R. Angus Smith the
amount of oxygen is :

In the average, 20.96 vols, in 100 vols, of air.
In pure mountain air, 20.98 vols, in 100 vols, of

air.
At the sea shore, 20.999 vols, in 100 vols, of

air.
In streets of populous c ties, 20.87 to 20.90

vols in 100 vols, of air.

The air in sewers and drains contains
much less oxygen, as some of it combines
with the carbon of putrefying organic
matter forming carbonic dioxide. The
amount of nitrogen in the air of sewers
is little different from that in the atmos-
phere which we breathe; but the amount
of carbonic dioxide present is greatly in-
creased.

The lowest amount of oxygen in sewer
air is recorded to be 17.4 vols, in 100
vols, of air ; the amount of carbonic di-
oxide is in the average 2.3 vols, in 100
vols. Sulphuretted hydrogen varies
greatly, but the quantity is generally so

small as not to be easily determined.
Still more difficult is it to find by chemi-
cal analysis the proportion of other gases
of decay.

In well ventilated and well flushed
sewers, Dr. Russell, of Glasgow, found
the following ratio :

20.70 vols, of oxygen in 100 vols, of air.
78.79 vols, of nitrogen in 100 vols, of air.
0.51 vols, of carbonic dioxide in 100 vols, of
air.
No sulphuretted hydrogen in 100 vols, of air.
Traces of ammonia in 100 vols, of air.

Carbonic oxide is present only in excess-
ively minute quantities, and even then it
may have entered the sewer or drain
through leakage of illuminating gas from
gas mains.

In the absence of more satisfactory
methods of analysis, it is usual with
chemists to determine the amount of pol-
lution of the air, or the organic matter
in it, by determining the amount of car-
bonic dioxide present, assuming that
there is a certain fixed proportion be-
tween the amount of carbonic dioxide
and the organic matter.* Thus, Prof.
W. Ripley Nichols records as the average
of many carefully conducted experiments
in Boston, the amount of carbonic diox-
ide in a sewer in that city as follows :

The average of

31 determinations in January, 1878, was 8 7
vols, of C02 in 10,000 vols, of air.

44 determinations in Ft-bruary, 1878, was 8.2
vols, of l02 in 10,000 vols, of air.

47 determinations in March, 1878, was 11.5
vols, of C03 in 10,000 vols, of air.

12 determinations in April, 1878, was 10.7 vols.

of C02 in 10,000 vols, of air.
8 determinations in June, 1878, was 27.5 vols.

of C02 in 10,000 vols of air.
8 determinations in July, 1878, was 21.9 vols.

of C02 in 10,000 vols, of air.

6 determinations in August, 1878, w^as 23.9

vols, of COa in 10,000 vols, of air.

7 determinations in January, 1879, was 8..0

vols, of Co2 in 10,000 vols, of air.
14 determinations in February, 1879, was 11.6

vols, of C02 in 10,000 vols, of air.
20 determinations in March, 1879, was 11.8

vols, of C02 in 10,000 vols, of air.

He remarks : "It appears from these
examinations that in such a sewrer as the

* Such is strictly true only for air fouled by respira -
tion, while it may Dot give accurate results in other
cases.

In regard to this interesting question I must refer
to the Report of Prof. Ira Remsen on the subject of
organic matter in the air, published in the National
Board of Health Bulletin, vol. 2, No. 11.

HOUSE DRAINAGE AND SANITARY PLUMBING.

267

one in Berk, lev street, which, being of
necessity tide-locked, is an example of
the worst type of construction, the air
does not differ from the normal standard
as much as many, no doubt, suppose. In
a general way, as we have seen, there is
a larger amount of variation from nor-
mal air during the warmer season of the

irj but even when the amount of car-
bonic acid was largest, it was only ex-
tremely seldom that sulphuretted hydro-
gen could be detected." .... ""I
think it should be said that the soil pipes
and house drains are much more likely
causes of discomfort and danger than
the sewers."

Hence the importance of a thorough
ventilation of all the soil, waste and
drain pipes in a building.

Are the above-named constituents of
sewer air the origin or cause of the sick-
ness so commonly attributed to the inhal-
ing of sewer gas ?

Although many of the gases named are
poisonous, if inhaled into the system in
large quantities, and may, even if present
in smaller quantity, cause nausea, as-
phyxia, headache, vomiting, etc., none of
them can be said 'to produce any of the
so-called " filth- diseases/' To determine
the exact origin of these is a still unsolved
problem of physiology. While some be-
lieve that the particles of decomposing
organic matter, present in sewer air and
known as " organic vapor " cause disease,
others seek the origin of the latter in mi-
croscopic spores or germs which live and
feed upon such organic vapor and are
capable of reproduction under favorable
conditions, such as presence of putrefy-
ing filth, excess of moisture, heat, lack of
oxv^en, etc.

Whatever theory may be accepted as
true, it is evident that, by preventing the
decay of organic matter within sewers,
drains and soil pipes, or by depriving
these germs (if such be the cause of dis-
ease) of the conditions facilitating their
reproduction, we can best prevent the
outbreak of excremental diseases. In
other words, by completely removing us
speedily as possible all waste matters
from the dwelling by pipes thoroughly
and tightly jointed, and by a sufficient
dilution of the air in these pipes with
oxygen, the danger of infection, arising
from defective drainage and plumbing,
may be reduced to a minimum.

It should be mentioned that some hy-
gienists, notably Dr. Soyka and Dr.
Renk, both assistants of Pettenkofer in
Munich, have lately denied the existence
of any positive proof of a connection be-
tween sewer gas and the spread of epi-
demic diseases — just as Naegeli and Em-
merich doubt the possibility of infection
from drinking water contaminated by
sewage. Dr. Renk considers the exclu-
sion of gases of decay from the interior
of dwellings necessary only so far as they
are offensive to the sense of smell. In
this view, however, I cannot concur; in
regard to "filth-diseases," their causes
and origin, I accept the theory of Dr.
Simon, Parkes and others.

DEFECTIVE AND GOOD PLUMBING WORK.

The unhealthiness of dwelling houses
has been greatly increased by plumbing
work defective in design, materials and
in workmanship, through ignorance, but
often through intention of builders. The
consequence was a growing inclination
with some to abandon all plumbing fix-
tures, to go back to the ill-famed privy in
the backyard, and to follow the practice
of throwing the slops from the kitchen
upon the grounds in the rear yard.

But, cannot this risk be avoided with
careful, conscientious and honest work-
manship, carried out under the strict su-
pervision of an expert ? Is it such a diffi-
cult thing to have a proper and judicious
arrangement of the drainage system ?

I shall endeavor in the following pages
to explain what the elements of a well
devised system of house drainage and
sanitary plumbing are. Much has been
written of late about this subject. It
has been well and thoroughly treated by
able writers, and my paper can hardly
claim much originality or novelty, but
should be taken as the outgrowth of
much study and experience.

The essentials of a perfect system of
house drainage are simple and can be
readily understood by any householder,
when carefully explained. They involve
nothing more than the proper application
of well-known laws of nature ; there is no
mystery, no secrecy about any part of
the work. Any one building a house is
able to secure good drainage and a safe
arrangement of the plumbing work with-
out having to resort to any patented sys-
i tern. The proper way of laying and

268

VAN NOSTRAND'S ENGINEERING MAGAZINE.

trapping drains, of ventilating soil and
waste pipes, etc., cannot, in my judg-
ment, be patented. The plumbing fix-
tures are, of course, mostly patented, as
any useful appliance may be, and in
speaking of these one cannot avoid rec-
ommending patented devices.

The entire sewage of the dwelling may
deliver either into a regular system of
sewers, or else discharge into an open
watercourse; or — in the absence of either
— it may run into a cesspool, be it a
leaching cesspool, or a well-cemented,
tight vault of brickwork ; or finally, into
a flushtank, to be disposed of on the
ground by surface irrigation, or below
the ground by the subsurface irrigation
system.

So far as the arrangement of the inside
plumbing work is concerned, it does not
make any material difference which of
the above systems of getting rid of the
waste- water from habitations is available .*

Under all circumstances the three car-
dinal objects to be fulfilled by a perfect
system of house drainage are :

1. To remove from the inside of the
dwelling as quickly as possible all liquid
and semi-liquid wastes, whether it be the
soapy discharge from wash bowls, bath
tubs'and laundry tubs, or the vegetable
refuse from the scullery sink, the greasy
matter from kitchen and pantry sinks, or
the foul discharges from slop sinks, urin-
als and water closets.

2. To prevent the foul gases originat-
ing from the decomposition of the above
matters in the drain, sewer, cesspool or
flushtank, from returning through the
same channels into our dwellings.

3. To oxidize and render inocuous by
a copious flushing with air the foul gases
due to the possible putrefaction of waste
matters within the house drains, soil and
waste pipes, at the same time properly
protecting all outlets of fixtures from
the entrance of these gases.

DRAINS OUTSIDE OF THE HOUSE.

The house drain is the means for con-
veying the sewage from the dwelling. Its
proper material is a question of great
importance. Outside of the dwell-
ing it should be of vitrified pipe,
circular in shape, which is superior

* It is not intended in this paper to discuss the
merits and faults of these different methods of sew-
age disposal.

to cement pipe. Iron pipe for out-
side drains is preferable in made
ground, or in quicksand, also where
trees are near the line of the drain, and
where the drain must necessarily pass
near a well furnishing water for the
household. Neither brick channels nor
wooden conduits should be used for this
purpose. Only strong, hard, well-burnt,
vitrified pipe, free from cracks or other
defects should be used. Four inch pipes
and those of smaller size are especially
liable to warping, and should be carefully
inspected and selected. The interior of
these pipes should be well-glazed and
smooth throughout ; the pipes should be
impervious, true in section, perfectly
straight, and of a uniform thickness.
Four inch pipes should have a thickness
of J in. to -| in. ; six inch pipes \^ in. to
§ in. ; nine inch pipes should be not less
than j inches thick ; 12 inch pipes should
be 1 inch thick ; fifteen inch pipe 1^ in.,
and eighteen inch pipe should have a
thickness of 1^ inches.

The joints of the pipes should receive
particular attention. The danger arising
from imperfect or leaky joints is twofold,
namely, first, the sewage, by soaking into
the ground, pollutes the soil and endan-
gers the purity of the water supply in
places where nouses are dependent on
wells end cisterns for water. The ground
around and under the house is more and
more subject to contamination, and in
winter time, when there is a strong in-
ward draft into houses from fireplaces
and stoves, the tainted " ground air " is
thus sucked into our very living and
sleeping rooms, often producing severe
illness. The second danger resulting
from leaky joints is equally patent. The
solid matters, carried in suspension in
the pipes, are deprived of a part of their
liquid carrier, and thus tend to accumu-
late and form deposits in the house
drain, which deposits soon undergo de-
composition, and fill the drains and pipes
with noxious gases.

Vitrified pipes are made either with a
socket or hub attached to one end of the
pipe, or with both ends plain. AY hen
socket pipe is used, special grooves
should be cut in the bottom of the trench
for the hub, in order to give the pipe a
solid bearing on its entire length. The
pipes are laid with the socket pointing
upgrade, the plain or spigot end of one

HOUSE DRAINAGE AND SANITARY PLUMBING.

269

pipe being inserted into the socket of In made ground I should recommend the

the next. Spigot and socket ends should use of iron pipes to prevent leaky joints
be concentric. Into the annular space or breakage of pipes. A good Portland
between both a gasket of picked oakum cement will not much increase in volume
is introduced and firmly rammed by a after Betting, and I believe it has beeu
hand iron. The remainder of the space shown that those cements which largely
is then filled with pure cement, or cement increase their volume, often lose their
mixed with an equal volume of sand. No hardness after some time, and would be,
lime should be used with the mortar, therefore, unfit for any use. While I
which should be prepared onl}r in small fully appreciate the advantage of a some-
quantities at a time, to prevent its setting what elastic joint, I do not think that
before use. Particular attention should puddled clay will make as tight a joint as
be given to the bottom part of the joint, seems desirable for drains carrying foul
where the mortar should be pressed into sewage.

it with the lingers. If water accumu- What is known as " Stanford's Im-
lates in the trench, this should be care- ; proved Pipe Joint" has been used exten-
fully removed from the grooves before sively of late in works of house drainage
making the joints, and sufficient earth in England, and its superior merits are
should be thrown into the groove to sup- such as to recommend it for use with us.
port the mortar at the bottom of the I, therefore, introduce a brief descrip-
joint, until it has time to harden. The tion. k'In sewer work in bad or wet
gasket of oakum prevents any cement Irom ground, just where a sound joint is most
projecting into the inside of the drain, ; required, the difficulty of making it is
and renders the use of a rattan and rag, the greatest. What is wanted, therefore,
with which to wipe the inside of joints, is a joint that will entail the least dis-
unnecessary. Where the sockets are in- turbance of the ground, that will not
sufficient in length to permit the use of j necessitate the absolute drying of the
a gasket, it becomes important to clean ; trench bottom, and that will require the
the joints of cement projecting at the ! minimum of time, skill, and labor in mak-
inside, but in this case a better device ing it. These conditions will be fulfilled
than a rattan with rag tied to it is a I in the most complete manner by making
strong handle to which is attached a ' the spigot of one pipe to fit mechanic-
a semi-circular disc of wood, of a some- j ally into the socket of another, as in a
what smaller radius than the radius of bored and turned iron pipe joint. Such

the pipe.

The cylindrical pipe without sockets
is preferred by some. The joints, in this

a mechanical fit cannot be obtained with
stoneware or earthenware pipes, owing
to the difficulty of preserving perfect

case, are made by butting two pipes to- j accuracy of form during the process of
gether, and covering them with rings or burning."

collars of unglazed terra cotta, applying "In the Stanford joint tightness is ob-
cement to the inside of the collar and to tained by casting upon the spigot and in
the ends of the pipes. the socket of each pipe, by means of

Some object to the use of cement for : moulds prepared for the purpose, rings
drain pipe joints, claiming that the stiff- of a cheap and durable material, which,
s of the cement joint after hardening when put together, fit mechanically into
will tend to break the pipes in case of a each other, and by making these rings
slight settling. They also maintain that of a spherical form, a certain amount of
some cements increase considerably in movement or settlement may take place
volume when setting, and tend to burst without destroying the accuracy of the
the sockets. They much prefer a ring of joint. In laying these pipes, therefore,
puddled clay, pressed into the j©int and all that is necessary is to insert the
wiped around it, claiming that clay will spigot of one fairly and firmly into the
make a tight and more elastic joint. But socket of another previously laid, and the
in ordinary cases the settling of drain joint is complete and perfectly water-
pipes may be prevented by providing a tight. A smearing of some kind of
solid foundation of either gravel, sand, grease is frequently found to be of ad-
or concrete, or in very wet ground, vantage."
boards or piles as supports to the pipe. . Half -socket or access-pipes are some-

270

VAN NOSTKAND7S ENGINEERING MAGAZINE.

times useful, where it becomes necessary
often to inspect the house drain. They
should be located close to angles, bends,
junction branches, running traps, &c.
They are not much used in this country,
owing, probably, to the fact that, should
the main drain run over one-half full,
sewage may leak out through the access-
pipes into the soil.

Care should be taken to lay the pipes
on a firm bed of sand or gravel, and if
this is not available, a concrete base
should be provided in the trench. The
pipes should be laid in straight lines, all
changes of direction should be effected
by curves of as large a radius as possi-
ble, formed of bent pipes. All branches
should join the main under an acute an-
gle, by special Y pieces, for a right-an-
gled junction (by a T branch) tends to
form eddies and consequently deposits
in the main drain.

In laying drains, care should be taken
to avoid, as much as possible, trees.
The roots of these are frequently found
to penetrate and often choke the pipes,
and are certainly a dangerous obstruc-
tion to the flow in the drain. If the
line of the drain must necessarily pass
near trees, the use of iron pipes is re-
commended. The coating of the pipes
with coal tar on their outside, the use of
asphaltum for joints, and sometimes the
surrounding of the drain with a strong
layer of concrete are said to be effectual
protections against roots of trees.

I now must speak of the grade of the
drain, as this is a matter of prime im-
portance. Upon the inclination of a
pipe depends the velocity of the water
flowing through it. If this velocity
should be insufficient, deposits will oc-
cur, and the drain will in time become
choked. Pipes of 4 inches diameter
should have a velocity of flow of from 3
to 4J- ft. per second ; those of 6 and 9
inches diameter should have a velocity
of not less than 2 £ to 3 ft. A velocity
of 2 ft. per second should be consid-
ered the minimum allowable in house
drains. As a general rule the inclination
of a house drain should be as great as
attainable, and must be, wherever local
conditions will permit, continuous. It
is not unfrequently found by uncover-
ing old drains that, in order to save
digging, they are laid very flat, often per-
fectly level, from the point where they

leave the house to nearly their junction
with the sewer, at which place they are
turned with a steep pitch downwards,
and often enter the sewer at its crown.
By distributing the whole available fall
over the total length of the drain a
much better grade would have been se-
cured.

In order to lay a drain with a true
grade, especially where the fall is little,
a level should be used. The elevation
of bottom of pipe, where it leaves the
house — at a depth of not less than 3
feet in the New England States, as a
protection against frost — should be as-
certained, as well as the elevation of
the junction with the sewer (or else in-
let to cesspool or flush tank). A profile
of the ground along the line of the drain
should also be determined by levelling.
Thus, the proper available fall can be de-
termined, with a little additional trouble,
it is true, which, however, will be well
repaid by securing a much better quality
of the work.

A fall of from 1 in 40 to 1 in 60 is de-
sirable for pipes of 4 or 6 inches diam-
eter, but this cannot always be had. I
would consider a grade of 1 in 100 as
the least to be given to house drains, in
order to keep them self-cleansing. When
laid with such fall and running full or
half-full, a six-inch drain has a velocity
of 3J feet, a four-inch drain a velocity of
nearly 3 feet, which is sufficient to carry
along such suspended matters as only
ought to enter a house drain. Where
the available fall is less than 1 in 100,
special flushing apparatus, such as Field's
flush tank, McFarland's tilting tank, or
Shone's hydraulic syphon ejector should
be used.

I have thus fully explained the right
method of laying drain pipes, because,
even with the best plumbing inside of
the house, it is of the greatest importance
to have -the outside drains of good qual-
ity, properly laid, and properly jointed.

The next question to be considered is :
What is the proper size for house
drains f

This will, of course, depend to some
extent upon the grade of the drain, the
size of the house and number of its oc-
cupants, the amount of water used per
head per day, and finally, unless the rain
falling upon the roof is stored in a cis-
tern, upon the amount of rainfall to be

HOUSE DRAINAGE AXI) SAXITAKV PLUMBING.

271

earned off in a certain time. This rain liver it into the same channel, which car-

a most beneficial scourer for drains, ries away the fonl wastes of the habita-

and unless the sewage of the dwelling is tion. Even with this double purpose in

to be disposed of by irrigation, or the view the house drain need not be very

^ S

O *

83 o

^ 03

SO ^

|-1 &H

« |
O PS

w
S 5

Q
M

O fc

O E-1

O <

B 5

sewers of the town built according to large, and the closer its size is propor-
the "separate system, " which excludes tioned to the volume of water it must
the rain-fall from the channels carrying ; carry the more self-cleansing will it be.
sewage, I should strongly advise to de- i To illustrate the advantage gained by

272

VAN NOSTRAND'S ENGINEERING MAGAZINE.

reducing the size of drains as much as
possible, or in other words by concentrat-
ing the sewage flowing through it, I have
constructed the diagram, Fig. 1, which
represents for different depths of flow in
the same pipe the change of velocity. It
is evident that the velocity in a pipe will
greatly diminish as the depth of the
stream flowing through it diminishes.
The diagram shows that the velocity is
the same for drains running full or half
full ; it also shows that the maximum
velocity of flow occurs not when the
sewer is running full, but when the
depth of flow is about .813 of its diam-
eter. The maximum velocity is about 11
per cent, greater that that of a pipe run-
ning full or half full. The maximum dis-
charge, however, does not coincide with
the maximum velocity. The discharge is
a maximum when the depth of flow is
about .95 of the diameter. At a depth
of flow of one fourth of the diameter
the velocity is only about 77 per cent.
of that when running full or half full,
and for lesser depths of flow it dimin-
ishes rapidly.

For an ordinary city dwelling a drain
four inches in diameter is ample, even in-
cluding all the rain-fall. For a larger
lot and residence a six-inch drain is all
that is needed, even if the fall should be
only 1 in 100. As a general rule, house
drains have been constructed of too large
a diameter, and one often meets with the
objection that a four-inch pipe will clog up
with grease in a short time, or will be
obstructed by solid substances. To this,
I answer, that in regard to grease the
only safe way, where it is allowed to
waste, or in case of large boarding-
houses and hotels, is to keep it altogether
out of the drain (which can be easily
accomplished by a suitable grease trap).
Grease congealing in a drain is sure to
clog it, no matter how large it is made.
The stoppage would be only a question
of time, and nothing could be gained by
postponing this inevitable result. In
regard to obstructions by solid matters,
I may assert that nothing which passes
through the strainer of a sink or from
the water-closet bowl can possibly ob-
struct the drain. What may enter
through carelessness of servants, or of
the householder, such as " sand, shavings,
sticks, coal, bones, garbage, bottles,
spoons, knives, forks, apples, potatoes,

hay, shirts, towels, stockings, floor-
cloths, broken crockery, etc.,'' to quote
from Mr. J. Herbert Shedd's Report on
the Sewerage of Providence, cannot
rightfully be expected to be carried away
in a, drain. To guard against such ob-
structions, the drain should be made
accessible, especially near bends, junc-
tions and the main trap.

The following useful table, calculated
by Eobt. Moore, Esq., C.E., f rom Weis-
bach's formula for flow of water through
open culverts, gives the size and velocity
in house drains, laid at different inclina-
tions, and for various sizes of lots, the
rain-fall being 2 inches per hour, and the
pipes running f full. It should be said
that the smallest sizes of the table (below
3 or 4 inches diameter) are given only
for the sake of completeness, and not as
sizes to be recommended for actual use.

Take, for example, an ordinary city lot
of 25x150 ft. = .0861 acres. The rain-
fall to be provided for may be 2 inches
per hour. Though such storms are not
frequent, provision should be made for
them in the calculation of the size of
house drains, as the rain falling on roofs
and on paved yards reaches the drain
very soon after having fallen. A rainfall
of 1 inch per hour per acre very nearly
yields 1 cubic foot per second, therefore
2 inches per hour give 2 cub. ft. per sec.
per acre. The number of cubic feet of
rain from the above lot is therefore .0861
X 2 = .1722 cub. ft. per second or 60 X
.1722 = 10.332 cub. ft. per minute.

We further assume 6 persons to the
house, and 75 gallons per head per diem,
which is a very liberal allowance. The
waste water of the house is therefore 6
X 75 = 450 gallons per day. If one-
half of this amount is estimated to run
off in 8 hours, the maximum per hour
would be about 28 gallons or .0624 cub.
ft. per minute. This quantity is. so in-
significant compared with the rainfall
that we may safely neglect it.

Should the drain be allowed to run
three-quarters full, and have a fall of 1
in 100, a diameter of 3f inches would
suffice, according to above table.

As a second example, I shall take a
large lot, say 80 X 150 ft. = .2755 acres.
The quantity of rain to be discharged
will be, under the same suppositions as
above, 2 X 60 X .2755 acres=33.06 cub.
ft. per minute. For a drain, running f

HOUSE DRAINAGE AND S ANITA KY PLUMBING.

278

Table of Diameters of House Drains

With various Grades, and for Lots of different sizes, capable of discharging 2 inches of
tain per hour when running three-fourths full.

Calculated by Robert Moore, C. E., St. Louis, Mo.

Dimen-
sions of No. of

lot in acrea

feet

Fall,
. 1 per 100.

Fall,
2 per 100.

» T—
-*<

Fall,
3 per 100.

Fall,
4 per 100.

Fall,

5 per 100.

30x150 0J

Velocity 2.69 3.16
Diam. Indus 34 3£

3.54
3

3.87

4.17
2£

4.68

5.11
2\

95x160 0.0861

Velocity 2.81 3.30
Diam. Inches 3f 3$

3.71

3£

4.05
3i

4.36
3

4.89

2£

5.35

30x150 0.1033

Velocity 2.91 3.43
Diam. Inch 4 3f

3.84
• 31

> 4.20
3f

4.33

4.52
3i

5.07
3

5.54
3

35x150 0.1205

Velocity 3.00 3.53
Diam. Inches 4£ 4

3.96
3f

4.66

5.23
3±

5.72
31

40x150 0.1377

Velocity

Diam. inches

3.09

3.59
4*

4.07
3|

4.45
3f

4.79
3|

4.90

5.37

5.87
3±

45x150 0.1550

Velocity

Diam. Inches

3.16
4*

3.71

4.17

4.56
4

5.45
34

6.01
31

50x150 0.1722

Velocity

Diam. Inches

3.23 3.79
5 4£

4.26
4*

4.65 1 5.01
4i 4

5.62
35

6.14
3f

60x150 0.2066 ^m.^nches *\ ^

4.41
4f

4.88 5.19
4| 4i

5.83
4

6.37
31

70x150 0.2410 ™tches

3.45 4.06
6f 5±

4.55 4.98 5.35

41 | 4| ^

6.01
4i

6.57

4£

80x150 0.2755 K£?fo£

3.54 4.17
6 5*

4.68 5.11

5± ' 5

5.50

6.17 6.75

4i : 4f

90x150 0.3099 punches

3.63 4.27
6* 5f

4.79 5.23
51 i 5i

5.63
5

6 32 6.91
4f , 41

100x150 0.3443 ^'inches

3.71 4.36
61 6

4.89
51,

5.11

5.35

5.75
5i

6.45 7.05
5 4f

125x150 0.4304 ™£fcfo

3.87
7*

4.56

6.1

4.73
7*

5.59 6.01
6 5f

6.75
5s-

7.38
5i

150x150 0.5165 J^JlLL''
Diam. Inches

4 02

5 30
6f

5.80 6.24
.6| 6i

7.00

7.65

175x150 0.6036 X^fT'
Diam. Inches

4.14 4.87
8£ 71

5.47 5.99 6.45
7* 6£ 6}

7 22
6i

7.89
6

200x150 0.6887 Velocity. . . . .
Diam. Inches

4.26 5.06

8£ j 8

5.62 6.14 6.61

7^ . 7i 6*

7.41

8.10

full, the- table gives the necessary di-
ameter =5J inches.

For a convenient graphical exhibit of
the relation between inclination, size, ve-
locity and discharge of drains and sewers

see the author's M Diagram for Sewer
Calculations," 1881, N. Y.

The foregoing explanations have, I be-
lieve, sufficiently proved that no house
drain needs to be larger than six inches

274

VAN nostrand's engineering magazine.

under ordinary circumstances, while in
most cases a 4-inch pipe will fully answer
the purpose. Any increase of size would
tend to be a detriment rather than a
benefit.

DRAINS INSIDE OF THE HOUSE.

The earthenware drain should end at
about 5 to 10 ft. outside of the founda-
tion walls of the house. From this
point towards the inside of the house
the drain should be of iron. The joint
between iron drain and earthenware pipe
should be made with pure hydraulic
cement. Where the iron pipe passes
through the wall, a relieving arch should
be built over it. Settlement of walls
often occurs, and is liable to crack the
pipe or even break it, unless the above
provision is carried out. It is quite
evident that, under no circumstances
whatever, this part of the house drain
should consist of vitrified pipe.

Important as it is to have the drains
outside of the house free from sediment
or leakage, it is still more so to have all
the pipe joints inside of the dwelling
perfectly air and water ti^ht, for if any
defect should exist here, sewer gas will
leak into the cellar and pervade the whole
house. For this reason we sometimes
find the cardinal rule laid down that no
drains should run under a house, but
should be taken outside of it as soon as
possible. This is not practicable, as a
general rule, in the case of narrow city
Jots. Fortunately, however, we can, with
perfect safety, run the drains across the
basement or cellar floor of a dwelling,
provided we choose the only safe ma-
terial, i. e. iron pipes. A good mechanic
is able to make with these a perfectly air
and water tight joint.

The best course of the iron drains in
the house is along the ceiling of the
cellar, or along one of the foundation
walls. In other words, wherever prac-
ticable, the iron drain ought to be kept
in sight, in order to enable anybody to
detect a leaky joint at occasional inspec-
tions. Sometimes fixtures located in the
cellar, such as servants' water closets,
laundry tubs or sinks, make it necessary
to lay the iron drain below the cellar
floor. In this case it should be laid with
proper fall in a trench, the sides of which
are walled with brick work, and the base

of which should consist of a layer of
from 4 to 6 inches of concrete, thoroughly
rammed and properly graded. The
trench should be made accessible by
closing it with movable covers of iron or
wood.

If the drain is carried in sight, I would
much prefer supporting it by strong iron
hooks from the cellar wall, or by brick
piers, where the ground is solid, and not
liable to " settle," instead of suspending
it by iron hangers from the main joists
of the floor above. For, with the latter
arrangement, a slight lowering or bend-
ing of the beams supporting the iron
drain, would tend to loosen the joint be-
tween water-closet trap and soil pipe, as
the latter is rigidly connected with the
drain, thus creating a source of danger
from leakage of sewer gas.

As regards the proper inclination of
iron drains in the cellar, the rules given
for the outside drains should be ob-
served.

The principles stated for the size of
the outside drain apply with equal force
to the inside drain. If no leaders enter
the drain at its upper end or along its
course through the house, a 4-inch pipe
is ample for any ordinary sized dwelling ;
a 6-inch drain is very seldom required.

As a good precaution for repairs or
cases of obstructions of the drain, I
would recommend the practice of many
plumbers, which consists in inserting at
distances of about 10 or 20 feet along
the course of the iron drain Y branches,
the ends of the branches being closed by
a brass thimble, caulked into the hub of
the Y, and closed by a trap screw. By
opening these and inserting a proper
cleaning tool, occasional obstructions by
introduction of foreign matters are
easily removed.

The course of the main drain in cellar
should be as straight as possible. All
changes of direction should be made by
iron bends. All junctions with the main
drain should be made by Y branches, in
order to join the flow of both pipes
without causing eddies ; no right-angled
junction should be made in any hori-
zontal or inclined pipe.

SOIL AND WASTE PIPES.

Into the iron drain the vertical soil
and waste pipes enter by means of either

BOUSE DRAINAGE AM) SAMTAllV PLUMBING.

275

quarter bends or by a Y branch with as
eighth bend.*

The best material for soil and waste
pipes is east iron. All east iron pipes
used in house drainage should be thor-
oughly sound, of a uniform thickness
throughout, and must allow of ready
cutting without splitting. The inisde
should be truly cylindrical and of smooth
finish. The thickness of ordinary (so
called light) soil pipe is about £ of
an inch for 2, 3 and 4-inch pipes, and
i A of an inch for 5 and G inch pipe.
For all large public or private buildings
I should always insist upon the use of
extra heavy soil pipe, which is about
double as thick as the ordinary pipe.
The weights of extra heavy pipe are
about as follows :

2 inch pipe,

3 inch pipe,

4 inch pipe,

5 inch pipe,

6 inch pipe,

5£ lbs. per foot.
4 lbs,

, per foot.

16 ids. per foot.

17 lbs. per foot.
20 lbs. per foot.

Great care should be exercised by
plumbers, architects, plumbing inspect-
ors and sanitary engineers in regard to
the uniform thickness of iron soil pipe.
The writer has lately seen specimens of
extra heavy soil pipe where the pipe was
almost as thin as a knife-blade on one
side, while it had far more than the re-
quired thickness on the other side, the

* As regards the exact meaning of the terms drain
pipe, soil pipe, and waste pipe, I quote the following
elear explanation from the " Sanitary Engineer," Vol.
4: "The drainage system of a house, including the
pipes or channels of any kind connecting it with the
sewer or cesspool, may be divided into two parts-
first, that part whjch is chiefly outside the house walls,
and second, that which is generally inside the house.
The first is called the howe drain, or simply drain,
and conveys the whole body of wastes from the
house, including both the discharges from water-
closets and urinals, and from baths, basins, sinks, &c,
to the sewer or cesspool. The drain is practically
horizontal, and may be considered as terminating
either at the house wall, or at the most remote point
at which it receives the pipes from any fixtures. The
word drain is, however, also used in another sense as
distinguished from sewer. It then means the pipe or
channel which conveys only rain or ground water, as
distinguished from sewage. An example of this kind
of drain is the separate system of pipes, used to con-
vey only rain water in some towns and the tile pipe
commonly employed in draining wet lands.

"That part of the house drainage system which is
generally inside the house, including the pipes from
the various fixtures, is made up of soil pipes and waste
pipes. Soil pipes are those pipes which receive hum an
eorereta from water closets and urinals, and they are
still called soil pipes, even if they also receive the
waste water from baths, basins, &c. On the other
hand, waste pipes are those which receive only the
waste water from these latter, but not the discharge
from water closets and urinals. The waste pipes of a
house may either enter the house rf/Ywundependently,
or join the soil pive first and discharge their contents
through it into the drain. As distinguished from the
drain the soil pipes and waste pipes, at least for the
longer lengths, are generally vertical.''

weight being as specified. Measuring

the thickness of iron drain pipes 1>\ a

pair of calipers should be recommended,
but I am not aware that it is done at all

now.

Iron soil pipe, the inside of which
has been made smooth by dipping the
pipe into a hot solution of coal-tar pitch,
is superior to ordinary iron pipe. This
coating, when applied to the ontsid
the pipe, forms a good preventive against
rust or corrosion, and is better than
any paint applied to the iron. Where
economy is no object, the enamelled
pipe may be used, which has a very
smooth inside surface, thus securing to
well-flushed soil pipes the greatest pos-
sible cleanliness. Whether iron pipes
are coated with coal tar pitch or en-
amelled, it is necessary, before applying
either of these protective coats, care-
fully to test each pipe for defects, sand
holes or cracks, by the hammer test.
The coating may effectually cover these
defects and render detection difficult.

Iron pipes are manufactured in lengths
of 5 feet, writh hub and spigot end. or
else with double hub.

The iron works manufacture not only
straight soil pipe, but a large number of
fittings, such as quarter bends, eighth
bends, sixth bends, sixteenth bends. T
branches, Y branches, double Y branches,
half Y branches, offsets, single and double
hubs, increasers, reducers, &c, to en-
able the plumber to make all possible
connections and lines with iron pipe.

In England lead pipe is preferred for
soil pipes. According to one of the
best English authorities on plumbing*
the advantages claimed for lead pipe
are briefly as follows:

1. It is smoother, cleaner, not so cor-
rosive ; more durable.

2. It can be bent to suit any position ;
it is more compact.

3. Its joints are more to be depended
upon than iron pipe joints.

■A. Urine, being very corrosive, acts
more on iron than on lead.

5. Iron pipe rusts on the outside,
and painting iron pipes, to prevent it,
is expensive, and is generally not done
thoroughly at the back of the pipe.

6. Lead branch wastes or traps cannot
easily be joined to iron pipe.

* S. Stephens Hellyer, " The Plumber and Sanitary
houses," 2d edition.

276

van nosteand's engineering magazine.

7. Iron pipe does not allow caulking
joints with lead, therefore cement is used
for the joint.

From all this I disagree, for :

1. Tarred or enamelled iron pipe is
fully as smooth as lead pipe, and the
iron pipe is thereby well protected from
corrosion.

2. The above enumerated variety of
special fittings enables the plumber
readily to adapt his iron pipe to almost
any position; moreover I do not see
why iron pipe should take up a great
deal more room than lead pipe of same
bore.

3. Well caulked joints of heavy iron
pipes are just as sound and trustworthy
as wiped joints in lead pipes, and any
good mechanic is able to make them.

4. Urine does not corrode an iron soil
pipe, protected by a coal-tar pitch so
lution or by enamel, more than a lead
pipe.

5. The outside of iron pipe can be
efficiently protected from rusting by
paint, coal-tar pitch or enamel.

0. Lead cannot be caulked into iron,
but a good plumber always solders a
brass ferrule by a wiped joint to the lead
pipe (or trap), and caulks the brass fer-
rule into the hub of the iron pipe.

7. Any one who will take the trouble
carefully to examine the joints of iron
pipe, made by an honest and conscien-
tious plumber, will readily admit the pos-
sibility of making tight joints with iron
pipe. Only iron pipe of a sufficient
strength to withstand the knocking oc-
casioned by caulking the lead is used in
American plumbing.

But, while iron pipe is fully equal in
all the above respects to lead, it has
great advantages over it. " Lead soil
pipes are very heavy, and, therefore,
liable to sag and split open, to have
holes eaten into them by rats, and have
nails driven into them by carpenters, and
also to corrode, and they require much
greater skill to put up, and involve more
expense ; therefore the statements of
Hellyer prove nothing, although they
demonstrate the absurdity of bricking
soil pipes into a wall, and the necessity
of so placing them that they are at all
times readily accessible for inspection ;
and also prove what few people seem to
realize, that the drainage system of a

house requires periodical testing and
inspection just as much as a steam boiler
or piece of machinery." *

Pipes of wrought-iron, coated with
coal-tar pitch, have been lately used for
soil pipes, notably in the Durham system
of house drainage. I am not prepared
to say whether or not such pipes last as
long as cast-iron pipes protected with
the same coating.

Soil pipes should not, as a rule, be
larger than four inches inside diameter :
this size will answer for half a dozen or
more water closets on one vertical stack of
pipe. From a late account of the sew-
erage of the city of Pullman, near Chi-
cago, I learn that several hundred soil
pipes of 3-inch bore were used in the
houses, and " in the case of three-story
flats, one pipe frequently has six closets
connected to it." Very few instances of
stoppage occurred, and these were al-
ways " due to obstructions that got in
during construction, and never to the
use of a small-sized pipe." Such a re-
duction of the size of soil pipes will un-
doubtedly increase the danger of "siphon-
age of traps," and for this reason it is
hardly safe to use soil pipes smaller than
four inches inside diameter.

Waste pipes of iron should be 1^ or 2
inches in diameter. This is ample for
the waste water of one or more bath
tubs, and a large number of wash bowls.

I may here remark that, contrary to
the generally entertained opinion, a near-
ly horizontal or inclined pipe can be kept
clean by flushing much easier than a ver-
tical pipe. The flashing water in this
latter case soon assumes a whirling mo-
tion, and the scattered drops fall down-
ward without exerting much scouring
action upon the interior of the pipe.
Hence the importance of having the in-
side of soil and waste pipes as smooth
as possible to prevent solid matters
from adhering to the sides, where hard-
ly any amount of flushing will take them
off.

The arrangement of soil and waste
pipes should be as direct as possible.
It is desirable that each vertical stack
should extend from cellar to roof in a
straight line. In planning the plumbing
for a dwelling too much care cannot be
taken to secure such an arrangement.

* See articles on "Plumbing Practice," in the Sani-
tary Engineer, vol. 4.

HOUSE DRAINAGE AM) SANITAKY PLUMBING.

277

Every offset, every bend in the pipe
forms an obstruction to its proper flush-
ing, with both water and air. Horizontal
1 pipes are especially objectionable;
the water closets, baths, bowls and sinks
should always be located in groups, and
as near to their respective pipes as pos-
sible.

It is desirable to run soil pipes and
waste pipes in Bight, so that they maybe
accessible. I decidedly condemn the
usual plan of architects of building re-
cesses or niches in the walls for pipes.
The difficulty of caulking the back part
of pipe joints in this position is very
great. Where objection exists to having
the pipes in sight, they should be boxed
up, but I would always insist upon hav
ing the cover fastened by screws, which
can be easily removed, and not by nails.

Iron soil and waste pipes should be
supported at distances of not over five
feet by strong iron hangers or hooks.

Branch pipes should enter the vertical
stack by means of a Y or half Y branch,
wherever possible ; a right-angled junc-
tion, by a T branch, is not so objectiona
ble here as in the case of horizontal or
inclined pipes.

In badly drained houses, with cheap
plumbing work, it is not uncommon to
find the joints of pipes made only with
sand and paper, or with putty, mortar,
cement, sulphur and pitch and red lead,
or other material. All of these joints
are worthless, and therefore extremely
objectionable.

Joints of iron pipe should be made by
first inserting a little picked oakum into
the socket, care being taken that no part l
of this gasket enters the pipe. The i
oakum prevents the molten lead from !
running into the pipe, where it might j
form an obstruction to the flow. Molten j
lead is then poured into the hub, enough
quite to fill it. As lead shrinks in cool-
ing, it must afterwards be carefully ham-
mered with a special caulking tool, thus
filling the space between spigot and hub, j
so as to make a perfectly gas and water ;
tight joint. In order to be able, at all
times, to inspect the joints, it is a good
practice to leave the caulked lead without
a cover of paint, cement or putty, the
marks of the caulking tool being thus left
exposed to view.

A tight joint can also be made with a
mixture of sal ammoniac, iron filings and

sulphur. Such " rust joints,'' however,
are not much used for soil pipes.

Where wrought-iron is used for soil
and waste pipes, the joints are BCrew
joints, ami can be made tight as in steam
fitting work.

When all the iron piping in the house
is completed, the tightness of the joints
should be thoroughly tested, before con-
necting the fixtures. The test which is
mostly used, is the "water pressure test."
The end of the iron pipe outside of the
foundation walls is tightly closed byawood-
en plug, or better, a disc of india rub-
ber, which can be squeezed between two
iron discs. All branches of soil pipes
and waste pipes are similarly closed. The
pipes are then filled with water, which
must stand in them for some time. If
the subsequent inspection shows a lower-
ing of the water level, there must be a
leak at some joint, or else some defect
exists in the iron piping. Of course the
leak must be found and repaired, and the
test should then be repeated, until all
joints are water and air tight.

An equally reliable pressure test is
made by using a force pump and a ma-
nometer.

For occasional inspections of old
plumbing work, and in making sanitary
examinations of houses the "peppermint"
and the " smoke test " become useful.
The peppermint test is thus described:
" When called on to detect a leak in the
soil pipe of a house, the plumber goes at
once to the roof, if the soil pipe be car-
ried above the roof; if not, he goes to
uppermost water closet, and pours into
one or the other something like an ounce
of peppermint, and follows it up with
enough water to insure its being carried
the full length of the soil pipe. (The
top of soil pipe should be closed, in or-
der to prevent the oil from escaping into
the outside air.) "Another man then
traces the soil pipe from the bottom,
throughout its course; knowing that if
there is any crevice through which sewer
gas can enter, the pungent odor of the
volatile essential oil will be readily per-
ceptible even in the presence of odors of
a baser kind. Great care must be taken
not to carry the peppermint about the
house, otherwise the smell cannot be
traced to the drains."

Captain Douglas Galton describes an-
other test thus : " To test the drains the

278

VAN NOSTEAND7S ENGINEERING MAGAZINE.

fumes of ether or of sulphur may be
used. If ether is poured down a soil
pipe the fumes will be perceptible in the
house at any leaks in the soil pipe or
failures in the traps. Sulphur fumes may
be applied by putting into an opening
made in the lowest part of the drain an
iron pan containing a few live coals, and
throwing one or more handfuls of sulphur
upon the coals, and closing up the open-
ing to the drain with clay or otherwise.
The fumes will soon be very perceptible
at any leaks or rat holes in the soil pipe,
drains or traps."

The connections between fixtures and
the soil or waste pipes are made with
lead pipe, which can easily be handled,
and may be bent and cut to suit all pos-
sible positions, and requires but few
joints. It is manufactured in long coils,
of all sizes and of any desired thickness.
In good plumbing work only heavy lead
pipe should be used to prevent its being
quickly destroyed by the corrosive action
of sewer gas. It is desirable that lead
pipe should be used as little as possible
in concealed places, as it may be gnawed
by rats or split by nails thuough careless-
ness of carpenters.

It is not uncommon to find vertical
waste pipes of lead, as these are easily
placed inside of a partition and covered
with plaster. But this cannot be regard-
e 1 as good practice ; iron for waste pipes
is decidedly to be preferred.

Vertical lines of lead pipe should be
fastened to boards by soldering hard
metal tacks to the pipe and screwing
the flanges of the tacks to the board.
Horizontal lines should be continuous-
ly supported on boards between joists.
Lead pipes are mostly joined by what is
called a "wiped joint." The end of one
pipe is flanged out so as to form a cup,
into which the other pipe, the end of
which should previously be sharpened, is
introduced. Hot solder is then applied
to the joint, and wiped around it so as
to form an oval lump.

Where lead pipes are joined to iron
pipe, the connection should be effected by
means of a brass ferrule of the same bore
as the lead pipe, and soldered to it, wher-
ever space allows, by a wiped joint. The
ferrule is introduced into the hub of the
iron pipe, and caulked tightly with a
gasket of oakum and molten lead.

The size of lead waste pipes should be

as small as is consistent with the office
which they have to perform. Wastes for
bath tubs or laundry trays should be
sufficiently large to empty these vessels
in a short time.

The following sizes of waste pipes for
fixtures should be recommended :

For wash basins 134 inches diameter.

For wash basin overflows .±34

For bath wastes \%

For bath overflows 114

For wash tub wastes .\%

For kitchen sink wastes . .1^|
For pantry sink wastes . . .134
For slop sinks 13^to2 "

Local conditions will, in some cases,
demand a deviation from these sizes.

On Weyrauch's Formulas for the
Strength of Materials. — By A. Brull.
— Admitting the value of "Wohler's ex-
periments, it was best to retain the prim-
itive limit of elasticity as the standard of
working resistance. It had been shown
by experiment that under certain condi-
tions neither limit of elasticity nor break-
ing strength preserved their primitive
values. But in working practice such
conditions seldom existed, and the former
might then safely be held to possess a
definite and constant value. Wohler had,
in many instances, broken specimens of
iron and steel by alternation of equal op-
posite stresses below the elastic limit ; but
the stress was very rapidly reapplied,
though not with shock or absolute sud-
denness. It was well known that the
minimum intensity of a suddenly applied
load, required to produce a given elonga-
tion was half that of the corresponding
statical stress, when the given elongation
was below the elastic limit. From this
it was inferred by Lippold, that the sud-
den application of stress below the limit
of elasticity, but exceeding half its value,
produced some permanent set, and at
each repetition of the same stress a cer-
tain amount of work was spent in pro-
ducing that result ; rupture following
when the total work so expended attained
a sufficient value. The complex methods
of calculation of Dr. Weyrauch, could
not replace that based on the limit of
elasticity until, for different qualities of
material, prolonged experiment had fur-
nished more definite values for the new
coefficients. — Resume de la Societe des
Ingenieurs Civils, Paris.

THE DYKES <>F tSLE DE RE.

271)

THE DIKES. OF ISLE DE RE.

Translated from Annates des Ponts et Chausees for Van Nostrand's En<.inkkking Mauazine.

A great portion of the Isle of Re, es-
pecially the west-north-west part, is be-
low high-weter mark and is protected
from the sea by low dunes and by dykes
whose total length is more than 9 kilo-
meters (5.6 miles).

As these dykes preserve a territory oc-
cupied by a considerable population, they
are regarded as works of great import-
ance, and the continual care bestowed
upon them is fully justified.

Before 1789 they were maintained by
contributions levied upon those directly
interested, and by the budget of the
province of Aunis, for which the island
was considered a sort of breakwater. The
State also aided in the maintenance by a
relief fund.

After the Revolution the Slate as-
sumed entire control of the dikes, and
they are now regarded as works of
generl interest.

Formerly the outer slopes were cov-
ered with loose stones resting upon clay,
but as this construction offered but poor
resistance to the sea the breaks were nu-
merous and were repaired only at con-
siderable expense. Then the method of
fascines and stakes was tried, but soon
abandoned on account of the rapid de-
cay. After this a method in imitation of
the plan practised in Flanders was tried,
and a slope of dry masonry was laid
upon a bed of broken stone 16 to 20
inches in thickness. This construction
held for a time, but when a breach was
once made by waves in stormy weather
it enlarged with frightful rapidity.

It was finally decided in 1846 to cover
the slope with masonry laid in hydraulic
cement with a total thickness of two feet ;
an outer course of one foot thickness
being rough ashlar, and the under course
of equal thickness being rubble. This
system succeeded perfectly.

The slope of the masonry is for the
most part 2 to 1. The inner face of the
dike or levee has a slope of 1£ to 1. It
is covered with clay and planted with
Tamarisk which grows readily on the
island. The dikes have a width at the

top varying according to circumstances,
but is generally two meters, and raised
to a height of three meters above the
highest tides. This height would be in-
sufficient during great storms to prevent
the waves from breaking over the work
to the injury of neighboring plantations.
The dike is therefore surmounted with a
parapet two feet high (om. 6), so formed
thatwith the outer slope the cross section
is a parabola with a horizontal axis. By
this construction a lower height of wall
suffices to resist the waves.

The masonry generally rests on the
limestone rock which underlies the whole
surface of the island. When the rock is
too low for this purpose, the work is
made to rest on a tolerably firm sub-
stratum of earth which is found below
the sand. It is rarely necessary to go
deeper than three or four meters for this
purpose.

It was at first thought necessary to
protect the foot of the wall, where it was
not founded on rock, by a system of sheet
piling. It was not however required.
In calm weather there are no waves to
cause damage, and in stormy weather the
retreating wave sliding down the ma-
sonry slope meets another wave so that
the stonework receives the shock, and
the sand at the foot is not disturbed,

The dikes of Petit Pres (Fig. 1) and
of Maison Neuve (Fig. 2) represent the
different forms employed in Isle de
Re.

The cost varies with the price of ma-
terial, but averages for the type of Fig. 1
100 francs per meter or 18 dollars per
lineal yard, and for the other variety 150
francs per meter or 27 dollars per yard.
This estimate does not include cost of
land, which is generally government
property.

The products of the sea are not of
much benefit to the inhabitants of the
island, but it is nevertheless necessary to
construct at convenient distances ap-
proaches to the shore, which may be used
as roadways for the transportation of
fish or of such materials as are used as

280

VAN NOSTRANrTS ENGINEERING MAGAZINE.

fertilizers of the land. These roadways
increase somewhat the sort of the dike.

Along the greater part of the coast of
the island there is a body of sand carried
along by the littoral currents. The plan
of causing a deposit by means of groynes
was tried, but soon abandoned. Sand

gerous points. The present type of
dike has successfully resisted the sea for
twenty years. The older form is occa-
sionally broken through in places never
before disturbed. In restoring such
portions the modern type is always made
to replace the ancient.

A — A.

[iiniiiii

Scale of Metres

was deposited on the up-stream side, but
the shore was eroded to a coresponding
extent on the other. Only where the
shore was naturally very solid could the
plan be profitably adopted.

These dikes are, as already stated, 9
kilometers in length, and being of vital
importance to the country, they are the
object of continuous and careful surveil-
lance.

A brigade of skilful cantonniers are in
constant attendance to repair at once
any breach in the wall, and who are re-
quired especially to act with promptness
in mending the breaks occasioned by
storms. It is necessary to be carefully
guarded with solid materials at all dan-

The annual cost of the maintenance of
the dikes of the Isle de Ke is 25,000 to
26,000 francs ($5,000 to $5,200). This
amount would quite cover aU sorts of
repairs and maintenance if they were
throughout of modern construction.

The electrical perturbations were sofj fre-
quent on the French lines from April 16 to
20, that measures had to be taken by the
Minister of Postal Telegraphy to meet this con-
tingency. The electrical equilibrium was re-
stored on the 21st. These electrical perturba-
tions were noticed on the telegraphic lines of
Germany, Belgium, and Italy, and of England,
according to the notice which was published
by the French Administration in the official
paper of the Government. — Nature.

TIIE CONSERVANCY OF RIVERS.

281

THE CONSERVANCY OF RIVERS : THE EASTERN MIDLAND

DISTRICT OF ENGLAND.

By WILLIAM HENRY WHEELER, M. Inst. C.E.
Proceedings of the Institution of Civil Engineers.

The conservancy of the rivers of this
country is a question continually grow-
ing in importance. It is one which
must before long be dealt with by Par-
liament, and legislation effected which
will necessitate considerable engineering
works for putting the arterial drainage
of the country on a more satisfactory
footing. The frequent recurrence of
floods, and the immense damage caused
by them, cannot be allowed to go on
without a remedy being sought.

Much valuable information as to the
best method of forming a proper organ-
ization for the management of rivers has
been elicited by Parliamentary Commit-
tees and public discussions on the sub-
ject, and individual engineering opinions
have been given as to the way in which
Floods Prevention Works should be car-
ried out. No opportunity, however, has
yet been afforded for a general expres-
sion of engineering opinion and discus-
sion of the principles on which the regu-
lation of rivers should be conducted.
Such a discussion will be highly valua-
ble, not only to those members of the In-
stitution who may hereafter be called
upon to carry out these works, but also,
as a basis for the guidance of those on
whom He the respoDsbility of deciding
the best course to pursue, and of levy-
ing the money to pay for the works.
From want of a clear perception of the
principles which ought to guide all
works for the improvement of rivers
great mistakes have been made, enor-
mous sums of money have been wasted,
and taxes levied from which little or no
benefit has been derived.

The circumstances of river basins in
this country are so various in character,
owing to geological and economical
causes, that it is not possible to lay down
any method of dealing with all rivers
alike. Still there are certain general
principles that should prevail, and which
should be borne steadily in mind in de-
signing improvements, whether of a local
Vol. XXV1L— No. 4—20.

or a general character. In the following
paper an endeavor will be made to show
what in the author's opinion these prin-
ciples are, and to illustrate them by
facts relating to one particular class of
rivers.

The rivers here dealt with are those
draining the Eastern Midland portion of
England, and are typical of the drainage
systems of flat districts, of permeable
strata discharging into sandy estuaries,
with a small rainfall, free from mountain
torrents, and rapid discharges of water
met with in the watersheds of volcanic
districts. The industry pursued on their
banks being mainly of an agricultural
character no complication arises from
the pollution by manufactories.

Large sums of money have been ex-
pended on these rivers, for which some
of the lands draining by them are heavily
taxed. Yet owing to the piecemeal way
in which this has been done, these river
basins are still subject to most disas-
trous floods. If the same amount of
money had been judiciously expended
on a comprehensive plan embracing the
whole river system, and the cost fairly
spread over the lands benefited, these
rivers would now be in a comparatively
efficient state, and competent to dis-
charge the heaviest floods without any
undue burden being imposed on the
land.

The Eastern Midlands lying between
the Trent, the Severn, and the Thames,
are drained by four rivers, the Witham,
the Welland, the Nene, and the Ouse,
which discharge into the upper end of a
large indent or bay on the east coast
known as " The Wash." There are other
small rivers draining the district lying
between the watersheds of the Ouse
and the Thames, which discharge at va-
rious points along the coast, but these
it is not intended to deal with. The
area drained by the four rivers is about
5,719 square miles; their total length
about 416 miles, and with the tributaries

282

VAN nostkastd's engijsteeking magazine.

872 miles. The number of square miles
to a mile in length of the main stream is
12.74, or 8,155 acres for the whole wat-
ershed. Including the affluents there
are about 4,015 acres to a mile of river.

These rivers drain portions of the
counties of Lincoln, Norfolk, Northamp-
ton, Cambridge, Huntingdon, Rutland,
Bedford, and Buckingham. The princi-
pal towns within the watershed are Lin-
coln, Boston, Grantham, Spalding, Wis-
bech, Peterborough, Northampton,
Lynn, Cambridge, Ely, Bedford, and
Dunstable. With the exception of
Northampton, where shoemaking is car-
ried on to a large extent, and Bedford
and Dunstable, where the strawplaiting
industry is chiefly located, these towns
are mostly agricultural centers, and are
markets for the disposal of the produce
grown on the lands around. The busi-
nesses carried on are almost entirely those
for the supply of agricultural machinery,
for the manufacture of the produce for
market, or of oil cake or other food for
the stock, and of artificial manures for
the land. The rainfall of ' the district is
small, ranging from 17.39 inches in the
driest seasons to 34.48 inches in the
wettest ; the average being 26.05 inches.

The country generally is flat, and the
elevation at the source of the rivers is
only about 300 feet above the level of
the sea. The geological formation is
Kimmeridge and Oxford clays, Oolites
with small deposits of Lower Greensand,
Chalk and Glacial drift. The lower or
fen districts are alluvium and peat.
The sources of the four rivers are not
more than about 30 miles apart, the
water producing the streams breaking
out from the Oolites near the extreme
northeastern boundary of the watershed
of the Severn. The lower part of the
watershed, comprising about 668,241
acres, is a plain, known as "The Fens,"
.now a tract of valuable agricultural land,
but formerly a morass, which in winter,
with the exception of a few elevated
spots, was little better than a lake, but
in summer afforded valuable pasturage
for the cattle of the occupiers of the ad-
joining high land. After the introduc-
tion of monastic life into this country,
settlements took place in the Fens by
some of the religious orders. The ab-
bots and priors began gradually to im-
prove portions of the fen, but no sys-

tematic attempt at reclamation was made
until the seventeenth century, when cer-
tain speculators or " adventurers " un-
dertook to drain and improve the fens in
return for a share of the lands. The
most successful of these was the Duke
of Bedford, who reclaimed a large tract
of land in Cambridge and Norfolk,
known as " The Bedford Level," much of
which is owned by the successors of the
original " adventurer."

The adventurers called to their as-
sistance Vermuyden, a Dutch engineer,
who designed his works of reclamation
on a plan similar to plans adopted in
Holland. Losing sight of the greater
range of the tides in the estuary than on
the coast of his own country, he took no
advantage of the gain to be obtained by
discharging the drainage direct into the
estuary, where low water ebbs out lower
than the North Sea, and thus securing a
natural outfall for the water. The out-
falls were neglected, embankments were
made along the main rivers, and long ar-
terial cuts through the lands to be re-
claimed, with sluices at the end to keep
out the tidal waters. Under this sys-
tem the lower part of these river-basins
became split up into a number of dis-
tricts or levels, each level dealing with
its own drainage irrespective of its
neighbors. The aggregate amount of
money thus spent in the reclamation
works was far greater than it would
have been had all contributed to the im-
provement of the common outfall.
Conflicting interests were created which
have since caused enormous sums to be
spent in litigation, and have prevented
that common action for the improvement
of the rivers which is generally admitted
to be necessary, and adding greatly to
the difficulties of the application of any
system of river conservancy.

As the original works failed to attain
the purpose for which they were in-
tended, fresh cuts were made. In many
instances the course of some rivers was
entirely diverted. Long straight cuts
were made to supersede the winding
course of some natural rivers, shorten-
ing considerably the distance the water
had to travel, and accelerating their dis-
charge. In these new rivers the flood-
banks were set in some cases as much
as a mile apart, the river channel oc-
cupying a space in the center sufficient

THE CONSERVANCY OF KIVERS.

283

possessors of
at high prices,
themselves by-

only for the ordinary discharge of water.
In floods the water overflowed the or-
dinary banks, and spread over these
': Wash lands.'' The country below be-
ing at that time almost entirely open
marsh, the outfalls were thus capable of
receiving the flood-water, aiTd the washes
being unobstructed, the floods passed
away without doing any damage to the
land, which was then all under grass.

The marsh lands below these washes
have subsequently been reclaimed, and
the outfalls otherwise choked and im-
peded, and the washes have long ceased
to answer the purpose for which they
were originally intended. Where they
have not been encroached upon by being
embanked from the rivers, they now in
times of flood become vast lakes, which
fill with water on the overflowing of
the rivers, sometimes to a depth of 6
feet, the water remaining on them for
several weeks together, presenting the
appearance of an inland sea. The pro
prietors having become
portions of these washes
have sought to recoup
endeavoring to grow crops of hay, and
in many instances by turning the fields
into arable land. During the last few
years, owing to. the continuous floods,
crops have been washed away, and the
land rendered of little value. The
miasma arising from this land, when at
length it begins to dry, after several
weeks' submergence, is prejudicial to
health. Thus what were intended by
the engineers who designed these wash
lands as flood regulators, have, by the
want of a general system of control,
become a nuisance.

The existence of these washes, the
large area they cover, and the above
facts, are sufficient answers to those
theorists who are in the habit of advo-
cating the formation of reservoirs to
regulate the streams and prevent floods.
Here, on rivers draining comparatively
a flat country, are occasional reservoirs
of 3,000 and 5,000 acres, which yet have
scarcely any effect in preventing most
severe floods on the lands above them.
Taking an average depth of water of 4
feet over the whole of the wash lands,
those on the Nene would only provide
for a rainfall of 0.297 inch over the wa-
tershed draining above them, and those
on the Welland of 0.48 inch.

THE WITHAM.

The Witham rises near Thistleton and
South Witham, a few miles north of
Stamford, at an elevation of 339 feet
above the sea. It is about 8(.) miles in
length, has five tributaries, the Brant,
the Till, the Langworth, the Bane, and
the Sleaford River, their united length
being about 98 miles. The area of the
basin drained is 1,0G3 square miles, of
which 196,G86 acres are fen lands. The
number of acres to 1 mile in length of
the river and its tributaries is 3,635.
The tidal flow only extends 8 miles, the
tide being arrested at Boston by a sluice
placed across the river, having self-act-
ing doors, which close against the tide
and open on its receding. The tide
flows from two to three hours, and at
spring tides there is a navigable depth
at the present time of about 16 feet.
Mean high water on an average of four
years (1869-72) rose 18.92 feet above
the Black Sluice sill at Boston, or 10.22
feet above ordnance datum ; spring tides,
22.02 feet ; neaps, 15.36 feet. A spring
tide which rose 23 feet 4 inches in Clay-
hole, rose 13 feet 2 inches at Boston ;
and a neap tide, which ranged 9 feet 2
inches in Clayhole, ranged 6 feet at Bos-
ton. B}r the works now being carried
on under the Witham Outfall Act of

1880, it is expected to give a naviga-
ble depth of 22 feet at the proposed
entrance to the new docks at Boston.

Between Boston and the lock at Bard-
ney, a distance of 20 miles, water is main-
tained for purposes of navigation at a
uniform depth of 9 feet. The Com-
missioners have now, under the Act of

1881, obtained power to reduce this
when necessary. In floods the regu-
lating doors at the Grand Sluice at Bos-
ton are withdrawn, and the water al-
lowed to flow without interruption.
The sluice has four openings of 16 feet
each, and the depth of water on the
sill at ordinary floods is about 10 feet,
rising as high as 14 feet in extreme
floods. The fall in the surface of the
water in floods between Bardney and
Boston is from 3 to 5 inches per mile,
and between Boston and the sea 25
inches per mile. The waterway of the
river about 2 miles below Boston is
200 feet at low water. With 10 feet
of water the area is 2,000 square feet.

284

VAN nosteand's engineeeing magazine.

The area drained through this part of
the channel is 650,392 acres, thus giv-
ing 325 acres to every square foot of
waterway. The waterway of the Grand
Sluice is 66 feet, and with a depth of
10 feet on the sill it has an area of
660 feet. The river above was orig-
inally excavated so as to give a mean
waterway corresponding with that of
the sluice. The number of acres drain-
ing through the sluice is about 448,-
835, being 680 acres to a square foot.
The area of the river at Boston at or-
dinary low water is 156 square feet,
and at high water of spring tides 2,286
square feet, a proportion of 1 to 14.6.
But in comparing this with the other
rivers, it must be borne in mind that
the section is taken only 7 miles from
the estuary, the tidal flow being ar-
rested at the Grand Sluice, 1 mile fur-
ther up the river.

The river has been considerably al-
tered below the City of Lincoln, from
which place it is mostly artificial. About
the middle of the last century the banks
on both sides of the river from Boston
to Lincoln were raised and strength-
ened, the greatest of the bends removed
by new straight cuts, and the channel
generally deepened, widened, and im-
proved. The Grand Sluice was erected
for preventing the tide flowing into the
upper reach of the river. These works
were completed in 1766, at a cost of
about £53,650. In 1811 a further
amount of £30,000 was spent in this
portion of the river. Additional works
have been carried out under an Act ob-
tained in 1865, for deepening and re-
moving obstructions from the channel,
and strengthening and raising the banks.
The cost was about £50,000. The nav-
igation authorities have expended, dur-
ing the last fifty years, about £60,000
in straightening and training the tidal
portion of the river below Boston.
Under an Act obtained in 1880, works
are now being carried out for making a
new outfall by a cut 2J miles in length,
by which the distance will be shortened
l| mile, and the shifting sands at the
mouth of the river avoided. It is ex-
pected that this will give relief of at least
3 feet in the low-water mark at the
drainage sluices.

The cost of the works executed up to
the present time is upwards of £300,000,

and the works for the outfall are esti-
mated to cost £120,000 more. Beyond
this a large sum has been spent on
works for improving the river by the
owners of the upper navigation. The
cost has been met by taxes on the low
lands and by dues on the shipping. The
taxes on the fen lands for river works
vary from Is. to 5s. 6d. an acre, in ad-
dition to what has to be paid for works
of interior improvement, which on some
of the fens brings the amount of drain-
age taxation up to 16s. per acre. This
amount extends over a length of 35
miles of the lower part of the river, or
only about one-half of its course. Fur-
ther expense has been incurred in
straightening and improving the upper
reaches, by which the water is discharged
more rapidly into the lower part, but the
landowners contribute nothing to the
works below Lincoln. Notwithstanding
the improvements, the river is incapable
of discharging the water as quickly as it
is poured into it, owing to the defective
outfall at the sea, to the obstruction
caused by the sluice at Boston, the weirs
at Lincoln, and the inadequacy of the
channel between those places, and con-
sequently the floods on this river have
been increasingly frequent and disas-
trous. The lower part of the city of
Lincoln has been several times under
water, the houses for a time being ren-
dered uninhabitable and the large engi-
neering works stopped. In the winter
of 1876, when several of the interior
banks were broken, 40,000 acres of land
were under water, people were driven
from their houses, and cropping was lost
to the estimated value of £100,000. In
1878 and 1879 there were very heavy
floods; and in the autumn of 1880 a
large tract of land was again submerged ;
the corn stacks were standing several
feet in water, and sheaves of corn which
had not been carried away were floating
about in the fields. Not only were the
farmers injured, but much valuable food
was destroyed.

THE WELLAND.

The Welland rises in a gentle range of
hills between Lutterworth and Market
Harborough, near the source of the Ise,
a tributary of the Nene. It is about 72
miles long, has three tributaries, together
65 miles long, and drains about 707

THE CONSERVANCY OF RIVERS.

285

square miles, of which 76,854 acres are
fen land. The number of acres to 1 mile
in length of the river and its principal
tributaries is 3,302.

The "Well and has a tidal course of 20
miles ; extreme tides reach as far as
Crowland. A spring tide which rose 23
feet 4 inches at Clayhole rose 12 feet 2
inches at Fosdyke bridge, 8 miles from
the estuary, and 4 feet at Spalding, 15
miles from the estuary. When the river
is thoroughly scoured out to its full
depth the rise at spring tides is 8 feet,
giving 10 feet at high water of spring
tides. The range of a neap tide, which
was 9 feet 2 inches at Clayhole, was 5
feet 5 inches at Fosdyke, but the tide
did not reach Spalding.

The mean inclination of the surface of
the water between Spalding and Clay-
hole at ordinary low water is 14 inches
per mile. During floods, in the trained
portion of the channel below Fosdyke
bridge, the inclination is 9 inches per
mile, and between Fosdyke and Spalding
2 feet per mile. In large floods the
average inclination from Spalding to low
water of spring tides in the estuary, 15
miles, is 21 inches per mile. Owing to
the want of prolongation of the trained
channel, the fall from Fosdyke bridge to
low water in Clayhole, 8 miles, averages
about 18 inches per mile, due to the
great fall between the end of the trained
work and Clayhole..

The average waterway of the river at
Spalding is about 40 feet, and the area
in floods 400 square feet. The drainage
area discharging there 300,000 acres,
giving 750 acres to a square foot. The
mean width of the trained channel below
Fosdyke is 120 feet ; the area of the
waterway with 10 feet depth of water is
1,200 square feet. The drainage area
discharging through this channel is about
452,480 acres, or 377 acres to a square
foot.

The area at Spalding at low water is
about 73 square feet, and at high water
spring tides 485 square feet, a propor-
tion of 6.65 to 1.

The Welland retains its ancient course
more nearly than any of the other rivers,
yet it has been considerably altered.
The river was made navigable from
Stamford to the sea by improvements in
the channel of the river, straightening
the same by new cuts, and by the erec-

tion of locks, &c, the first lock on the
river being about 13 miles above Spald-
ing. Subsequently the adventurers of
Deeping fen, in order to obtain a better
outfall for their drainage, widened and
deepened the river below Spalding. In
the year 1801 a new cut was made from
the reservoir 8 miles below Spalding,
and the open marshes above Fosdyke
were enclosed. About forty-five years
ago the work of training the river by
fascine work through the shifting sands
below Fosdyke bridge was commenced
and continued for a length of 3 miles 30
chains. This training had the effect of
lowering the low-water level at Fosdyke
bridge 7 feet. The whole of these works,
so far as they relate to the improvement
of the river as the outfall of the drainage
of the country, were paid for by the Fen
land in the low level of the river basin,
assisted by dues levied on the shipping
using the artificial channels.

The arterial drainage of this district is
still in a very defective condition, the
channel not being sufficiently adapted to
carry off the rainfall as rapidly as it is
collected in the river. The banks which
protect the fens are constantly being
broken, owing to the channel being over-
full and the fens flooded. The repeated
floods of the last few years have done an
immense amount of damage by submerg-
ing the land and destroying the crops.
In July 1880, in addition to thousands of
acres of land which were submerged, the
whole of the lower part of the town of
Stamford was flooded, as were also the
villages of Market Deeping, Elton,
Maxey, and others on the course of the
river, the water rising to a height of 3
and 4 feet in some of the houses. Again,
in the autumn of the same year, a flood,
almost as extensive and if anything more
disastrous in its results, occurred. Al-
though floods so calamitous are excep-
tional, yet their frequency and the large
area of land thrown out of cultivation,
are sufficient to demand that such alter-
ations should be made in the river, as
the main outfall of the drainage of the
district, as to render it efficient for its
purpose.

THE NENE.

The Nene rises in two springs at Dav-
entry, and owing to its windings, al-
though in a direct course the distance is

286

van nosteand's engineering magazine.

only 60 miles, the length of the river is
99 miles. It has three tributaries : the
Ise, the Harper, and Willow Brook, their
united length being 52 miles.

The Nene has a drainage area of about
1,055 square miles. The number of acres
to 1 mile in length of the river and its
tributaries is 4,474.

The tidal flow is 34 miles, at spring
tides, reaching Northey Gravel within
2f miles of Peterborough, and at extreme
tides even as far as Peterborough. The
tide flows three and a half hours at Sut-
ton bridge, 7 miles from the estuary, and
two and three quarter hours at Wisbech,
15 miles from the estuary. A spring
tide, which rose 23 feet 3 inches in the
estuary, rose 20 feet 6 inches at Sutton
bridge, and 15 feet 2 inches at Wisbech.
A neap tide of which the range was 9
feet 1 inch in the estuary, ranged 8 feet
5 inches at Wisbech. The navigable
depth of water at Wisbech is about 22
feet at high water spring tides, and 3
feet at low water. From observations
made by Sir John Coode, M. Inst. C.E.,
it appears that, owing to the tide being
throttled by the contracted form of the
lower part of the channel, it has not free
ingress and egress, and does not reach
the limit of its flow until some time after
the ebb has commenced at the lower end.
Thus the particular tide observed ebbed
three and a quarter hours at the lower
end of the trained portion of the channel
before it had reached the " Dog in the
Doublet," 25 miles above, and then con-
tinued flowing there for forty-five
minutes. The water rose 6 feet at the
upper end, while it fell 6 feet 11 inches at
the lower end. Thus there are two strong
currents in the river running simul-
taneously in opposite directions, the ebb
towards the sea and the flow towards
Peterborough. High water spring tides
is 7 feet lower at Peterborough than at
the outfall at Stone Ends, and at neap
tides it is 8 inches lower at Cross Guns,
24 miles from the outfall.

The mean inclination of the surface of
the water at low water from Peter-
borough to the sea is at the rate of 5.63
inches per mile. This rate varies con-
siderably along the different sections, the
minimum being 2 inches per mile along
the lower reach, and the maximum at the
Horse Shoe bend at Wisbech 14f inches
per mile. In severe floods the inclina-

tion from the South Holland sluice above
Sutton bridge to low water at spring
tides in the estuary, 8J miles, is at the
rate of 10J- inches per mile. Through
Wisbech, in great floods, there is a fall of
3 feet in less than a mile.

The mean waterway of the river in the
upper reach, a short distance above
Wisbech, is 50 feet, giving an area with
10 feet depth, of water of 500 square
feet. The area of land draining through
this part of the river is about 564, 70Q
acres, or 1,129^ acres to a square foot.
In the lower reach, between the stone
banks of the trained channel, the water-
way is about 220 feet, and with a depth
of 10 feet the river has an area of 2,200
square feet. The area of land drained is
about 675,200 acres, being 307 acres to a.
foot. Taking the area above Wisbech at
ordinary low water at 240 square feet,
and at high water of spring tides 1,595
square feet, the proportion of tidal to
fresh water for the ordinary flow is 6.65
to 1.

The Nene is navigable from North-
ampton; it enters the fens at Peter-
borough, and then divides into two
branches, one branch, the old river, joins
the Ouse by a branch from Stanground
sluice. The main stream runs by Smith's
Learn through the wash lands and Wis-
bech to the sea. The Nene has been
more altered by various works than any
other river. From Peterborough to the
sea it is nearly a new river. Bishop
Morton in 1478-86 first commenced the
alterations, diverting the river from its
original course by a new cut from Peter-
borough to Wisbech, about 11 miles in
length, which shortened the course of
the water 7 miles. In 1726 the present
channel of the river between Peter-
borough and Guyhirne was made, its
course being parallel with Merton's
Learn. The banks are about -J- mile apart,
leaving 3,500 acres of low-lying meadow
land or "washes " At Guyhirne, 6 miles
above Wisbech, these banks come to-
gether and are close upon the river.
From the Horse Shoe bend towards the
sea below Wisbech a channel was cut by
King Charles. In 1773 a new cut was
made 1^- mile in length 5 miles from
Wisbech, since known as " Kinderley
cut ; " and between 1827 and 1832 this
was continued by the Woodhouse, or
" Pauper's cut," so called from a number

THE CONSERVANCY OF BITERS.

2S7

of paupers haying been employed on the
works. About fifty years ago the im-
provement of the river below these cuts
was continued by excavating and scour-
ing a new channel through the Cross
Key washes from Gunthorpe sluice to
Crab's Hole, a distance of 5 miles, with
further training banks through the sands
about 1J mile in length. A large tract
of land was at the same time reclaimed.
The new outfall lowered the low water
at the North-Level sluice 10 feet. In
1813, before the last improvement was
made, the fall in the surface of the river
was at the rate of 3 feet per mile.
Afterwards it was only 3 inches in the
mile. In 1852 further powers, were ob-
tained for improving the river between
Peterborough and the sea, and after
an expenditure of £200,000 the works
were discontinued without any material
improvement having been effected. The
alteration in the channel of the river
greatly augmented the range of the
tides. In 1769, according to a report of
Golborne, spring tides only rose 4 feet
at Wisbech, and neap tides did not reach
the town ; after the new channel was
made they rose from 15 to 16 feet.

Within the last century the amount
spent on the improvement of the main
channel of the Nene has been upwards of
£450,000, about one-fourth of which sum
was raised on the navigation dues, to
meet which all ships entering the port
are subject to a charge of Is. 0£d. per
ton -register, and the remainder by the
fen land. The taxes on the land to meet
this outlay reach in some cases 15s. an
acre, and yet the land is occasionally
flooded. The river is in a most unsatis-
factory condition, thousands of acres of
land along the valley being sometimes
inundated, and even the streets of Peter-
borough flooded and people driven from
their houses, while the whole arterial
drainage system suffers from its defect-
ive condition.

THE OUSE.

The Ouse rises at an elevation of 300
feet above the sea in numerous springs ;
these escape from the Oolite escarpment
at its junction with the Lias Clay above
the valley of the Cherwell, between the
Ouse and the Thames, and within 4 miles
of one of the sources of the Nene. The
head of the main branch is about 87

miles from the sea, but owing to the
tortuous course of the river the length
of the channel is 156 miles. It lias ten
tributaries, their united length being 241
miles. The drainage area is 2,894
square miles. The number of acres to 1
mile in length of river and tributaries is
4,672. The river for the last 50 miles
of its course runs through a flat low-
lying district, and has been embanked
from St. Ives downwards. Spring tides
flow a considerable distance up the
Hundred-Foot river, or nearly to Earith,
20 miles beyond Denver sluice, giving a
tidal course of 40 miles.

The average rise of a spring tide at
the Free bridge above Lynu, as taken
from the records observed there over a
period of seven years (1869-75) was
18.51 feet above zero, which is about
1.31 foot above low water of spring tides.
The highest tide observed during that
period was 22 feet 6 inches, an average
neap tide was 12.04 feet, and the mean
of all tides 15.54 feet, or 10.59 feet above
ordnance datum. A spring tide, which
rose 23 feet 3 inches above low water in
Lynn Roads, rose 22 feet 6 inches at
Lynn ; and a neap tide, which ranged 9
feet 1 inch in the estuary, ranged 9 feet
5 inches at Lynn. The tide flows for
about 5 hours at Lynn.

The ordinary low-water inclination of
the surface of the water along the Eau
Brink cut is about 3 inches per mile. In
large floods the mean inclination from
Denver sluice to low water in the estu-
ary, a distance of 19 miles, is at the rate
of 9 inches per mile. From Denver to
Lynn the surface inclination is 12 inches,
and from Lynn to the estuary 8
inches.

The area of the waterway of the river
above Earith is very irregular. That of
the channel near Earith is only 243
square feet, while 7 miles further up the
river, near St. Ives, has a sectional area
of 672 square feet. At Over Court
Ferry the area is 492 square feet. The
area of the outlets for flood-water above
Earith was found by Mr. Abernethy,
President Inst. C.E., in 1875 to be 4,233
square feet, while below the Seven-hole
sluice at Earith it was only 2,058 square
feet. The shuttles at the Seven-hole
sluice are not lifted till the flood-waters
have risen 4 feet 6 inches above the level
of the wash lands, or until a large part of

288

VAN NOSTKAND'S ENGINEERING MAGAZINE.

the country is flooded. The fall in floods
from the upper to the lower side of this
sluice is 2 feet, caused by its restricted
size as an outlet for the large area which
has to drain through the sluice. In the
Eau Brink cut the area in floods is
about 2,620 square feet ; and the drain-
age area being 1,852,160 acres, gives
about 707 acres to a foot. In the Marsh
cut the dimensions of the cut, originally
set out with slopes 4 to 1, have increased
by the washing away of the banks from
265 feet at the bottom to an average of
425 feet, and from 500 feet at the top to
an average of 594 feet. The depth
originally was 10 feet 4 inches, and now
varies from 10 feet to 19 feet, averaging
12 feet 8 inches. The channel below
the Marsh cut, where it is confined by
guide-walls of stones and fascines, is 400
feet wide, and, taking the depth at 19
feet, gives 463 acres to a foot of sectional
area of waterway.

The section of the Eau Brink cut has
also become very irregular since its first
formation. From a number of measure-
ments in 1862 it was found that the
sectional area at low .water in some
places was double that in others, and
the depth at low water varied from 17
feet 3 inches to 2 feet 9 inches. The
mean of forty-three measurements gave
the area at ordinary low water as 1,824
square feet, and at high water of spring
tides 9,421 square feet, a proportion of
5.16 to 1.

The average low-water level of ten
years, 1844-53, previous to the comple-
tion of the Marsh Cut, was 2 feet 5J
inches above the datum at the Free
bridge, and for ten years after the open-
ing of the cut, 1866-75, 9 J- inches be-
low, showing an average gain of 3 feet
2 1 inches. The extreme low water varies
from 3 feet 6 inches above datum to 3
feet 6 inches below, or a range of 7 feet.
The average low-water level of spring
tides at the Free bridge is now about 1
foot 3f inches below datum, or 3 feet 8
inches above low-water spring tides in
the estuary ; and during neap tides 2f
inches above datum, or 5 feet 3 inches
above low water.

The Ouse stands first of all the Fen
rivers in the large amount of money
which has been expended in its improve-
ment. Without taking account of what
was done by the early adventurers, up-

wards of £800,000 have been raised and
expended in making new cuts, and other-
wise improving that portion of the river
which passes through the Fen land. The
benefit of these improvements has been
enormous, the low-water level having
been depressed 12 feet.

Vermuyden began the alterations in
this river in 1638 by making a new cut
21 miles long and 70 feet wide, called the
Old Bedford river, from Earith, where
the river enters the fen jurisdiction, to
Denver sluice. In 1652 the New Bed-
ford, or Hundred-foot river, was made
parallel with the other ; and banks were
raised on the north side of the old Bed-
ford river and the south side of the new
river, leaving an area of 5,000 acres of
wash lands between. By this cut the
course of the river was shortened 10
miles ; and the old course of the river
being maintained, there were three chan-
nels for the river. In 1748 Denver sluice
was erected, by which the tidal flow was
stopped from going up the old river
course, but was still allowed a free run
up the Hundred-Foot river. Subse-
quently the Hermitage, or Seven- hole
luice, was erected at Earith, and all thes
water coming from the basin of the
Ouse above this, extending to 756,000
acres was discharged by the new river,
while the old Bedford river and the wash
lands afforded receptacles for the waters
in extreme floods. By an Act passed in
1812 the owners were allowed partly to
embank the washes, and they have since
been gradually encroached upon, their
use as flood-regulators being otherwise
destroyed.

The Eau Brink cut was originally pro-
jected by Kinderley in 1720, and the Act
was obtained in 1795; but it was not
completed until 1821. The original esti-
mate was £39,985 ; the ultimate cost,
£600,000. The length of the cut is 2£
miles,- the old course of the river being
5 miles. The effect of the cut was to
lower the low water 6 feet at Denver
sluice, and 8 to 9 feet at Eau Brink,
where the new cut joined the old riyer.
In 1853 the Norfolk Estuary Company
made a new cut through the marshes be-
low Lynn 2 miles in length, and con-
tinued the channel by training through
the Vinegar middle sands for a distance
of about a mile. The cost of this work
was upwards of £200,000, towards which

THE CONSERVANCY OF BITERS.

289

the drainage and the navigation con-
tributed £110,000. This cut shortened
the course of the river, and depressed
the low-water level 3 feet at Lynn. Since
the opening of the Marsh cut the river
has been further improved by dredging
away a large clay bar or shoal lying be-
tween the Eau Brink cut and the Marsh
cut.

INLAND NAVIGATION.

The present condition of the inland
navigation seriously affects these rivers,
and is one chief cause of their incapacity
for carrying away flood-waters. Owing
to the position of the Wash with refer-
ence to the Netherlands and the Conti-
nent, Lynn and Boston were once prom-
inent ports, ranking only second to
London and Bristol ; and although a
great portion of this trade was diverted
by the opening up of Hull and other
ports on the east coast, yet up to the
time of the construction of railways there
was a large export trade of wheat and
agricultural products, and an import of
coals and other goods which were dis-
tributed throughout the midland part of
England by these rivers. Water carriage
was almost the only means of conveying
heavy products into the country, and of
exporting the corn and wool ; as this
traffic increased, the rivers, where they
became shallow, were canalized and made
navigable by locks or staunches. Thus
Bedford by the Ouse, Northampton by
the Nene, Stamford by the Welland, and
Lincoln by the Witham, with other
smaller towns, were placed in communi-
cation with the sea.

So long as these navigations were
maintained in order, the shoals cleaned
out as they accumulated, the locks and
staunches preserved in efficient condition,
and the weeds cut or kept down by the
traffic of the boats, the rivers even in
their artificial state of canalization were
capable of discharging the flood-waters ;
but since railways have diverted the traffic
from these inland rivers, navigation has
ceased, the works have gone to ruin for
want of funds to maintain them, and
shoals and weeds choke the channels.
The rivers have become in a far worse
condition to discharge the drainage of
the country than when left in their
natural state, and constant floods are the
consequence. The proprietors of the

navigations, who have suffered greatly
by the loss of the dues, although unable
to fulfil the duties belonging to a proper
maintenance of the streams, still cling to
the remnant of traffic left. For this they
adhere to their rights as to the holding-
up of the water, without having the
means to adapt the rivers to the modern
requirement of drainage by enlarging the
capacity of the weirs, so as in times of
flood to discharge waters sent down at a
much greater rate than formerly.

On the Witham, for a distance of 30
miles between Boston and Lincoln, the
river is practically a canal. The tide is
stopped by a sluice at Boston, and a weir
and locks had to be constructed at Bard-
ney and Lincoln. The inland water is
held up to a constant height on the sill
of this sluice by penstocks, for the pur-
poses of the navigation. The navigation
having been taken over by the Great
Northern Railway Company, the works
are maintained in efficient condition, but
the obligation imposed by the original
Act of holding up the water seriously
affects the drainage. The 'river Slea,
from Sleaford to the Witham, was made
into a canal in 1792. The navigation on
this river having almost entirely ceased,
the company was dissolved by an Act
recently obtained. The Bane, another
affluent of the Witham, was also canalized
forming a navigation from the Witham
to the town of Horncastle ; but the dues
obtained are insufficient to maintain the
works in proper order.

On the Nene, which is canalized from
Peterborough to Northampton, the navi-
gation is reduced to a few barges. The
constant floods on this river are ascribed
in a great measure to the defective con-
dition of the works. The proprietors of
the navigation, on whom was cast the
duty of maintaining the river, no longer
have the funds, and there is nobody to
take their place. The same thing has
occurred on the Ouse between Earith
and Bedford.

On some of the affluents of these rivers,
which under legislative powers granted
last century had been converted into
"navigations," the proprietors have ob-
tained Acts of Parliament relieving them
of their rights and liabilities, and there
is now no jurisdiction over these rivers,
or anybody responsible for removing
shoals or cutting weeds. The beds of

290

VAN NOSTRAND'S ENGINEERING MAGAZINE.

these streams have consequently grown
shallow, and the rivers are no longer
capable of acting as efficient arterial
drains. Thus on the Ivel, an affluent of
the Ouse, the navigation trust created
in the reign of George II., was abolished
in 1876. The river is said to have since
diminished one-half in width and one-
half in depth, and the bottom is being
gradually raised above the level of the
land. In like mariner the Lark, another
canalized affluent, has almost entirely
silted up since the navigation of the
river ceased. The Ouse itself above
Earith is obstructed by numerous shoals,
and an enormous growth of weeds.
These were originally kept down by the
constant passage of the vessels, and the
shoals were removed by the trustees of
the navigation.

It is no doubt a great advantage to
the water supply, and also for the water
power of the country through which
these rivers pass, and conducive to the
economical conveyance of gravel, stone,
lime, manures, and other heavy materials,
where time is of no great consequence,
that the locks, weirs, an£ works should
not be abandoned, and the rivers restored
to their natural state ; but it is desirable
that these works should be placed under
a jurisdiction interested in and having
control over the drainage, and that by
the enlargement and improvement of the
weirs and other works the rivers should
be placed in a state of efficiency.

CAUSE OF FLOODS.

From the improved system of drain-
age now pursued, necessitated by the
higher cultivation of the land, the rain
is more rapidly discharged into the rivers.
The water is no longer suffered to fill the
land like a sponge, and pass off either
by evaporation or slow percolation
through the subsoil, but rapidly soaks
through the soil broken up and disinte-
grated by steam ploughing and deep
cultivation, and as soon as the sub-
stratum is saturated to the level of the
drain -pipes, the rain-water is carried to
the ditches. Efficient pipe drainage ne-
cessitates clean ditches, and the straight-
ening and improving of all arterial drains
and minor watercourses. Thus every
impediment is removed from the free
flow of the water to the river. Large

tracts of water known as meres, which
formerly acted as reservoirs, have been
drained; woods and plantations which
absorbed and held the rainfall have been
stubbed up. Villages and towns are
drained, and everywhere, whether in
town or country, every effort is made to
prevent stagnation, and speedily to void
the water. An increase in the rainfall
has also no doubt contributed to the in-
crease of floods. On examining the sta-
tistics of rainfall kept at Boston for the
past fifty years, it appears that there has
been a considerable increase in the an-
nual rainfall during the last few years,
and especially during the last five. The
average annual rainfall of the last five
years has been 29.04 inches, or a greater
quantity than previously recorded dur-
ing a like period, and 5.62 inches above
the average of the last fifty years. The
next wettest period was 1846-50, when
the average annual fall was 4.22 inches
less than during the last five years.
Taking ten-year periods, the average
annual rainfall of the last ten years has
been 4.34 inches greater than of the
previous ten years, and 4.78 inches
more than the ten years 1851-60, and
1.83 inch over 1841-50. Taking twenty-
year periods, the last twenty years is
1.14 inch in excess of the previous
twenty years and 4.11 inches in excess
of the previous fourteen years. The
largest increase has been in the months
of September, February, and December,
and the least in July and October.
During the last few years September has
had the greatest fall, and March the
least.

Meantime no provision has been made
to meet this more rapid discharge. In
the upper reaches of the rivers no ade-
quate jurisdiction exists to prevent ob-
structions, to compel the maintenance of
works, or to levy taxes for carrying out
improvements. In the lower reaches the
works have been done in sections, and
without reference to the general drainage-
system of the rivers, and have been for
the benefit of, and are paid by, the low
lands, the owners of which of course are
opposed to any improvements which will
bring the upland waters on to them more
rapidly. In fact, so jealous are the
managers of the lower reaches of the
river, that powers have been obtained

THE CONSERVANCY OF RIVERS.

291

enabling them to regulate the quantity
arriving from the upper reaches. On the
Oose at Earith a sluice regulates the
flow of water from above, in which the
openings are not only too contracted to
allow the flood-waters to pass freely
through, but the shuttles are not lifted
until the water has risen to more than
flood-height on the lands above. In the
Witham, at Lincoln, the quantity of the
discharge is regulated by a weir, which
is inadequate in times of flood, but any
increase in the size of which is prevented
by the Commissioners having the control
of the drainage below, the consequence
being that the lower part of the city and
upwards of 15,000 acres of land above
this weir are frequently flooded.

The openings of the bridges across the
rivers, most of which were built before
the conditions of drainage were altered,
are many of them totally inadequate to
the discharge of the waters, and great
discrepancies exist in the area of the
waterways. Thus Mr. Abernethy states
in his report on the Ouse that the bridges
over the Hundred-Foot river have only
half the area of the waterway of those at
St. Ives 12 or 13 miles higher up.

The growTth of weeds, and the increase
in the cesses or banks of the rivers which
have gradually encroached on the water-
way, form another serious and increasing
obstruction. Owing to the careless way
in which the wreeds are cut in some of
the rivers, they are allowed to float
down the stream, settling in the shallow
places where sand and alluvium collect,
in time forming large shoals, and even
islands, in the center of the streams.

Where watermills exist there is no
jurisdiction to compel the miller to main-
tain his wrorks and regulate the weirs so
as to give sufficient waterway in times of
flood. Water-power is too valuable to j
be done away with, and the holding up J
of the water is a great advantage to the
locality; but the owner should be placed
under such restrictions that his weir
and by-passers should not be of suf-
ficient capacity, and he should not be
allowed to interfere with the efficient dis-
charge of the water during floods.

In like manner the weirs belonging to
the navigation need remodelling, and the
works to be placed under an efficient
system of supervision along the whole
river.

The effect of the floods of recent years
has been most disastrous to the owners
and occupiers of land from the losses
they have incurred, and to the nation
generally from the immense amount of
produce destroyed. Thousands of acres
of corn have been ruined by the summer
floods, and land has been put out of cul-
tivation by floods in the winter. The
hay crops have been floated off the mead-
ows and carried down the rivers,, and a
large area of rich pasture land has been
so long inundated that the herbage has
been rendered valueless. Additional
taxes have also to be levied to pay for
breaches in the river and drain banks
caused by the floods, and for the main-
tenance of steam-power to pump the
water off the flooded lands. It is not
easy to calculate the loss which has been
incurred during the last few years, but
it certainly very far exceeds any sum re-
quired to place these rivers in a satis-
factory condition.

REMEDY.

The works necessary for the preven-
tion of floods in these rivers require to
be carried out on a comprehensive scheme,
commencing with the outfall and work-
ing upwards throughout the whole length,
of the channel.

The four rivers here specially referred
to, discharging into the head of a bay or
estuary abounding in shifting sands, are
liable to have their mouths choked. The
conflict between the ebb current and the
flood invariably has a tendency to throw
up a bar at the point wdiere the confined
channel debouches into the open. All
works of improvement in the way of
training and confining the channels
ought therefore to be progressive and
continuous, gradually pushing the con-
fined channel forward to deep water.

In carrying out these training works
the walls require to be at such a height
and width as to prevent any retardation
or choking of the tidal flow. The object
to be sought is to give a free action to
the tidal current as the principal agent
in maintaining these channels in their
most efficient condition, and to ensure
that the last of the ebb shall be directed
along a definite channel, so as to take
every advantage of its scouring power.
For this purpose the width of the chan-
nel should decrease from the sea grad-

292

VAN NOSTRAND'S ENGINEERING MAGAZINE.

ually, and the training walls, commenc-
ing at the lower end with a height equal
to low water of neap tides, should, as
they advance, reach to that of half-tide
level.

Already the outfalls of the Nene and
of the Ouse, which had been trained to
deep water, are encumbered with sand.
In the Nene the depth of water at the
■end of the trained channel has gradually
decreased from 9 feet to 2 feet, the depth
in the trained portion being 8 feet.
Across the outfall of the Ouse there is a
sand-bar, with only a depth of water 5
feet against 9 feet in the trained chan-
nel. In both cases the training requires
to be carried seaward slowly, but con-
tinuously, or the advantages gained will
disappear. The Welland discharges into
& sand bed four miles distant from deep
water ; in fact, it may be said that when
the water leaves the fascine work it no
longer has any denned channel, but
meanders over the sands, continually
shifting its course. The Witham is in
the same condition, but works are now
being executed to carry the channel to
deep water.

Notwithstanding the bars forming at
the mouths of the Nene and the Ouse,
the advantage of the improvements al-
ready effected in the outfalls of those
channels is shown by a comparison of
the level of low water in floods with that
of the Witham. Taking each river at a
point 8 miles from the estuary, the aver-
age level of low water of the same flood
over a period of seven days was 16 feet
6 inches above low water of spring tides
in the estuary in the Witham ; in the
Nene 7 feet 7 inches above, and in the
Ouse 5 feet 6 inches above ; showing a
difference of 11 feet in the low- water
level between the Ouse and the Witham.

The author has not been able to col-
lect sufficient data to form any definite
opinion as to the result of the works car-
ried out in these rivers in raising or low-
ering the level of high water; but by a
comparison of four years' tides at Lynn
and Boston, it appears that mean high
water is about 4 inches higher at Lynn
than at Boston, which would show that
the proper regulation of the channel has
not a tendency to lower the high-water
mark.

The value of tidal waters in maintain-
ing the channels of these rivers in an

efficient condition is of the utmost im-
portance ; and the deductions drawn
from observations lead the author to an
opposite conclusion to that laid down in
the paper by Mr. W. R. Browne, M. Inst.
C.E., on the relative value of tidal and
upland waters in maintaining rivers, es-
tuaries, and harbors. It is not contended
that the enclosure of the marshes re-
claimed by the training works has had
any material influence on the outfall, the
silting up of which is, as already ex-
plained, due to other causes, and would
equally have taken place had these
marshes remained open ; but for the
maintenance of the channel a free flow
and ebb of the tidal water up and down
the river is essential to prevent the sand
carried up with the tide from being de-
posited. So long as the water is in mo-
tion only a small portion of the sand
which is held in suspension settles ; but
where there is an obstruction to the
tidal flow, and the water remains quiet,
the heavy particles at once begin to sink
and accumulate. In summer, when the
flow of fresh water is small, this deposit
remains. The quantity of water at
spring tides in the embanked channels of
these rivers is ordinarily six times as
great as the upland water, and, being al-
ways in motion, must therefore have a
greater effect in maintaining the chan-
nels of the rivers. The Ouse is in the
best condition to allow a free run of
tidal water ; the Witham the worst. In
the former river the tidal flow is 40 miles,
and, even in the driest season, scarcely
any silting up of the reaches of the chan-
nel occurs. In the latter the tidal flow
is only 7 miles, the tide being stopped
by a sluice; the deposits have been so
great in dry seasons as to raise the bed
of the river upwards of 11 feet at the up-
per end, and an average of 8 feet over
the whole length of the trained portion
of the channel, leaving upwards of 1,500,-
000 tons of silt and sand to be washed
out by the winter floods, which have had
to rise nearly high enough to submerge
the country before they could flow over
the deposit. In the Welland, which has
a smaller drainage area, but a tidal flow
of 20 miles, during the same season the
depth of the deposit left at the head of
the tides did not amount to more than
2 feet 6 inches.

Following the improvement of the out-

THE CONSERVANCY OF RIVERS.

293

fall, the channel requires regulating
throughout its whole length by widening
and deepening in parts and confining the
low-water level where too wide so as to
give a general uniformity throughout.
Too great a width impedes the free dis-
charge almost as much as where the
channel is too restricted. By the diminu-
tion in the velocity of the current owing
to the greater capacity, deposits take !
place and shoals are formed through
which the water continually alters its !
course as the ebb or the flood current
is the stronger. In the marsh cut of |
the Ouse the banks have been gradually
washed away, and the channel has be-
come considerably wider than in the
trained portion below; consequently
shoals are forming, and the section of
the channel has become very irregular,
causing disturbance and increased fric-
tion and restricting the area of dis
charge.

Where the water is held up in the
upper reaches, the weirs should be
adapted to the largest flood discharge,
as should all bridges and other struc-
tures across the waterway. While suffi-
cient waterway should be secured for all
floods, the low water channel should be
so restricted as to maintain its scouring
power in the fullest efficiency. It is in
the adaptation of the channel to the
normal flow, and also to the flood dis-
charge, that the greatest difficulty oc-
curs. The proportion between the one
and the other, even in the flat district
of the river basins here dealt with, may
be taken as 10 to 1. Extreme floods oc-
cur only at uncertain and distant intervals.
During the last thirty years there have
been only twelve floods in this district
which have done any serious amount of
damage. Therefore if the channels be
made sufficiently capacious to carry off
these, they would be far too large for the
ordinary discharge, and would become
choked with shoals and weeds. The
great expense and waste of land which
would result from a channel made suffi-
ciently capacious to carry off excessive
floods, at once show that any such idea
is impracticable.

In river improvement it must always
be a matter of consideration whether the
advantage to be gained by any particu-
lar scheme will be equal to the outlay,
and whether it be not better to allow

tracts of low-lying land, which are now
occasionally flooded, to remain so, than
to spend more than the value of their fee
simple in protecting them. As pasture
land they would always have a certain
value, and where the owners have broken
up such tracts into arable land, they
have done so knowing the risk, and
should abide by it.

A careful investigation into the rain-
fall in the Witham basin of the last four-
teen years tends to the conclusion that
the height of the floods is not entirely
due to the actual amount of rain falling,,
as much depends on the condition of the
land and other circumstances prevailing
at the time. Taking the rainfall of Bos-
ton as typical of that of the Witham and
Welland basins, a fall of 2£ inches in
three days in July, 1867, only raised the
water in the main drains 3 inches,
whereas the same quantity, in July, 1872,.
made very heavy freshets in the river,
and in July, 1880, caused a serious flood.
Again, in 1868 although the rainfall for
the autumn was heavy and continuous,
and 6 inches above the average, yet the
water in the Witham had not risen to
flood height until the end of December.
On the other hand, a fall of 1.66 inch of
rain and snow in January, 1867, rapidly
filled the rivers and flooded a consid-
erable area of fen lands, although the
rainfall for the previous period had not.
been excessive.

It has generally been the custom in
designing fen drainage to allow at the
rate of a continuous fall of 0.25 inch of
rain during , twenty-four hours. This
calculation was adopted by Sir John
Hawkshaw, Past-President Inst. C.E.,
in his report for the discharge of the
whole basin of the Witham, and also for
the large pumping engines at Lade Bank,
for draining the East Fen. Sir John
Coode, in his scheme for the improvement
of the North level drainage in the Nene,
provided for 0.25 inch, although he
considered 0.187 inch would be all that
would come daily to the outfall. Dur-
ing floods he ascertained that a quan-
tity equal to 0.10 inch over the whole
area of 79,855 acres was daily dis-
charged.

During the last few years, the rainfall
in the Witham district, if taken over
seven days, would give a daily mean of
0.37 inch, or if over fourteen days, 0.2£

294

VAN NOSTKANDS ENGINEERING MAGAZINE.

inch, the maximum for the seven-day
period being 0.63 inch, and for the four-
teen days, 0.34 inch. Although at such
times the ground is fully saturated, and
in an exceptional condition, it is not
possible that the whole of the rain which
falls could be delivered at the outfall.
The mean discharging capacity of the
four rivers is equal to 0.094 inch every
twenty-four hours, allowing a velocity
of 3 feet per second (about 2 miles an
hour).

To adapt the channel to the discharge
of 0.25 inch in twenty-four hours would
therefore require that they should be
made nearly three times their present
size, a course which, even if practicable,
would render them far too large for all
ordinary discharges. Provision for a
continuous discharge of 0.25 inch of rain
every twenty- four hours would require,
with a velocity in the channel of 3 feet
per second, a sectional area equal to 1
square foot for every 285 acres, whereas
at the present time there is only an
average of 1 square foot to every 816.6
acres.

The present discharging capacity of
the Witham is equal to 0.105 inch of
rain in twenty-four hours ; of the Wel-
land, 0.096 inch; of the Nene, 0.063
inch; and of the Ouse, 0.101 inch; and
this is not sufficient to prevent flooding.

It becomes, then, necessary first to
provide a channel for the ordinary dis-
charge of the river, and also for occa-
sional excessive floods. A modification
of the system of wash lands, already
referred to, points to the method of
securing this end. The ordinary chan-
nel of a river should be of sufficient
capacity to take the normal flow of the
stream, the sides being made at as
steep a batter as the natural inclina-
tion of the soil would allow, and at
such a height as may be desirable for
retaining the water for the supply of
agricultural and domestic purposes or
water-power. The water being then re-
tained in as small a compass as possi-
ble, the weeds would be less likely to
grow and shoals to accumulate. The
sides beyond this should be laid at a
slope sufficiently flat to allow of the
growth of grass and the feeding of
sheep and cattle in summer, and the
protecting banks set sufficiently far back
to allow room for the passage of the

greatest floods likely to occur. Where
banks already exist, they would require
removing on one side at least, and
where there are no banks the material
dredged and cleaned out of the channel
would in many cases be sufficient to
form them. Bridges and other open-
ings must, of course, be adapted to
the flood discharge. By this means
provision would be secured for both or-
dinary and flood-water, without loss of
productive land, and the varying char-
acter of the discharge accommodated.

Where the channel passes through a
town, as the Witham at Boston, the
Welland at Spalding, and the Nene at
Wisbech, the difficulty of altering the
river is no doubt greatly enhanced ; but
it may be overcome in the manner pro-
posed by Mr. Abernethy for Wisbech, by
making an entirely new cut for the river,
and dockizing that portion of the old
river which passed through the town.
By this means the discharge of the<
floods would be provided for, and by re-
moving the ships from the channel
where they are always an obstruction in
floods, they would be enabled to lie and
discharge afloat in the dockized channel
of the old river at the existing granaries
and warehouses.

It may no doubt be urged that the ex-
pense of thus altering and adapting a
river to meet ordinary flood discharges
would be very great, but if the cost was
equitably spread over the whole water-
shed, the tax would not be greater than
the advantage gained.

In the upper reaches of the river much
flooding could be saved by dredging and
cleaning out the present channels, and
using the material in forming embank-
ments, provision being made for the lat-
eral drainage by soak dykes or drains
parallel with the embankments, and dis-
charging at a level sufficiently far down
the river.

REGULATION AND STORAGE OF THE WATER.

The regulation of the water requires
as much consideration as its discharge.
The greater rapidity with which the rain-
fall is now avoided leaves less to perco-
late through the soil for the supply of
wells, springs, and brooks. Flooding is
thus frequently followed by drought.
The level of the water in the soil is low-
ered below the depth at which it can rise

THE CONSERVANCY <>F BIVERS.

295

by capillary action to the roots of the
plants, the soil becomes parched, ami
tation languishes for want of moist-
ure, ami great inconvenience is experi-
enced from the failure of the water sup-
ply from wells and brooks.

In all river improvements the fact
should be kept steadily in view, that the
rainfall is only to be got rid of after
making due provision for water supply,
irrigation, water-power and navigation.
These are none of them incompatible
with good drainage. It is only neces-
sary that proper provision should be
inade by sluices and weirs for the dis-
charge of floods, and by side cuts or ar-
terial drains where the water has to be
held up so high that drainage cannot be
obtained for the ordinary discharge.

The value of holding up the water as
an aid in the cultivation of the soil is
fully recognized throughout the whole of
the Fens, as also in Holland. The water
in the main and subsidiary drains is
maintained in summer at a uniform level
of from 2 to 3 feet below the surface, by
a system of sluices with doors over which
any surplus flows, but which are drawn
immediately the supply exceeds the de-
mand, and the water is thus regulated to
a uniform level.

Water held up in a similar manner in
the higher levels would not only feed the
wells but afford power for the working
of the machinery of the farms through
which it traverses of a far more econom-
ical character than steam.

CONSERVANCY.

The administration of a river is hardly
an engineering matter; but it is a sub-
ject which seriously affects the carrying
out of any scheme of improvement.
One difficulty encountered by an engi-
neer is the restricted character of the
portion of the river he has to deal with.
He is called upon to devise a remedy
against flooding or other evils in a par-
ticular section of a river, the remedy for
which can only effectually be found by
dealing with portions beyond the juris-
diction of those who have sought his aid.
Attempts to bring the various bodies
having control over the river into har-
mony, in order to carry out one compre-
hensive scheme, almost invariably end in
failure from the diversity of interests.
Every local scheme is violently opposed

| by all other interests; and it has been
stated on reliable authority that the in-
ternecine feuds on the River N<'iic alone
during the last fifty years have cost
more than £100,000 in parliamentary and

j legal contests. The cost of obtaining

i the parliamentary powers necessary for
the improvement of the Ouse have
amounted during the past fifty years to
upwards of £150,000; and for parlia-
mentary proceedings alone for the Nene
Valley Acts over £30,000.

An engineer is thus frequently com-
pelled to design and execute partial
works on a section of the river at great
cost, where the same amount contributed
to a general improvement would have
effected tenfold advantage. '1 hus, on
the Witham, within the last few years, a
sum of nearly £50,000 has been expended
on the middle section of the river in

i deepening the channel and raising the
banks between Boston and Lincoln,
without any provision for increasing the
discharging power through Boston to
the sea, or relieving the lands above
Lincoln by enlarging the capacity of the
weirs and sluices. This was done in
spite of the protest of Sir John Hawk-
shaw that no effectual relief could be
given without extending the works
downwards to the outfall in the sea.
The consequence of this action has been
that the water is brought more rapidly
to the lower reaches without being pro-
vided with any increased means of es-
cape, and backs up the lateral drains,
bringing greater pressure on their banks
than they can bear. The floods have
been greater in this district since this
work was done than they ever were be-
fore.

It is only after repeated attempts,

i spread over the last eighty years, that
the various trusts below Lincoln have at
length united in a common scheme for
the improvement of the outfall from
Boston to the sea. Provision is also
about to be made for the better dis-
charge of the water from the river above
Boston, but even now this will give
little relief to the City of Lincoln and
the lands above.

The same process took place on the
Nene. A sum of £150,000 was spent
in improvements on a section of the
river between Wisbech and Peterbor-
ough; and the channel was lowered and

296

VAN NOSTRANIXS ENGINEERING MAGAZINE.

deepened without providing for the es-
cape of the water to the outfall, the
consequence being that the excavation
rapidly filled up, and, in spite of this
large expenditure and the consequent
heavy taxation, no benefit ensued.

In the attempt made a few years ago
by the corporation of Wisbech to carry
out the scheme for cutting off the
Horse Shoe bend through the town of
Wisbech — a plan which had been rec-
ommended by every engineer who had
reported on the matter for the last fifty
years — they were defeated by the op-
position of other interests in the river
each fearing some damage to the par-
ticular section of the river or interest
represented.

The number of private Acts of Parlia-
ment in force with relation to these four
rivers, even only where they pass
through the Fen land, is extraordinary.
The number of jurisdictions which have
control over the river or the banks has
accumulated till at times it is almost im-
possible to define their powers and
rights.

The whole history of the Fen land
drainage shows the baneful result of di-
vided administration, and teaches that
no voluntary or private legislation is
sufiicient. The administration of the
several districts protected by Fen Acts
is most efficient so far as it goes, and
some of the schemes in force may well
form a model for any Conservancy Act
that may be framed. To supersede ex-
isting organizations by new boards
elected on a different plan would be most
injudicious. What is wanted is a con-
solidation of all these smaller trusts, and
the uniting them by representatives sent
to one common Conservancy Board,
which should have control over the main
river and its banks from its source te
the sea, leaving the management of the
interior drainage to the trusts already-
in existence, or, where none exist, to
others formed under the powers of the
Land Drainage Act. Such a system
would cause as little disturbance with ex-
isting arrangements as is practicable
with an efficient system of conservancy
of the main outfall.

MODERN ARTILLERY.

From "Engineering."

The present moment, when a large
sum has been voted in the Budget for
the partial re-armament of our Navy
with guns of new type and of greater
power, seems a fitting one for discussing
those points of progress which have
rendered such a re-armament not only
desirable but necessary. The past four
or five years have led to an increase in
power of ordnance greatly exceeding
anything ever before achieved in a simi-
lar period. The question of breech-load-
ing versus muzzle-loading, certainly as far
as naval guns are concerned, has been
definitely decided in favor of the former
system; and the causes of the settle-
ment of this question, involving as it
does the total renewal of our naval arma-
ment, are not far to seek, and are inti-
mately associated with the increase in
power of which we have spoken above.

In this country Sir William Arm-
strong, and in Germany Krupp of Essen,
have taken the lead in progress. On

the questions of difference between these
great rival firms as to material and con-
struction we will speak later. The gen-
eral principles which have guided them
in their remarkable and successful en-
deavors to increase the powers of modern
ordnance may be briefly summed up as
follows : From the results obtained by
the Government Committee on Explo-
sives and the researches of Abel and No-
ble on fired gunpowder, it became ap-
parent that a high initial velocity of the
projectile, together with its attendant,
advantages of flatness of trajectory, ac-
curacy, power of penetration, and length,
of range could only be satisfactorily ob-
tained by generating in the bore of the
gun a large quantity of gas at low maxi-
mum tension or pressure. The produc-
tion of a large quantity of gas can only
be effected by using large charges of
powder. A reduction of the maximum
pressure may be secured by using either
very slow burning powder, which be_

MODERN ARTILLERY.

207

OOm6S converted into gas :it a niucli
lower rate than is the case with the pow-
der already is use; or by using the lat-
ter to reduce their destructive action by
allowing the charge to expand in a cham-
ber very much larger than is absolutely
Bsary to contain it. This latter
method is technically known as air spac-
ing. It is evident that a combination of
both these devices is possible. The im-
mediate result of the employment of
either or both is to necessitate the use of
very long guns, so as to keep the projec-
tile in the bore under the influence of the
propelling power of the gas for as long a
time as possible, thus counteracting or
more than counteracting the want of
high initial pressure. The whole result
may be described as follows: It has
been found possible by the use of very
slow burning powder, or of a quicker
burning powder duly air spaced, and ex-
panded in a very long bore to about
double the power of ordnance weight for
weight, and such a result does not seem
to point to any finality in the path of ar-
tillery progress.

Now, departing from mere theory and
passing on to the more practical applica-
tion of the principles enunciated above,
we find, broadly, that very similar results
have been arrived at with guns manu-
factured on the following systems :

(a) Built-up guns, all steel. Types —
Krupp, Yavasseur.

ib) Built-up arms of wrought iron
with steel tubes, such as the Armstrong
and Woolwich.

(c) Built-up guns with steel hoops and
tubes, but depending for their main
strength on steel wire of very high ulti-
mate strength, wound on cold. Types —
some French, American, and the Arm-
strong ribbon guns.

Before proceeding further we may say
that we have already decided the ques-
tion as to whether the gun should be a
breechloader or a muzzleloader, laying it
down as an axiom that our modern gun
must have great length of bore. This of
itself necessitates a breechloader. Ships
cannot be built, or existing forts cannot
be altered, in such a manner as to render
it possible to work a muzzleloader of the
length which is necessary to achieve the
ballistic results now attained. And here
we may clear the ground by observing
that breechloaders cannot be double-
Vol. XXVII.— No. 4—21.

loaded, as was claimed to be the case in
the melancholy catastrophe of the burst-
ing of the 38-tOD muzzleloader in the
fore turret of the Thunderer. A breech-
loader of the same size and weight as a
muzzleloader entails much less labor to
work than the latter; no sponging-out
is required; the gun can be loaded at
any position of training, and run out
the gun's crew are much better pro:
tected against the fire of shrapnel, ma-
chine guns, and rifles ; and finally, guns
of greater weight can be manipulated
by hand alone when loaded at the
breech than at the muzzle. Practically
it was found that in the case of the 38-
ton R. M. L. guns the limit of size ca-
pable of being worked by hand had
been reached, and complicated hydraulic
or steam gear to assist manual labor
became a necessity. In this country
breechloaders of 43 tons in weight have
been rapidly and easily worked by hand,
and abroad Krupp's 70-ton has given
equally satisfactory results. In fact, as
weight increased, the muzzleloader be-
came the more complex machine of the
two.

All these reasons are independent of
the great and paramount necessity for
breechloaders arising from great length
of gun.

Having decided then that our guns
are to be breechloaders, we pass on to
consider the question of their construc-
tion. It is a well-known fact that a
solid homogeneous cylinder subjected
to a heavy internal pressure, may be
destroyed by the interior layers of the
metal being strained above their ulti-
mate tenacity, while the outer are hardly
called on to do any work; this is more
especially the case with a suddenly ap-
plied pressure such as that exerted by
fired gunpowder. Hence arose the
method, first practically applied in this
country by Sir W. Armstrong, of put-
ting on the outer portions of the gun
! in a state of tension, and as a conse-
i quence the adoption of the built-up sys-
' terns of ordnance. This practice has
; become universal and has at present
reached its furthest development in the
l wire or ribbon guns above mentioned.

When one tube is placed over another,

the outer being in a state of tension,

it is evident that the inner must be in

' a state of compression varying with

298

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

the amount of tension to which the
outer is subjected and the relative thick-
ness of the two tubes.

Thus, a gun theoretically perfect to
withstand tangential or bursting press-
ure, should be built up of an indefinitely
large number of very thin coils or tubes,
each put on at such a tension that when
a certain pressure is set up in the bore
of the gun, the whole should be subjected
to exactly the same strain, thus utilizing
the strength of the material to the utmost.

Now, both theoretically and practically
the above state of things is exceedingly
difficult to arrive at. The earlier Arm-
strong guns had numerous very thin
coils, and over and above the great cost
of a structure built up in such a way, it
was very difficult to regulate the exact
amount of shrinkage to be given to each
coil. Instances, indeed, did occur where
the outer coils gave way without any dam-
age occurring to the interior of the gun.
The Woolwich system reduced the num-
ber of coils and thickened them, thus de-
parting further from our ideal standard.
Krupp first tried guns of steel cast in
one solid mass ; they naturally failed,
and he eventually approached more and

more to the methods adopted in this
country, without, however, ever abandon-
ing his material, viz., steel; Vavasseur
alone, as far as we are aware, of English
makers, following his example.

Modern experience tends to show the
soundness, both in theory and practice,
of the system of building up.

All ordnance now manufactured of any
great power consists of a steel tube sur-
rounded by either massive wrought-iron
coils, as in the Woolwich guns ; lighter
and more numerous coils, as in the Arm-
strong; steel tubes or hoops, as in the
Krupp; or steel wire and hoops, as in
the latest Armstrong. Even at Wool-
wich, the stronghold of wrought iron,
the superior merits of steel appear at
last to be acknowledged, and it seems
probable that, after a few years, the use
of wrought iron will gradually have dis-
appeared.

Of the different methods employed in
the above systems of providing for the
somewhat opposing demands for longi-
tudinal and tangential strength, and also
as to the qualities of the rival metals,
steel and wrought iron, we propose to
speak on another occasion.

PILE-DRIVING FORMULAS AND PRACTICE.

By RD. RANDOLPH, C.E.

Written for Van Nostrand's Engineering Magazine.

It is to be hoped that the directions
given by the Chief of Engineers to those
officers in charge of pile-driving opera-
tions for public buildings will have the
effect of establishing a more certain
guide for such work than the fallacious
and conflicting formulas to be found in
the text-books, and to which attention
has lately been called by the article in the
July number of Van Nostrand's Maga-
zine.

Whatever coefficients may be deter-
mined from these experiments, the form-
ulas otherwise must depend upon a
true theoretical deduction ; and it is im-
portant that those who are to determine
them see very clearly the truth of the
theory before applying the coefficients as
factors ; not as Col. Comstock advises,

" to take some good formula such as
Kankine's," selected from the general as-
sortment, perhaps upon the scientific
standing of the authority, or because it
has heretofore been generally adopted.

From the fact that Col. Mason did not
determine his formula until after com:
pletirig the work at Fort Montgomery, it
might be inferred that it was the result
of his experience, but as the build-
ings have settled since it is evident that
he did not have sufficient time to test
practically its truth. But the Mason
formula is the same as that of Weisbach,
which is derived from purely theoretical
considerations, and which falsely assumes
that the resistance to the penetration of
a pile is of the same character as that of
the resistance of gravitation to a pro-

PILE-DRIVING FORMULAS AND PRACTICE.

21)9

jectilc In vacuo; and that the path de- 1
scribed with an equal initial velocity
against either, will be in proportion to
the intensity of resistance to each particle
of the mase

By this assumption the inertia over-
come by the pile while penetrating the
mass of the earth, a force which increases
with the velocity, is completely ignored.
This can be proved by the formula itself ;
and for the purpose take tins illustration.
Suppose the pile to encounter at a dis-
tance from the surface another pile in the
same vertical line, placed there by some
pre-historic race, thus forming a continu-
ous pile of greater length. The last
blows of the hammer might cause an uni-
form penetration which would be used
in the formula ; but the application of it
now would give the pile credit for sup-
porting a greater weight than would be
true, because one of the factors, the
pile, has not been fully estimated. The
unknown portion of the pile has ab-
sorbed the momentum of the hammer
just as has the known portion of it. Al-
though in practice such a case may never
occur, yet there is always a mass of earth
to be driven down, or laterally from the
sides, and waves of concussion to be sent
through the earth in all directions ; an
effect increasing with the velocity and
generating the resistance of inertia, but
unlike the hidden pile, it does not apply
the momentum absorbed to the penetra-
tion.

In order to show the effect of ignoring
the hidden pile let us apply a formula
which ignores the inertia of both, as
Rankine does. When the hammer falls
from the height F, according to the
well-established law of falling bodies, its
velocity at the point of impact is

wise if let fall from the height of />, under
the influence of the same force, its veloc-
ity at the end of /> would be a/2Fx \/g.
As the accumiiiulated effect of one
second's duration of actual gravitation
is a velocity represented by g, let that of
the resistance to the hammer be repre-
sented by x. Then, by the same law,

\f2px\/x is the velocity acquired or
overcome, as the case may be, in the dis-
tance p, which we have seen is V2Fx
aA/. This gives the equation

V2p X a/sc= a/2F X Vg

F.r/

which reduces to x = —L-. The intensity of

p j

the two forces being in proportion to the

F.?

two velocities g. and — -, acquired in the

same time, their ratio is - ; and the pile

p i

will resist - times as much force as is

P
offered to the hammer by actual gravita-
tion, which is its weight, denoted by W.

W.F

It will therefore sustain lbs. In the

example at Proctorville, mentioned by

Gen'l Weitzel, this would be nn •-

.03125

= 142400 lbs., a result nearly reached by
Rankine's formula.

But now supply the omission and in-
clude the pile, as is done in Weisbach's
formula. The velocity of the hammer is
the same as before a/2F x Vg, but be-
fore the penetration begins, and at the
moment of impact, its momentum is ap-
i plied to both masses, and they move with
a common velocity which is proportion-
ably less ; and is expressed by

X/7=a/2FxV#.

Now assume that the resistance to the
further descent of the hammer is a force
uniformly distributed, not through space,
but through time, like that of gravita-
tion, and which brings it to rest in a
distance equal to the penetration denoted
by p. If gravitation could be so magni-
fied as to give that much resistance to
the mass of the hammer, it would not
ascend higher than p, although protected

with a velocity of \/2FxVg. Like-

V2FxVgx

W + w

in which w represents the pile. The
equation now becomes

*j2p x ^/x= a/2F xVgX

W + w'

F.r/. W2

which reduces to x = -== -r, , this

p. (W + w)

F.W2

divided by ogives the ratio of

p.(W + u>y

330

van nostrand's engineering magazine.

and the resistance to the pile is equal to
that many times the force of gravitation
on hammer and pile, i. e., their weight.
Multiply this ratio by W + 10 and we have

F. W2

— — ; which is the weight to be

p . W + \o

supported by the pile according to Weis-
bach. In Gen'l Weitzel's example this

5 9102

would be T03125X910 + 16li = 52557-

In both cases the masses were sup-
posed to be resisted by an uniform force
which in equal small divisions of time
subtracted equal amounts of velocity,
and that the paths described were the
measures of the intensity of the resist-
ance to each particle of the mass when
referred to one due to the same initial
velocity. Knowing the initial velocity of
each and referring to the path that would
be described if projected against gravi-
tation with the same initial velocity, the
relative intensity of the resistance in
each case to that of gravitation was ob-
tained ; which being applied to the quan-
tity of each mass determined the resist-
ance in terms of gravitation. But as the
paths are in proportion to the square of
the initial velocities which produce them,
the resistance to each particle is in the
same proportion. Therefore the resist-
ances are respectively in proportion to the
square of the velocity multiplied by the
mass ; which accounts for the difference
in the results. Diminished velocity does
not compensate for a proportionate in-
crease of mass.

This proves that the Weisbach for-
mula, or any other which is deduced
from the law of falling bodies, cannot be
applied unless all the elements of inertia
are represented and the velocity of pene-
tration modified accordingly. We have
seen the effect of omitting the pile, and
can therefore appreciate the effect of
omitting the hidden pile which the for-
mula would not reach ; and in the same
manner we may comprehend the great
variety of mass put in motion at every
blow of the hammer and which no
figures could fully express. And we can
understand that most of this motion is
wasted in producing other mechanical
effects than contributing to the penetra-
tion of the pile.

So far has been considered only masses
which share the momentum of the ham-

mer before the commencement of the
observed penetration ; but such mass
may be infinitely subdivided and uni-
formly distributed along the path of the
penetrating body like the particles of a
fluid. But in the same way the mo-
mentum may be divided into elements,
each having its initial velocity to be
affected in the manner observed in the
case of the integer. Such a resistance
may be resolved into elements of pure
impact, which would show it to be in
proportion to the square of the velocity.
For the sake of illustration, suppose two
locomotives to be running on parallel
lines, one at double the velocity of the
other, and they encounter a long drove
of cattle standing equi-distant upon the
track — the resistance to the first will
be four times that to the second;
because in the same space of time it col-
lides with twice the number of objects
and hurls them all with double the ve-
locity. Instead of masses suppose the
obstructions to be cords so light in
proportion to their strength as to be de-
void of inertia — the resistance to the first
would be twice that to the second, be-
cause it would depend solely upon the
number broken in a certain time. But
suppose these latter to be equi-distant in
time instead of space, the resistance
would be equal to both locomotives, as
they would encounter the same number
in the same time. When the pile driver
has to overcome a resistance like the
last, a formula derived from the law of
falling bodies can be applied. But when
it is of a character of the two first, it
must be so modified as to represent the
relations of the elements of mass and
velocity.

It is also to be noted that two quan-
tities have been neglected in the Weis-
bach formula ; one of them is small
enough to be neglected, but the other
has been recognized by Rankine. The
first is the action of gravitation during
the penetration which counterbalanced
the resistance to that extent. This
would require that the weight of the
hammer should be added to the indicated
load to be supported, as that does not
remain with the pile. The second is the
compression of the pile, which is a part
of the penetration applicable to the
hammer, while the observed penetration
is applicable to both.

PILE-DRIVING FORMULAS AND PRACTICE.

301

In the formula of Rankine this com-
pression and the observed penetration
are both applied to the hammer alone, as
the pile is entirely ignored otherwise.
The whole movement is supposed to be
resisted by the friction of the earth along
the sides of the pile ; and all resistance
to be independent of velocity. Thus
differing from Wiesbaoh only in this,
that the Latter neglects elements of in-
ertia that are not apparent, while Ran-
kine neglects those that are apparent
and great in quantity.

The example mentioned by Col. Tower
will illustrate this error on an exaggerated
scale. He supposes a heavy target sus-
pended like a ballistic pendulum. If we
press against it with the hand we will,
under that slow movement, encounter
only the resistance of friction at the point
of suspension and a very slight effect of
its gravity when pushed beyond the
vertical. Now if a shot be fired through
the target, does that shot have no other
resistance than the friction at the point
of suspension and gravitation along the
very small arc through which the target
moves, and which just before was over
come by the pressure of the hand 1 Or
was not the inertia developed by the high
velocity of the projectile so great, that
it was easier to tear away the solid metal
than to overcome it to any considerable
extent? So the compression of the pile
is due to its own inertia developed by the
velocity of the hammer, as well as the
resistance of the earth behind it; the
latter becoming less in comparison as
the fall of the hammer or weight of the
pile is increased.

In his "Applied Mechanics," Professor
Rankine gives a formula for pile driving
which results in a smaller quantity than
the one given in his work on "Engineer-
ing," the difference being due to the
modulus of elasticity being applied to
one-half the length of the pile in the
first and one-quarter of the length in the
second. In order to see the elements
considered, let us trace the process
through which the formula is reached.
The hammer being the only mass con-

compression of the pile, and which we
will call c. This will give W . F . =
R.^> 4- R . c. As the modulus of elas-
ticity, denoted by e, will compress one
square inch of the sectional area of the
pile, denoted by 0, its whole length,

denoted by I ; R will compress it - of its

length, or

e
whole area only

; but will compress the

— - ; which is the value
e. s

sidered we have, as before,

W.F

= R, or

W.F=B./J, denoting by R the resistance
or the weight to be supported. The
penetration is now increased by the

of c. But as the resistance is consid-
ered as distributed along the whole
length, and not at one end, the com-
pression will diminish from the full
I quantity at the top to zero at the bottom
I uniformly, and will amount to. one-half
! of the full quantity for the whole length.
In which case the value of c becomes

=~- . By substituting this in the equa-
tion, it becomes

TTT _, ,.„ R .1 R2
W.F = K.2? + s— ors—

A.e.s 2.e.s

R.p W.F

RJ + R.

2p.e.s 2W.F.e.s

Complete the square of the first member
of the equation by adding the square of
one-half the coefficient of R in its second
term to both members.

R2 + R

2.p.e.s

p\e\s>

2W.F.e.5

Then extract the square root of both
members,

R +

p.e.s ./% W.F. e. s p*.e*

V-

2W;F.g.g
I

p\e\a%

p.e.s

which is Rankine's formula in " Applied
Mechanics." But in his "Engineering,"
for some reason which he does not state,
he considers the compression as appli-
cable to only one-fourth of the length of
the pile ; making the value of c in the

R /
above -t— - which changes the final equa-

4.e.5

tion to

302

VAN TS"OSTRANDS ENGINEERING MAGAZINE.

R = Y ; +

2p.e.s

Taking the same modulus of elasticity
for both, 750 tons, or 1,680,000 lbs., and
the other data in the example of General
Weitzel, J=30, s=138.25. the indicated
resistance by the first is 117,208 lbs., and
by the second 128,530 lbs.

It will be seen that the only difference
between these formulas and the one first

suggested, K:

W.F.
P

, is the increasing

the penetration by the extent of com-
pression, and the effect of this is seen by
comparing their results with that of the
latter, which, with the same data, was
142,400 lbs.

The Weisbach formula depends upon
the assumption that at the instant of
contact the hammer and pile were en-
dowed with a common velocity due to
their combined masses ; which could
not be the case if the pile undergoes com-
pression ; for the hammer would move
faster and the pile slower than this until
the compression ended, the momentum of
the two masses being the variable parts
of a constant sum.

But the initial velocity of the penetra-
tion is less and combined with a less
mass, since the momentum of the ham-
mer is not all applied until the compres-
sion is exhausted. The addition of the
whole mass during the penetration will
compensate for its deficiency in the be-
ginning, as far as momentum is con-
cerned ; but as time has been lost in its
application, the deficiency of velocity in
the beginning is not compensated for, as
far as this effects penetration ; for, ac-
cording to the theory upon which both
formulas are based, the resistance is dis-
tributed uniformly in time like that of
gravitation — not uniformly in space.
The penetration will therefore be less
than that due to the assumed condition
of inelasticity ; and this will be assigned
to greater resistance instead of less ve-
locity. Any correction then, on account
of compression of the pile, will diminish
the result of the formula and take it
still further from that of Rankine.

If all the elements of inertia could be
as easily ascertained as the principal one,
the inelastic pile, it would only be neces-
sary to add the mass representing it to

the pile in the formula of Weisbach.
And perhaps experiments may determine
the value of this quantity for different
situations. But a very simple experi-
ment will determine whether it can be
correctly applied without this addition.
Let the fall of the hammer be so adjusted
that the initial velocity of hammer and
pile in one case may be double that of
another. If the penetration in the first
is four times that of the second, it will
prove that the law of falling bodies can
be applied, otherwise not.

If it were true that the piles are sup-
ported only by the friction against their
sides, each cluster would have to be con-
sidered as one pile, and the surface of
the cluster would represent the resist-
ance. Also the weight of the cluster
would have to include the intervening
material ; for being cut off from terra
ftrma, it would be supported by the
piles alone. But this would imply that
the base of the pile-work was a fluid
which would receive the pressure, or a
part of it, if the lateral friction was in-
sufficient; and would yield, however
slowly, until an equilibrium was estab-
lished. It has been observed that sheets
of ]ead that have remained for centuries
upon the steep roofs of ancient buildings
are very decidedly thicker at the lower
edge than the upper ; from which it is
inferred that the flow of cold lead, like
the flow of the glacier, is only a question
of time. So that any test which might
be made by placing a load upon a pile
that has been driven, would fail to indi-
cate, in the limited period at the disposal
of the engineer, the extent to which it
might yield after the lapse of years.

But however fluid the pile foundation
may be, it can develop inertia under
velocity which would completely falsify
a formula which ignores that element —
altogether absent in the case of a qui-
escent load.

A New Variety of Glass. — The Wiener
Oewerbe-Zeitnng states that a chemist of Vienna
has invented a new kind of glass, which con-
tains no silex, potash, soda, lime, nor borax.
In appearance it is equal to the common crystal,
but more brilliant ; it is perfectly transparent,
white and clear, and can be cut and polished.
It is completely insoluble in water and is not
attacked by fluoric acid, but it can be corroded
by hydrochloric and nitric acid. When in a
state of fusion it adheres to iron bronze and
zinc. — Oaceta Industrial.

SUBSOALES, OCCLUDING VERNIERS.

303

SUBSCALES, INCLUDING VERNIERS.

By II. II. LUDLOW, 2d Lieut. 3d Artillery, U.S.A.
Contributed to Van Nostrand's Engineering Magazine.

SUBSCALES IN GENERAL.

1. Measurement of distance is the de-
termination of a required distance by
comparing it with some known distance
called the unit of measure. This com-
parison may be effected by successively
applying the unit to the required dis-
tance, until the remainder is less than
the unit. The remainder is then neg-
lected altogether or considered as an ad-
ditiomil unit, according as it is or is not
less than half the unit. If a more nearly
exact result is desired, a smaller unit of I
measure must be taken. This may be
done, either by taking a smaller unit in
place of the one first used and beginning
the measurement anew; or, better, by
treating the unit first taken as a collec-
tion of new units, simply measuring the
remainder in terms of the secondary unit
which should exactly divide the primary.
In like manner remainders from the sec-
ondary unit may be measured in terms
of a tertiary unit, k.o,. The smallest unit
taken in any system of measurement is
called the ultimate unit.

2. Standard distances for the measure-
ment of other distances have been adopted
and named, as an inch, a yard, a meter,
<fcc. These are necessary to express a
distance conveniently. They may or may
not be the primary, secondary, &c, units
of measure actually applied, and may be
called for distinction units of expression.

3. For convenience, scales are fre-
quently formed by the successive appli-
cation of the unit along a line, so that
any distance shorter than the scale may
be measured at a single application. For
distances longer than the scale, the whole
scale may be applied as a primary unit of
measure, the unit on the scale becoming
secondary. The least space on the scale
used is ordinarily taken as the ultimate
unit of measure, but frequently it is
taken as a primary unit, with a smaller
ultimate unit. An auxiliary scale is then

needed to measure1 the remainders from
the primary unit, and if applied directly -
to the main scale and along3 it, the aux-
iliary scale is called a subscale. Hence :

4. A subscale is an auxiliary scale of
equal parts, directly applied along a main
scale of equal parts: for measuring all
distances along the latter, taking the
least space on the main scale as a primary
unit, with a smaller secondary unit. The
least space on the main scale is called the
scale space ; that on the subscale, the sub-
scale space. The secondary unit is called
the least count.

5. When a division of the subscale is
directly opposite a division of the scale,
so that the two form one continuous line,
the subscale division is said to coincide,
and is called a coincident division.

6. In measurement two divisions are
taken, one on each scale, and the distance
between them made equal to that to be
measured. The distance is then deter-
mined by a coincident division. In exact
measurement a coincident division must
exist, and the sum or difference of two
distances, one on each scale, measured
from it, will give the required distance.
Every common aliquot part of the scale
and subscale spaces exactly divides this
sum or difference ; and no distance thus
exactly measurable can be less than their
greatest common aliquot part.

7. All distances exactly measurable by
this combination alone,4 must, §4, be ca-
pable of exact expression in terms of the
secondary unit. But they may also be ex-

1 The remainders may be estimated by con-
ceiving the least space on the scale to be sub-
divided, but this is not in general reliable.

2 As an illustration of indirect application,
may be mentioned the scale on the head of a
screw for measurement along the axis.

3 The diagonal sliding scale is directly ap-
plied, but not along the main scale.

4 If a tertiary unit were used, it would re-
quire, beside the scale and subscale, either an
additional device for measurement or supple-
mentary estimation.

304

VAN NOSTRAND 8 ENGINEERING MAGAZINE.

pressed, § 6, in scale and subscale spaces*
The secondary unit or least count must
then exactly divide the subscale space as
well as the scale space,5 and cannot ex-
ceed their greatest common aliquot part.
Nor can it be less than this part since it
is exactly measurable by the combination.
Hence, the least count is equal to the
greatest common aliquot part of the scale
space and the subscale space.

8. That each subscale division may in
turn be coincident and opposite any scale
division, the dividing lines on both scales
must all intersect the line along which
the scales meet. That the subscale shall
always measure along the scale, the two
scales must accurately fit each other, how-
ever placed, which condition limits the
possible shapes of scale and subscale, in
a plane, to the straight line aad arc of a
circle.

9. Relations of subscale elements. —
Those quantities which are always the
same for the same scale and subscale
are called subscale elements. In any
scale and subscale, denote by I, a, b, the
least count, scale space, and subscale space
respectively; then, § 7,

i=*.

(!)•

(2).

qb=qa (3).

in which q and q' are whole numbers mu-
tually prime, and </>l since l<.a, § 4.

Since the least count is the secondary
unit, it is less, § 4, than the scale space.
It must then, § 6, be the difference of two
distances, one on each scale. Let r, r'\
denote the least numbers of subscale and
scale spaces respectively that can differ
differ by I. Then,

±l=r'a—rb.

(4).

Divide both numbers by I and reduce by
(1) and (2), then

±l=r'q— rq' (5).

r and / are integers, also r'q and rq' are

5 This requires two commensurable scales.
If incommensurable scales were used, no unit
secondary to the scale space could exactly ex-
press all the distances exactly measured. The
auxiliary scale would not be a subscale, § 4, and
the combination would be very inconvenient.

mutually prime, their difference being
unity; r' and q are each prime with re-
spect to both q' and r, r cannot be o,
since that would require q=l.
I, a, by q, q, r, r' are subscale elements.

10. From equation (3) since q and q'
are mutually prime:

1°. In every subscale q is the least
number of subscale spaces that can
exactly cover a number of scale
spaces; and q' the least number of
scale spaces that can be exactly cov-
ered by a number of subscale spaces.

2°. If any subscale division coin-
cide, § 5, those subscale divisions sep-
arated from it by q, 2q, Sq, &c, sub-
scale spaces, and those only will also
coincide.

3°. If any subscale division fails
to coincide with the nearest scale di-
vision by a given distance, the sub-
scale divisions separated from it by
q, 2q, Sq, &c, subscale spaces, will
each fail to coincide with its nearest
scale division by the same distance
estimated in the same direction.

11. If r and r are known, q' may be
eliminated from (2) by (5) leaving in (1)
and (2) four elements, any two of which
will determine the others.

If r and r' are unknown, it will be
shown § 43 that (5) suffices to determine
them when the other elements are known.
Ignoring r and r', (1) and (2) are inde-
pendent equations, containing the five
elements I, a, b, q, q', any three of which
will determine the other two, provided
the given quantities do not all enter the
same equation. If I is given with a or b
it must, § 7, be an aliquot part of each. In
one case two quantities, a and b, suffice,
owing to the fact that q and q' are mutu-

q a
ally prime; for (3) may be written — =r»

which in its simplest form gives both q
and q.

12. Classification. — Subscales are clas-
sified according to the relations between
scale space- and subscale space, as simple,
vernier, and complex subscales, §§ 21, 26,
42. A subscale is direct when, of the
least scale and subscale distances (4) dif-
fering by I, the greater is on the scale ;
retrograde when the greater is on the
subscale.

13. Subscales are further classified ac-
cording to their extent. A complete sub-

SUfcSOALES, l\cl.ri)lN(; VERNIERS.

805

scale is equal in length to the distance
on the indefinite subscale, from any co-
incident, § 5, division to the next coinci-
dent one, A subscale of less extent is
incomplete; of greater extent, redundant.

14. A complete subscale contains just q
spaces, § 10, 1°. Redundant spaces are each
separated by q, or 2y, or 3q, &c., spaces
from some division among the first q ; and
those of each set of corresponding di-
visions, % 10, 2°, 3°, are like situated for
coincidence. Measurements with sub-
scale are based, § 6, on coincident di-
visions. Hence, redundant divisions do
not in general increase the efficiency of a
complete subscale. In any complete sub-
scale we see (1) that the least count is
equal to the scale space divided by the
aiti)\ number of subscale S2)aces.

15. To decide whether a given subscale
is redundant, complete, or incomplete, the
definition may be directly applied, or the
entire number of spaces may be com-
pared with q if known . When the second
coincidence exists, q and q' may be found
by direct observation, § 10, 2°.

16. Measurement with scale and sub-
scale consists of two parts : 1st. Adjust-
ment, so that the required distance shall
be equal to that along the scale from a
division, usually the zero, to the zero
division of the subscale. *2d. The read-
ing, i. e., finding the distance by inspect-
ing6 the adjusted scales.

17. Adjustment. — 1st. The scale should
be in such a position along the line of the
required distance that its zero will be at
one extremity of that distance. As the
scale must keep this position throughout
the measurement, it should, if practicable,
be firmly fastened. 2d. The subscale
should be in such a position along the
scale that its zero will be at the other
extremity of that distance. Accurate ad-
justment is usually effected by a rack and
pinion, or by a clamp and screw device.

18. Heading. — The result of the act of
reading is called the final reading. It
expresses the distance from the scale zero
to the subscale zero, and is composed of
two parts, called the scale reading and
subscalj reading, and determined from
the numbers on the scale and subscale
respectively. The scale reading expresses
the distance along the scale from its zero

6 A simple inspection is sufficient to deter-
mine the measurement, if the subscale is prop-
erly numbered.

division to the division of reference
the scale division to which the position
of the subscale is referred. The subscale
reading expresses the distance from the
division of reference to the zero of the
subscale.

For convenience the division of refer-
ence is so taken that the final reading
shall always be equal to the arithmetical
sum of the scale reading and subscale
reading.

19. Let AD, Fig. 1, represent any scale
wTith its zero at A, and let V be the
position of the subscale zero after ad-
justment.

Fig.1 v

The method of coincident divisions ? 5
having been adopted, § 6, some division
of the subscale must be coincident or be
(provided the least count is to be the
ultimate unit of measure) considered co-
incident with a scale division. The di-
vision which most nearly coincides is con-
sidered coincident.7 If V is considered
coincident let C be the corresponding
scale division. C is then the division of
reference, and we have subscale reading
= o, scale reading == AC = final reading.
If V is not considered coincident, let V
lie between the consecutive scale di-
visions C and D. C lying on the side of
the lesser numbers of the scale is then
taken as the division of reference,8 and
we have scale reading = AC, subscale
reading =CV, final reading = AV= AC 4-
CV. The subscale reading, CV, is then
differently determined for the different
classes of subscales.

20. If CV (Fig. 1) is determined di-
rectly from it, the subscale is said to be
forward arranged; if indirectly from the
relation. CV = CD — VD, backward ar-
ranged. °

7 Compare note 4.

8 D might have been taken as the division
of reference. Then AV^AD - VD. This
is inconvenient as the scale reading AD
would have to be diminished by the subtrac-
tion and could not be at once written as a part
of the final reading.

9 The terms forward and backirard arranged
were first applied to verniers according to the
direction in which it measures its own small
motions, as compared with that of increasing
scale measurements. See § 28.

306

van nostrand's engineering magazine.

SIMPLE SUBSCALES.

21. A simple sitbscale is one in which
the subscale space exactly divides the
scale space.

22. For simple subscales we have, § 7,

l=b

(6).

which in (4) requires r=l, r'=o, giving
in (5)

2'=1 .... (7).

a relation which also results from com-
paring (6) with (2). r and r' being
known the other elements may be found
as in § 11.

23. For measurement, the subscale
zero should, according to § 16, be at the
extremity of the required distance. But
ordinarily a simple subscale is detached,
and is used as may be most convenient.
It is merely a scale of finer subdivision
than the main scale, for measuring di-
rectly the distance from the extremity
of the required distance to either of the
two consecutive scale divisions between
which that extremity lies. One of these
consecutive scale divisions is the division
of reference. Direct measurement to it
corresponds to forward arrangement ;
direct measurement to the other scale
division to backward arrangement.

24. Whether a simple subscale is re-
dundant complete or incomplete may be
decided as in § 15. Practically it is only
necessary to compare its entire length
with a scale space. If incomplete, it is
too short to measure directly all frac-
tional parts of the scale space. But it
may be used whenever it is as long as
half the main scale unit.

25. The simple subscale is inconveni-
ent when the least count is very small,
as the spaces may be too small for dis-
tinct vision.

VERNIER SUBSCALES.

26. A vernier subscale or vernier (so
called from its inventor, Pierre Vernier of
Brussels, A. D. 1631), is a subscale, in
which the difference of scale and sub-
scale spaces exactly divides the scale
space.

27. The difference of vernier and scale
spaces is their greatest common aliquot
part, which fact requires, § 7,

giving in (4) r=l, r'=l, and reducing

(5) to

±l = q-q' . . . (9).

A vernier is direct or retrograde, § 12,
according as a>b or a<b.

Solving (9) with respect to q', we see,
§ 10, that :

Every complete vernier covers q ^ 1
scale spaces according as it is direct or
retrograde, r and r' being known, the
other elements may be found as in §
11.

28. Beading. Let AE (Fig. 2) be any
scale VW any accompanying complete
vernier. Resume the notation of § 9 and
27. Denote the vernier reading by x.
Let the consecutive vernier divisions be
numbered 0, 1, 2, 3, &c. to q beginning

Fig.2

1 1 1

±l=a-b

(8).

with V, which is supposed coincident
with some scale division C. Since I is
numerically equal to a— b, § 27, the ver-
nier divisions numbered 1, 2, 3, &c. to q
will fail to coincide with the correspond-
ing scale divisions by I, 21, 31, &c, to ql
= a. If the vernier be now moved in
such a direction that the vernier division
numbered 1 will at the outset approach
its corresponding scale division, vernier
divisions 1, 2, &c, will in succession co-
incide, § 5, and thereby measure the
distances I, 21, &c, passed over by the
vernier zero V. If at positions inter-
mediate to those of exact coincidence the
most nearly coincident vernier division
is taken as coincident, the error cannot

exceed ^. This gives the required meas-
ly

urement in all cases to the nearest unit
with l as the unit of measure. The dis-
tance thus directly measured is that
from the scale division C to the vernier
zero Y in the position read, estimated
in the direction of the supposed motion.
If this motion is in the direction of in-
creasing scale numbers, C is the division
of reference, § 19, for the position read,
the vernier is forward arranged, § 20,
and we have

x~nl

(10)

SUBSCALES, INCLUDING VERNIERS.

307

If this motion is in the direction of
decreasing scale numbers, the division of
reference is the scale division next to C
on the side of the lesser scale numbers,
the vernier is backward arranged* and
we have

;c=a—n!=(q — ?i)l

(u).

In both (10) and (11) n denotes the
number of the coincident vernier di-
vision.

29. Forward and backward arrange-
nt. — If the vernier is direct, its spaces

are smaller than the scale spaces, and
the above-supposed motion is in the di-
rection of increasing vernier numbers.
A direct vernier, § 12, will then be for-
ward arranged if its numbers increase
in the same direction as the scale num-
bers ; and backward arranged if they in-
crease in a contrary direction. In like
manner it maybe shown that a retrograde
vernier is backward arranged if its num-
bers increase in the direction of increas-
ing scale numbers, forward arranged if
they increase in the contrary direction.

30. The vernier zero is naturally taken
at one of the extreme divisions, but in a
complete vernier the zero may be at any
intermediate division. It is only neces-
sary that the divisions preceding the
zero division shall be marked with the
same numbers that they would have, if
removed bodily and j^laced as redundant
spaces at the end of the vernier. For
any one of them can coincide, § 5, only
when the corresponding redundant di-
vision coincides, § 10, 1°. 'J his requires
that the number on the last division
shall be repeated on the initial division,
after which the numbers increase in the
same direction and by the same law as
before.

31. Measurement. — The vernier is
ordinarily forward arranged, for which
arrangement the important steps in
measurement are summarized in the fol-
lowing

RULE.

Adjustment. — The scaie and vernier
should be in such positions that the re-
quired distance shall be equal to that
along the scale from its zero to the ver-
nier zero, § 17.

Reading. — 1st. If the vernier zero is
considered coincident, § 5, read the' cor-

responding scale division for the final
reading, § 19.

2d. If the vernier zero is not con-
sidered coincident, § 19, read for the
scale riading the division of the scale
next to the vernier zero on the side of
the lesser numbers of the scale. Then
multiply the number of the vernier di-
vision considered coincident by the lea si
count for the vernier reading ; add the
vernier reading to the scale reading for
the final reading.

32. If the vernier is backward ar-
ranged, the vernier reading as found in
the above rule must be replaced (11) by
the remainder after subtracting it from
the scale space.

33. Many verniers are marked with
the numerical values of /, 21, &c, to ql
on the 1st, 2d, &c, to qth divisions,
thereby avoiding the multiplication in
the application of the rule. Frequently
also intermediate numbers are omitted,
and divisions at regular intervals only
are numbered.

34. There is difficulty in finding the
most nearly coincident vernier division,
when I is less than the width of the lines
on the instrument. Thus if the nth. ver-
nier division coincides exactly, the (n +
l)th appears also coincident, and so on
in both directions until the difference be-
comes perceptible. The nth division is
then the middle one of those apparently
coincident, and their number is odd.

In reading such a vernier, take as co-
incident the middle one of the coincident
divisions ; if their number is even, either
of the two middle ones may be taken

with an approximate error1 ° of -. With

such a vernier a lens is frequently used
to aid the eye, and a few redundant
spaces are generally added at each end,
so as not to diminish the number of con-
secutive coincident divisions, when the
reading is near the end. The extremities
of the vernier proper are then plainly
marked.

10 Whenever two consecutive vernier di-
visions are equally near to coincidence, the

lesser reading may be taken, and - added, thus

rendering the result more nearly exact. Judg-
ment might be further used to estimate a frac-
tional part of I, but it is in general unreli-
able.

308

VAN NOSTRAND7S ENGINEERING MAGAZINE.

35. If the vernier is redundant or
complete, the nth division considered co-
incident always exists since n < q, § 28.
If the vernier is incomplete, the nth ver-
nier division may be beyond its limits.
Such a vernier is inconvenient for use.
It is possible to use such a vernier, pro-

q
vided it contains at least | spaces, but

it must be forward arranged when the

vernier reading is less, and backward

arranged when greater than ^.

36. Classification. — To determine
whether a given subscale is or is not a
vernier,11 we have (9) which is more
convenient than the direct application of
the definition, § 26, when q and q' have
been determined. If the subscale is
known to be complete, § 13 and 27, it
must, if a vernier, cover just one more
or one less scale space than its own
number of spaces, which fact is decisive
and can be observed directly.

The condition for a direct vernier, §
27, is a>b or q>q'\ for a retrograde
vernier a<b or q<q'. Either form of
the condition may be us*ed according to
the elements already determined. In
practice the first form is the more con-
venient, and whether a > or < b may be di-
rectly observed. If I is very small, it
may be necessary to look along the scale
and vernier from the coincident division,
until the aggregate difference is percept-
ible ; if the greater aggregate distance is
on the scale, na > nb or a > b ; if the
lesser distance is on the scale a<J>.

37. Single, double, doable folded. — A
single vernier is a complete vernier bear-
ing on its divisions but one set of num-
bers (see § 38, 39).

Some main scales have the zero at an
intermediate division, the numbers in-
creasing in contrary directions from it.
If a single vernier is forward arranged
on one part, it will, § 29, be backward ar-
ranged on the other part. If one part is
short and used only in detecting instru-
mental errors, the vernier is forward ar-
ranged for the longer part, and the
shorter part is called the scale of excess.
If both parts are to be used in measure-

ii if a—b= -. 5—- and the subscale is at the

4i a

same time a simple subscale and a vernier. It
may he used either way.

ments, backward arrangement is gener-
ally avoided by using two single verniers
on opposite sides of a common zero,
one for each part. The two verniers
united form a double vernier (see §
40).

The same result, of double reading
may be attained with but one vernier,
by giving on the same lines of division
two sets of numbers increasing in oppo-
site directions. A n intermediate division,
usually the middle one, is taken as the
common zero of both sets of numbers
which are arranged as explained in §
30. Such a vernier is called a double
folded vernier (see § 41). It is more
compact than the double vernier.

38. Illustrations. — One of the simplest
of single verniers is represented in Fig.
3. The scale space is y-J-g- ft., and 10
vernier spaces cover exactly 9 scale

Fig.3

spaces. The numbers on the scale cor-
respond to tenths of a foot, and" the
part represented is supposed to lie be-
tween 4 and 5 ft. It is forward arranged,
direct, and reads 4.867 ft. This is like
the vernier on the "New York " leveling
rod.

39. The vernier of the ordinary cistern
barometer is represented in Fig. 4. The
scale space is -£$ inch, and 25 vernier
spaces exactly cover 24 scale spaces,
giving a direct vernier whose least count

is inhr m- 5J = Tjj-g- in. :
every fifth vernier division,

10 0

in.

and

33, is num-

SUBSCALES, [NOLUDING VERNIERS.

309

bered. The vernier is forward arranged,
arid the third vernier division after the
one numbered 1 is coincident. It reads
29.G0 + .01 + 3 X. 002 = 29.616.

The most common errors are to omit
the first adjustment, § 17 ; and in read-
ing to neglect one of the least spaces on
the main scale, when the scale division
read is not an even tenth of an inch.

least count is 1'. There are two sets of
numbers, each increasing from 0 to 15 at
one end, and then from 15 at the other
end to the middle division. The division
numbered 7 and 23 coincides. The read-
ing is 1° 7', 7 being the set of numbers
giving forward arrangement, § 29. Such
a vernier is in use on the vernier com-
pass by W. and L. E. Gurley.

Fig.4

Fig.5 ?

40. One of the simplest of double ver-
niers is found on the Surveyor's Transit,
by W. and L. E. Gurley. The scale
space is h° and each half of the vernier
covers exactly 29 scale spaces. The least
count is 3V of 30 or 1'. It is a direct vernier,
and as represented in Fig. 5, divisions 7
and 23, are coincident. The reading with
the outer scale numbers is 177^-° + 23'
= 177° 53'; with the inner scale numbers

COMPLEX SUBSCALES.

42. A complex sub scale is one which is
neither simple nor vernier.

43. Equations (1), (2), (3), (4), (5), are
applicable to complex subscales, provided
q>l, § 9, q'>l, § 22, and either r>l
or r>l, §9, §22, §27.

If r and ?•' are known the elements
may be determined as in § 11. For a

Fig.6

2° 7'. Care must be taken to read the
half of the vernier which is forward ar-
ranged, ? 29.

The corresponding retrograde vernier
would cover 2 x 31 instead of 2 x 29
scale spaces.

41. A double folded vernier correspond-
ing in use to that in Fig. 5, is repre-
sented in Fig. 6. It is, however, retro-
grade. The entire vernier of 30 spaces
covers 31 scale spaces of £° each. The

given scale and subscale q and q' may
be found by direct observation, § 15.

If r and r are both unknown, the
other elements may be readily found,
§ 11, § 15. Equations (4) and (5) express
the same relation and furnish a means of
determining r and r which are of use
in numbering the subscale, § 46. (5) is
the simpler form to use, and must, from
its deduction, be capable of solution for
each subscale. This does not further

310

VAN NOSTRAND'S ENGINEERING MAGAZINE.

limit the values of q and q',12 and in
each case one and but one set of integral
value for r and r' not exceeding * 3

12 To show that (5) is capable of solution
with integral values of both r and r', no
matter what mutually prime integers q and q'
may be.

If q=l or q'=l, the above statement is self-
evident.

If q>q'>l, divide q by q' and continue the
division until a remainder dx <q' is found. In
like manner divide q' by d± with a remainder
d2<q', dt by d2, &c, until dn= 1, which
must result (.Gr. CD.), since q and q are mutu-
ally prime. Denote byccac3, &c, the succes-
sive quotients, then

dt=q-q'c

dz=q'—d1c1. . ,

d3=d1—d2c2

&c.

dn—\—dn—%— dn— %cn.
l = dn—2—dn — i cn — \. .

.(1).
.(2).
.(3).

y (a).

,...{n).

in which all the letters represent positive in-
tegers.
In (n) group {a), replace cn—\ by k±

l=dn—2,k1—dn—i

then replace dn—\ by its value from (n— 1)
group (a), giving

1 = — &x eZn-a+^+A! cn_2)^n_2-

Let k2=l+k1 cn_2, and we have

— 1—kidn — 3 k2 dn — 2-

In like manner combine this equation with
(n—2) group (a), denoting the new coefficient
of dn— 3 by k3, &c, throughout group {a). The
results may be written

l=dn-2— kidn-i (1)

■l=k1dn-s—^dn—2-
■kod

3an— 3.

.(2)
•(3)

1 — k2dn — 4

&c.

(-iyi-2=kn_2q'-kn-i d1..{n-l)
(-l)n-i=kn_iq-knq' (n)

in which

kL=cn—i. k2 = l-\-k1cn—2. ks=k1-)-cn_3.

kn—i^=kn—'6Ji~knl—2^i- kn ~ kn — 2+^n

y (b).

&c.

_1C

We may then determine klt k2, &c, to kn,
which are all positive integers. Comparing (n)
group (b) with

±l=r'q— rq' (5).

we see that r=kn, r/=An_i, will satisfy it.

If q' > q > 1 an equation analogous to (n)
group (b) may in like manner be found, and a
set of positive integral values for r and r' in (5)
determined.

13 Let s, s' represent any known set of in-
tegral values for r and r' respectively in (5),
then

±-\=s'q—8q' (c).

i and %

respectively, can always be

found, when q and (/ are known. These

Adding nqq' to, and subtracting it from the
second number of (c) we have

±1 — (s'+nq')q— (s+nq)q/. . . {d).
±l=(8'—nq')q—(s—nq)q'. . . (e).
Tl=(nq'—s')q—(nq—s)q'. . . (/).

Comparing (d) (e) (f) with. (5) we see that

From any set s,s', of positive integral values
of r and r' in (5) other such sets may be formed
by adding nq and nq' to, or subtracting nq and
nq' from s and s' respectively, n being any in-
teger. Positive results belong (d) (e) to the
same (± ) form as s and &•', negative results with
their signs changed (/) to the opposite form.

This is the law of formation of all possible
integral roots of (5) ; for let I, t' be any other
set of such roots, then

±1=6'^— sq' (c).

±l=rq-tq' (g).

If both sets belong to the same form the signs
of the first members are alike, and

o=:(s'-t')q-(s-t)q'.
8 — t q

s'—t'-q'

in which since s, s', t f, q q' are integers, and

— is irreducible.
q'

s—t=nq (h).

s'—t'=nq' (k).

n being some integer.

If the two sets of roots belong to opposite
forms

o=(s'+f)qr-(s+t)q'.

and

8+t _q
s'+l'~q'

s+t=nq.

s'+t'=nq'.

..... (I).
(m).

in which n is some integer.

In both cases t and f may be formed from 8
and s/ respectively by the above law.

We are now ready to show that :

One and but one set of integral values for r

Q Q/ -

and r' in (5) not exceeding |- and ~ can always

be found.

From the above law, one set and but one in
each form of (5) can always be found not ex-
ceeding q and q' respectively. Let c, c' denote
the least set for the first form d, d' ', that for the
second form, then

l=c'q—cq' (n).

■c q—cq .
-l=d/q-dq/.

(Pi

also c+d<2q, and c'+d'<2q', which requires
(I), (m)

c+d-q (v).

c'+d'=q' (*)

SUBSCALES, INCLUDING VERNIERS.

Sll

are the least possible integral values of
r and r' in (5), and are the required
values jf 10. To find them, substitute for
r' [or r] in (5), 1, 2, 3, &0., in succession,
deduce each corresponding value of r [or
/] until an integral result is obtained.
The integral values of r and / so ob-
tained are the required values, if they

do not exceed ~ and ~ respectively ; if

'- -

either exceeds, subtract them from q and
tjf respectively, the remainders will then
be the values required.

If r and q [or r and q~] are given, r'q
may be found from (5), and r', q, will be
integral factors of the product. Each set
of such factors, satisfying the conditions

r= or <|, r'= or<^, q and q mutually

— _

prime, will give a subscale.

If r and q [or r' and q'~\ are given, the
values of r' and q' may be found in the
same manner as those of r and / when
g and q are given. The above conditions
must, in any case, be satisfied.

44. Reading. Let I, a, b, q, q', r, r\
be the subscale elements, as in § 9, x the
subscale reading for any complete sub-
scale. Conceive an auxiliary scale and
subscale formed by erasing on the scale
and subscale all lines of division except
on the scale, the division of reference
and those divisions separated from it by
/•'. 2r', &c, scale spaces ; and except on
the subscale, its o, ?*, 2r, &c, divisions.
Denote by a', b', the new scale and sub-
scale spaces respectively. a'=r'a. b ' —
rb ; whence (5).

±l=a'-b'.
If c<d, (v) gives c<~, which in (n) gives

q' 1
c'<£--i — ; but c' is an integer, and <7>1 (for
2 q

q'
complex subscales), so thatc'=or<£. c and

c' do not exceed |- and u|- respectively, while

This Bhows the new subscale to be a
vernier, § 27, whose least count is /. It is
direct or retrograde with the given sub-
scale. The subscale reading and vernier
reading in any position measure the Bame
distance, since the division of reference
and subscale zero are in common.

Hence, § 28,

x=?il (10).

x=a — nl=(q — n)l. . (11).

Q .

If c=dt (v) gives c=~, and from (n), c' =

% + ->%> which in (s) gives d'>|, with d=|.

If c>d, (v) gives d<% and (p), d'<%---
2 2 q

In each case one set of such values, and but

one, can be found.

according as the vernier is forward or
backward arranged, n denoting the order
of the coincident vernier division. Since
ql=a,q vernier spaces are sufficient. The
/ith vernier division is the rnhh subscale
division. If r?i<Cq, the coincident divi-
sion is on the complete subscale ; if rn > q,
the subscale divisions m—q, rn—2q, &c,
are also coincident, § 10, and some division
of the complete subscale also coincides.
Let this division be numbered n. It will
then be only necessary to multiply n by
I for the subscale reading in equation
(10). This, § 20, corresponds to forward
arrangement of the subscale. The dis-
tance is expressed, § 28, to the nearest
unit with I as the unit of measure.

45. The conditions for forward and
backward arrangement of the subscale,
are the same as for the auxiliary vernier.
A change in the direction of the number-
ing, § 29, reverses the arrangement.

46. The law of numbering imposed,
§ 44, on complex subscales requires that
the subscale division coincident in the
same position as the nth. division of the
auxiliary vernier, shall be numbered ?i,
whatever value n may have from o to q.
Every given vernier division has its cor-
responding subscale division separated
from it by sq subscale spaces (s being an

. integer). If n is not o or q, there can be
. but one corresponding division on the
I complete subscale. Apply the complete
subscale, whose length is qb, successively
r times to the vernier whose length is
q X rb. At each application the subscale is
moved q spaces. On the (s-f-l)th appli-
cation the corrresponding subscale divi-
sion will be superimposed on the given
vernier division. All the numbers may
be located in this way. Each applica-
tion locates several numbers on the sub-
scale.

312

van nostrand's engineering magazine.

Let^=&t+-^.

&c, to

= &r + 0 = <£.

1st. Numbers 0, 1, 2, &c, to k1 are lo-
cated on the o, r, 2r, &c, to &,?•
subscale divisions.

2d. (^ + 1), (^+2), &c, to *?,=*, + (*,
—A;,) on the (r— #,), (2r— #,), &c,
to [(&,— A;,)r— g,] divisions.
&c, &c, &c.

rth, Ajr-i + 1, &r_i + 2, &c, to &r = <? on
the (r — qr-i), 2r — ^r— 1> &c, to #
divisions.

47. The position of the subscale zero
may be intermediate, as may be shown
by replacing the word vernier by sub-
scale in § 30. The non-consecutive num-
bering 14 renders such an arrangement
more confining than on a vernier.

48. A rule for measurement with scale
and complex subscale forward arranged,
may be had from that of § 31 by replacing
the word k' vernier " by " subscale." The
same change also renders § 32 and § 33
applicable to the use jaf complex sub-
scales.

49. If I is less than the width of the
dividing lines, several subscale divisions
will be coincident at the same. They
correspond to consecutive divisions of
the auxiliary vernier § 44, but are separ-
ated by r subscale spaces or r' scale
spaces. They are in general non-con-
secutive subscale divisions, consecutively
numbered, and the middle one must be
taken as coincident, § 34.

The comparison to determine which
divisions are coincident is in general
more difficult than on a vernier; for,
being non-consecutive divisions, they are
not so readily grouped by the eye. If
r=l, r'>l, the coincident divisions are
consecutive on the subscale, and this dif-
ficulty disappears. But the complete
subscale covers (r'qzpl) scale spaces (5)
while the equivalent vernier would cover
only {q^fl) spaces (9). If r>l, r' = l,
the coincident divisions are consecutive
on the scale, and the difficulty also disap-
pears. The complete subscale then cov-

14 The subscale might be numbered con-
secutively, and its reading found when any
division coincides But the operation of find-
ing the reading is too complicated for con-
venient use.

ers (^-*— ) spaces and is more compact

than the equivalent vernier.

50. If the subscale is redundant or
complete, the division numbered n will
exist for all values of n (o to q), and
every distance less than a can be directly
measured by it. If the subscale is in-
complete, the division numbered n may
be beyond the limits of the subscale.
Such a subscale cannot measure directly
every distance less than a and is incon-
venient for use. It may, however, be

used, provided it contains ~ or more

spaces ; for the numbers are interchanged
on the two halves when the arrangement
is reversed, § 45. It must be capable of
use arranged either way.

51. Classification. — In all subscales,
the scale and subscale spaces must, note
5, § 7, be commensurable.

To determine whether or not a given
subscale is complex, apply the tests for
simple subscales, §§ 21, 22, and vernier,
§ 36 ; if it is neither of these, it must be
complex. When r and / have been de-
termined, the condition that one of them
shall be greater than unity is more con-
venient. Whether the subscale is redun-
dant, complete, or incomplete, may be
decided as in § 15. The condition for
direct subscales is rb<r'a, or rq'<r'q:
for retrograde subscales rb > r'a, or rq' >
r'q, § 12. Either form may be used.

Subscales may, like verniers, be further
classified, § 37, as single and double. A
double folded subscale would, however,
be too complicated for convenient use,
unless r=l.

52. Illustration. — Required a complete
complex subscale to go with a main scale
divided to J- inch, which will enable one
to measure to -*4-n inch. There are but

two given quastities a—\, l^=T^i and
the problem, §§ 11, 43, is indeterminate.

From (1)

a OK

2=-=25.

Repeating (5).

±l=r'q— rq' (5).

we see that if different values are given
in succession to r', values of rq' will re-
sult, each of which, if composite, may be
factored, giving sets of values of r and q,
for each value of r' . b may be found (2)
from q' and I. Each such set of values

BUB80ALE8, INCLUDING VERNIKIIS.

313

will give a different required subscale, if

r = <^ and
A

§43.

In the most compact form, § 49, rl' = l,
which in this case gives rq =25? 1. Tak-
ing the upper sign, £ 42, for a direct sub-
scale, we may write /-=3, q* = S. The
corresponding subscale is represented in
Fig. 7. The subscale division 7 coincides,
and the final reading is 10.07 inches.

The number 24 affords several different
sets of factors, each of which could be
used, giving a required compact subscale ;
but care should be taken not to make the
subscale spaces too small for distinct

With a given least count, the best of
the convenient forms is determined by
the cost of making the instrument.

1st. If the least count is large enough
to be distinctly seen, it may be taken as
the subscale space of a simple subscale.
By taking the subscale as long as prac-
tical convenience will allow, the number
of divisions on the main scale may be re-
duced to a minimum, thereby giving a
less cost of manufacture than with any
other convenient form of subscale.

2d. If the least count is to be as small
as possible, consistent with convenience,
the scale space should be taken of a size

Fig. 7.

vision. This compact subscale may be
reduced to a vernier by simply dividing
each scale space into r equal parts. The
least count is also divided by r.

If the value of rq'' in (5) had been
prime we would have had either r = l or
g = l, reducing the compact subscale to
the vernier, § 27, or to the simple sub-
scale, § 22. The compact subscale is then
impossible; thus, if ^=30, and r'=l, rq'
= 29 or 31 (compare §§ 40, 41).

53. Relative advantages of simple,
vernier, and complex subscales. It is
essential to ease of reading, with any
scale and subscale, that the coincident
subscale division may be readily found ;
that the scale and subscale spaces shall
be large enough to be distinctly seen ;
that the divisions of both scales shall be
plainly numbered; and that the entire
subscale shall not be too long to be crit-
ically viewed at a single glance of the eye.
For convenience of record, it is further
desirable that the scale space shall be a
unit of expression, § 2, or some aliquot
part of one.

Facility of finding the coincident di-
visions requires that any division in its
vicinity, for at least one of the two scales,
shall the more nearly coincide the nearer
it is to the coincident division. This ex-
cludes from further consideration those
complex subscales in which both r > and
r'>l, §49.

Vol. XXVII— No. 4—22.

very near the limit of distant vision.
With a vernier, the scale space and vernier
space are nearly equal (8), and can be
practically seen with equal distinctness.
If the complete vernier is then made as
long as convenience will allow, it will
give a smaller least count than any other
convenient form of subscale. For the
subscale space, if different from the ver-
nier space considered, must be apprecia-
bly different unless both r>l and r'yl a
case already rejected; if appreciably less,
it is inconveniently small ; if appreciably
greater, either the entire subscale is in-
conveniently large or the least count must
be increased.

In all instruments for the accurate meas-
urement of angles, the cost increases
more rapidly with the radius of the meas-
uring arc, than with the number of divi-
sions on it, within the limit of distinct
vision. The size is further limited for
portable instruments by convenience of
transportation. In all such instruments it
is always desirable to have a minimum
least count along the arc, and no other
form of subscale can surpass the ver-
nier.

3d. If the least count is too small to be
taken as a subscale space, and not as small
as practical convenience will allow, the
vernier must be compared with those
complex subscales in which r=l or r'=l.
Of these the shortest for any given scale

314

VAN NOSTRAND'S ENGINEERING MAGAZINE.

and least count is the compact subscale
in which r>l r'=l. If such a subscale
can be found with its least space just large
enough to be distinctly seen, and its length
just within the limits of practical conven-
ience, it will surpass all other forms of
subscale. The equivalent vernier, r times
as long, is beyond the limits of convenient
length, while the equivalent subscale in
which r=l, r'>l is even longer than the
vernier. Thus in (Fig. 7) the compact

subscale is 2 inches long while the equiv-
alent vernier is 6 inches in length. To
constrct a vernier of convenient size would
require with the same scale a greater
least count ; and with the same least count
a greater number of scale divisions per
inch and a less absolute number of sub-
scale divisions, which if the scale were long
would increase the cost.

The advantage of the compact subscale
is limited to straight scales.

TRUSSES WITH SUPERFLUOUS MEMBERS.

By WM. CAIN, C.E.
- Written for Vak Nostband's Engineebing Magazine.

M. Maurice Levy in " La Statique
Graphique," note 2 (Paris, 1874), has pub-
lished a notable theorem concerning
trusses with superfluous members, or
those containing a greater number of
pieces than statics alone can define the
stresses in requiring a resort therefore to*
the theory of elasticity.

His conclusions are especially interest-
ing as bearing upon the economy of such
systems, and the writer therefore hopes
that a resume of his method may prove
useful to American engineers.

The aim has been to give the essential
features of Levy's demonstration, in all
their generality, though with certain mod-
ifications, in as simple and elementary a
manner as possible, without following in
all cases the method of the author, be-
sides illustrating with simple examples,
worked out in sufficient detail to enable
the reader to clearly appreciate the
methods involved.

The investigation of trestle piers will
likewise be entered into and proper stress
diagrams given for usual forms, without
superfluous bars, when acted on by the
wind and the weight of truss and train,
and certain objectionable features of
trusses and piers will also receive atten-
tion.

The figures of trusses may be clas-
sified into deformable, or those whose
angles can vary indefinitely, the lengths
of the sides remaining the same, and in-
deformable, or those whose angles are de-

termined when the length of the sides
are known.

The latter class may be divided into
two : those which cease to be indeforma-
ble when we suppress one of the sides,
called strictly indeformable figures, and
those containing more lines than are
strictly necessary to define the figure
when the lengths of the sides are given
in order, called figures with superfluous
lines.

A figure strictly indeformable contains
just enough sides, so that if the lengths
of these sides are given in order it may
be constructed.

Let us call m the number of the sides
and n the number of joints or apices of
the figure.

Then in order to construct it, draw any
line AB equal in length to one of the
sides (Figs. 1 and 2).

Fig.1

Fig. 2

Then describe two arcs of circles with
A and B as centers with radii equal to
AC and BC respectively. Their intersec-
tion will fix the position of joint C.

Similarly each joint or apex D or E is

TRUSSES WITH SUPERFLUOUS MEMBERS.

315

defined by the intersection of two sicU 8
and two only, the sides being taken in
the order assumed.

Therefore to each of the {n—2) joints
other than A and B correspond two sides
so that the total number of sides of the
figure, leaving out AB, is

2 (»-2) = 2w-4.

Hence the total number of sides includ
ing AB is,

m=2n-4 + l=2n-3.

If the figure contains k more lines than
the (2;t— 3) corresponding to a strictly in-
deformable figure, these k lines are super-
fluous (" surabondantes ") to define the
figure ; in fact their lengths depend en-
tirely upon the form and lengths of sides
of the first figure, so that there must exist
a geometrical relation between these
lengths.

Again it is evident that if we suppress
some of the sides of the first figure, that
the resulting figure is def ormable and can
be constructed in an infinite number of
ways.

From what precedes we see that we can
always recognize the three classes by the
following simple relations between the
number of sides (m) and the number of
apices (n).

Y ox def ormable figures . . m<Jln— 3

" strictly indef ormable fig-
ures m=2n— 3

" figures with superfluous

lines m> 2zi— 3

It must be carefully noted that these
relations suffice to distinguish the three
classes only when the parts into which a
figure may be divided, as well as the whole
figure, belongs to the same class ; other-
wise, it can easily happen that part of the
figure may have too few lines to strictly
define it and another part too many lines,
so that if the relation ra=2n— 3, for the
whole figure was fulfilled, it would seem
to indicate that it was strictly indeforma-
ble, whereas it is made up of figures be-
longing to the two other classes. The
relations above then must not only be
proved true for the whole figure, but for
any and every part into which the figure
may be supposed to be divided.

See Bow's " Economics of Construc-
tion " for a large variety of figures belong-
ing to the various classes mentioned.

§2.

It is a well-known fact that when statics
alone determines the stress in any bar, it
does so irrespective of the section of that
bar and consequently of its change of
length after stress.

Therefore in a frame in which the
stresses of the bars have been determined
by statics alone, we can vary the sections
of the bars, and consequently their alter-
ation in length under stress, indefinitely,
provided rupture does not occur, without
the stresses being altered in the least.

Consequently each bar must be free to al-
ter its length irrespective of the changes in
lengths of the other bars in order that sta-
tics alone can define the stresses, for these
stresses, once found by statics, remain
unalterable, whilst the changes in length
under stress vary with the sections, which
we can choose at pleasure.

This necessary condition requires that
the figure considered may be strictly geo-
metrically determined when we know
the lengths of the sides in order, and
that it does not contain any superfluous
lines, whose alterations of length are de-
pendent entirely upon the alterations in
length of the other sides. A system of
lines, such as we are considering, can be
constructed after strain exactly in the
manner shown for (Figs. 1 and 2), taking
the intersection of the new sides in order
to fix the positions of the various apices.

We can proceed in another way to show
that this requirement is not only neces-
sary but sufficient. Thus, consider a frame
subjected to external forces at the joints
in equilibrium. At each of the n joints
we can write two equations, representing
that the sum of the horizontal as well as
of the vertical components of the forces
there, including the stresses of the bars,
are zero. This gives 2n equations, but as
there are three necessary equations be-
tween the equilibrated external forces, in-
dicating that the sum of their horizontal
components is zero, the sum of their ver-
tical components is zero and their result-
ant moment about any point is zero, these
2n equations reduce to (2n — 3) indepen-
dent equations.

Now this is just the number of sides
(2n— 3) for a " strictly indef ormable "
figure, so that there are just as many
equations as stresses to determine, and
such figures, therefore, can be statically

316

VAN NOSTRAND'S ENGINEERING MAGAZINE.

determined. If there are more lines than
the (2w— 3), there are too few equations
by the excess, and the figure cannot be
statically determined.

For a def ormable figure there are more
equations than necessary and the equi-
librium is impossible unless the figure is
given such a form that the external forces
hold it in equilibrium.

We can state, therefore, the following
theorem :

Theorem I. — In order that statics can
furnish the stresses in a system of bars,
it is necessary and it suffices that the geo-
metric figure formed by the axis of these
bars may be such that ice can construct it,
by giving in order the lengths of all the
sides.

If the figure contains k superfluous
lines, statics will furnish k equations too
few to define the stresses in the bars; and
inversely, if statics gives k equations too
few to define the stresses we are certain
that the figure contains k superfluous
lines.

Levy establishes this theorem very sim-
ply by the consideration of the principle
of mutual velocities, wliich principle ena-
bles statics alone to determine the stresses
whenever the figure is such that we can
give to any one bar a small virtual elonga-
tion without changing the lengths of the
other bars. We have seen above, that
this condition is fulfilled when the figure
has no superfluous lines.

§ 3.

This principle applies not only to free
systems, but likewise to trusses, some of
whose apices are subjected to certain con-
ditions, provided these conditions affect
only the position of the truss in space
without influencing its form, so that each
bar remains free to change length inde-
pendent of the other bar. In this case,
for figures in a plane, statics furnishes
the reactions at the supports, so that the
figure can be considered as free and sub-
jected to the original forces to which are
added the reactions of the supports. If
this condition is not fulfilled, as for a truss
continuous over several supports or for
trusses fixed in direction, as well as posi-
tion at certain points, as the braced arch
fixed at the ends, etc., statics will furnish
too few equations to determine the reac-
tions at the supports by the number of

extra conditions over those specified
above.

In fact, statics furnishes three equa-
tions to determine the reaction at the
supports, viz., (1) that the sum of the
vertical components of the exterior forces,
including the reactions equals zero ; (2)
that the sum of their horizontal compo-
nents equals zero, and (3) that the sum of
the moments of these forces about any
point in the plane of the forces equals
zero.

So that if a truss is fixed at one point,
which involves two conditions (namely
the two co-ordinates of the point), and
free to slide at another point along some
surface, curved or plane, which entails
one condition or ordinate, in all three
conditions, then statics will furnish as
many equations as there are conditions,
so that the reactions may be found and
the figure be regarded as free.

But if we suppose the second point
fixed, as well as the first, this will entail
four conditions ; so that statics will fur-
nish one equation too little to determine
the reactions. If three points are fixed,
Statics will furnish three equations too
little, and so on.

In the case of the continuous girder,
one joint is fixed at one support and the
truss rests upon rollers at the other sup-
ports, so that statics furnishes too few
equations by the number of intermediate
supports.

In any case we can readily recognize
whether the truss has more sides than is
strictly necessary to build up the figure,
knowing the length of the sides, consid-
ering the conditions to which it is sub-
jected. If it has, then, by the theorem
just enunciated, statics alone cannot as-
certain the stresses.

In all cases, therefore, whether of
trusses with superfluous bars or of trusses
having more conditions to fulfil than are
strictly necessary to define the form,
knowing the length of the sides, statics
furnishes too few equations by the num-
ber of the superfluous bars or of the ex-
tra conditions.

We must then resort to the theory of
elasticity to furnish the extra equations
needed, which may always be found, for
whether we consider a truss with h super-
fluous bars or one subjected to such con-
ditions that its form can be fully defined
by leaving out k bars, there are always,

TRU88ES WITH SUPERFLUOUS MEMBERS.

317

necessarily, k geometrical relations be-
tween the lengths of the bars, and tin
fore k equations between their elastic
changes of length, which k equations
added to the m — k equations furnished by
statics give as many equations as the
number of the bars, so that the stresses
in the bars can be fully determined.

We have seen that for figures with no
superfluous lines or conditions, that the
strains are independent of the sections of
the bars and of the consequent elonga-
tions or compressions of the bars. If
more bars are added than strictly neces-
sary to define the figure, considering the
conditions, the changes of length result-
ing from stress in all the bars depends
entirely upon the geometrical relations of
the sides, and the stresses in the bars de-
pend upon these alterations in length,
having assumed their sections and moduli
of elasticity.

This is a marked difference in the two
classes of trusses and must be carefully
borne in mind in what follows.

Definition.— Where a truss is sub-
jected to such conditions, that its form
may be fully defined by leaving out k'
bars, these k bars are superfluous, in
fact, to define the form, and we shall ex-
tend the definition of § 1 and class such
trusses as belonging to systems with k
superfluous lines.

General method for -finding the stresses
in the bars of a truss when statics leaves
the problem intermediate.

Consider a truss with k superfluous
bars, or one subjected to so many condi-
tions that the figure is strictly geomet-
rically defined when k bars are omitted,
so that it really has k superfluous bars,
as just defined.

First write the {m—k) relations fur-
nished by statics. Now there exists k
geometrical relations between the
lengths of the bars, giving therefore the
lengths of k of the bars from the knowl-
edge of the lengths of (m—k) bars. Call

#,? #2i a3, . . . ,

the lengths of the m bars in the natural
unstrained state.

Under the influence of the forces ap-

plied at the joints of the truss, these bars
take the elongations

«,» «tJ «3' • ' • * '

If any of the bars are compressed the
corresponding a will be regarded as
minus.

Since we have k geometrical relations
between the lengths, let

F(a„ a„ a„

,)=* . . . (1).

be one of them.

When the bars take the increments of
length, this relation becomes

% + «„ «, + «*, «3-fa3, . . . ,) = 0 . (2).

If we call f the stress in a bar, w=
section, e= coefficient of elasticity, a =
original length of bar and a its increase
in length from the stress /, then we have,
from the fundamental equation of the
theory of elasticity,

af_
ew

. . . (3).

On subtracting (1) from (2), neglect-
ing differences of a higher order than
the first, which may be permitted in
view of the limit of approximation per-
mitted in the theory of elasticity, and
substituting the value of a from (3) for
each bar, we have one of the k equations
sought.

Similarly the whole of these equations
may be found.

These k equations thus obtained,
joined to the (m—k) equations furn-
ished by^ statics, gives m equations,
which are sufficient to determine the
stresses in the m bars.

It may be remarked that it would be
erroneous to assume the stresses of k of
the bars, so that with the aid of the
(?n—k) equations of statics, the stresses
of the others could be determined, for

from (3) the stress in any bar, f=eio-

depends on the modulus of elasticity,
the section and elastic elongation for
unit of length, so that without consider-
ing the deformation of the whole truss
or the relative elongations of the bars,
the stresses cannot be correctly found,
since each elongation depends upon cer-
tain other elongations.

318

VAN NOSTRAND'S ENGINEERING MAGAZINE.

We may express the method to be fol-
lowed (see preceding page), in another
manner.

Thus write Eq. (1)

F(«l5 a2, «3, . . . )=F=o,

then by the theory of homogeneous
functions

dF d¥

dan

On substituting the values of al9 a2,
. . . from (3), we have one of the k rela-
tions sought

-T-ai-LL- + j—a*"jLs-+ ' • • ~° ' (4)-
da1 elw1 daM1 ezw2

Similarly we find the remaining rela-
tions.

§'5.

As an example illustrating the method
to be followed, consider in Fig. 3, a sys-
tem consisting of four bars, proceeding

Figv3

from four fixed points c0, c,, c2, c,, in a
vertical wall, to a common point A, where
a weight W is applied.

The distance c0 c1—e1ci=cqc.=b ; the
lengths of the bars respectively are, «0,
a,, a2, as; their angles with the hori-
zontal fi0 = o, /?,, /32, /?s; and their stresses
/;, /;, /;, and /; respectively.

As there is only one joint A, statics
can furnish but two equations,

/1sin/?1+/,sin/?ll+/,sm/?-W=o . . (5\

/;+/1cos/?1+/1cos/?,+/;cob/?3=o . . (6).

These two equations by themselves
can only determine the stresses when
the number of the bars is two.

It is seen that two of the bars alone
fix the position of the point A, so that
there exists a necessary relation between
the lengths of the remaining bars and of
the first two.

Now between the lengths al9 a2, a3, we
have the relation,

. < + a82=2aaa + 2&2,

and calling the elongations under strain
of the bars whose lengths are a0, al9 a2,
a% respectively, ao, al9 a2, a3 respectively,
we have after the elastic deformation,

(ai + a1)2 + (a3 + a3)2 = 2K + a2)2 + 252;

subtracting the former equation from
the latter, and neglecting the squares of
the elongations, we have,

Or introducing the values furnished by
eq. (3), we obtain, as one of the required
relations,

e.io.

+ a.

:2a,'

enw„

(7).

The same result can be obtained by
use of eq. (4).

In a similar manner, we should find,

enwr

+ «0

ZL— 2a2-*£-

ejw„

e,w.

(8).

These last two equations added to the
first two furnished by statics, give four
equations to determine the stresses in
the four bars.

As before observed, these stresses de-
pend upon the sections assumed or given.
Thus with a given set of bars, whose sec-
tions are w0, iol9 wi9 ws, and moduli of
elasticity e0, el9 e2, e3, respectively, we
readily find from the 4 equations, the
stresses fo9 fl9 /*2, f%9 by successive elimi-
nation and substitution. These stresses
are thus found as numerical quanities,
where tension is plus, and compression
minus, from whence the stress per unit,

- for each bar can be determined.

By varying the sections we thereby
vary the value for the stresses, which can
thus be altered indefinitely, and in fact
changed from tension to compression or
the reverse in some cases. We thereby
see the great influence of each section
on all the stresses for systems not stati-
cally determined.

TRUSSES WITH SUPERFLUOUS Ml.MBERS.

319

If the object is not simply to know
the stresses in a given frame of the form
considered, but to design the frame, so

that the unit stress - shall be a certain

amount (which may be different for each
bar), we must substitute the values of

- .'- for each bar in eqs. (7) and (8).
e to

The result will show the geometrical
relation that must exist between the
lengths of the bars, in order that the
hypothesis may be realized.

In case the relation does not show or
lead to an absurdity, when the proper
signs have been given to the stresses,
always agreeable to the laws of statics,
the system may be constituted with the
kind of stress and the unit stress for
each bar as assumed.

This part of the subject will be more
fully treated in discussing systems of
equal resistance.

As a second example take the figure
formed by a rectangle and its two diag-
onals, not connected where they cross, and
capable of taking both tension and com-
pression.

Here we have ?i=4: joints and ?n — 6
bars, so that ?n>2?i — 3 and the figure
has one superfluous line.

Suppose forces applied at the four
joints A,B,C,D, to hold the figure in
equilibrium.

At each apex, statics fiurnishes 2 equa-
tions between the external forces and
the stresses of the bars, in all 8 equa-
tions, but as the four forces satisfy 3
equations of equilibrium, these 8 reduce
to 5 independent equations, or one equa-
tion too little to determine the stresses
in the 6 bars.

To find the (>th equation, we resort
to the geometrical relation between the
lengths of the sides, in conjunction with
eq. (3).

Thus call <( = ((' the original or un-
strained length of AB and CD, a and a
their elastic elongations; b = b', the
primitive length of AC and BD, /Sand />'
their elongations; c=c' = \/a'i + b~, the
length of the diagonals and y and yf,
their elongations, as marked on the
figure.

We have

ca=aa + 52

After deformation, this relation can be
expressed in four different ways, accord-
ing to the sides considered. Subtract
the first equation from each of the four
in turn, neglecting the squares of the
elongations, add the results and divide
by 4 ; we obtain,

c(y + /') = «(« +«') + &(/* + /?') . . . (9).

By aid of (3), this eq. is transformed
to another, which in connection with the
5 eqs. given by statics, suffices to de-
termine the stresses in the 6 bars.

If the sections of a frame of this kind
are given, we find the stresses (plus or
minus) from the previous equations

each

from whence the unit strain - for

bar is ascertained.

Where a figure of this kind consti-
tutes one of the panels of a Pratt truss,
the bars CD and AD, say are in tension,
and AB, AC and BD compression. Let
us ascertain whether CB is stretched or
compressed.

Eq. (9), now takes the form

c(y + r') = a(a' + a)-b(P + P'). . . (10).

Let us suppose a common modulus of
elasticity for all the bars and denote the
stresses in the bars AB, CD, AC, and BD
by /,» /■»/■> /*4» respectively, and the cor-
responding sections by w^, i0a, ic3, wj
then by the use of eq. (3), (10), becomes

' e \w^ wj e \ w3 wj

. . , (ii).

A quantity essentially negative ; for as
there is generally but a small difference
in the stresses of the chords AB and CD,

320

VAN NOSTEAND'S ENGINEEEING MAGAZINE.

the quantity (a difference) inside the first
is genrally small compared with
the quantity (a sum) inside the sec-
ond j ] ; consequently (y + y) must be
negative, but as y was assumed positive,
it follows that y must be negative and
numerically greater than yr\ so that CB
must be shortened when AD is length-
ened as assumed. Therefore, if the bar
CB is of such a small section, that it can
receive no appreciable compression, it
must be considered as out of action al-
together, so that the system becomes
statically determined.

In the Howe truss the diagonals can
only receive compression, as their ends
are simply butted against angle blocks,
and we can prove for this truss in a simi-
lar manner that when one diagonal acts
the other does not act, so that this sys-

the stresses in these bars together with
the weight P taking the place of the
external forces previously supposed to
act at the four joints of the rectangle.

To find the stresses in the 6 remain-
ing bars, it is simpler, as Levy re-
marks, in place of writing the 2?i equa-
tions for the 4 joints, as above, to use
the method of moments, in conjunction
with that of sections, so that we write
at once the 5 equations furnished by
statics.

Call the stressses in bars AB, CD,
AC, BD, CB, and AD, /,,/,,/,,/,,/;,/;,
respectively, and their corresponding
sections, w^ ws, to3, ia4, wb, w6. We shall
regard the modulus of elasticity the
same for all the bars, and write the
equations as if all the bars were in
tension, since the plus or minus sign

tern can likewise be statically deter-
mined.

It is well to call attention to these im-
portant distinctions, for they do not
seem to have occurred to Levy, who
classes all trusses having crossed diag-
onals with figures " a lignes surabon-
dantes."

Thus in the next figure, representing
the ordinary queen post truss, we shall
suppose the diagonals capable of taking
either compression or tension at pleasure
(which is not the case in American prac-
tice as just stated), so that the figure has
one superfluous line, and statics will fur-
nish one equation too little to determine
the stresses.

With one weight P, applied at the
joint A, the reactions Q, and Q2 at E and
F are found by the law of the lever and
the stresses in the four extreme bars
EA, EC, BF, and FD, follow from the
ordinary laws of statics. We have thus

found finally for any stress, from the
resulting equations, will show whether
the bar is in tension or compression.

Suppose a section xy to cut the four
bars shown and that the right part of
the figure is in equilibrium under the
action of the stresses in the four cut
bars and of the reaction Q2.

Taking moments about the point B
we have

(/;-h/;cos0)6-Q2rf=0

(12).

Calling cp the angle ADC and d the
distance BF.

Similarly, taking moments about D,

(/t+Z.cos^a + Q.fco . . . (13).

Next balance the vertical components
of the stresses at the section xy with
the reaction Q2,

(/i-/,0)sin^=Q1

(14).

TRU88E8 WITH srPKKFLUOUS MEMBERS.

321

Now express thai the vertical com-
ponents of the stresses meeting :it the
point Bare in equilibrium,

ncp+f=o . . . (15).

The analogous projection for the point
A gives,

-•ncp+/ = -F . . . (17).

The^e arc the five equations, involv-
ing the stresses of the six bars, fur-
nished by star

The sixth equation needed is ob-
tained, as was Eq.(ll), only regarding all
the alterations in length as positive or
elongations.

+p(£+£\ . . (17).

By elimination between these six equa-
tions, having given the sections wx, ioif
. . . , we find the stresses (plus for ten-
sion, minus for compression) in the six
bars, and subsequently the unit stress
f
— for each of them.

This truss is usually designed, wTith
such small sections for the diagonals, that
the stresses in the other members of the
rectangle are such as statics alone would
give provided one diagonal w7as left out,
i.e.. the top chord and posts in compres-
sion, the bottom member in tension. If
we suppose one of the diagonals to take
tension, the other, as we have seen, will
take compression, so that Eq. (9), can be
written for the most usual case,

c(X'-y = a)(a'-a)-b(/i + /f)

(18).

We may anticipate the next section, for
this case, by asserting that this truss, de-
formed in the manner assumed, can never
be made one of equal resistance; for in
such forms, we shall find further on, that
the changes in length per unit of length
must be the same for each bar.
. Tins amounts in this figure to making
Y=y', a = a', and fi=fi', which reduces
Eq. (18) to

o=o—2flb,

which is absurd.

In fact it may be shown (see Levy's
note) that on any supposition, agreeable
to the laws of statics, of the signs of the

stresses in the six bars considered, the
system cannot be made one of equal re-
sistance.

Where a number of rectangles with two

diagonals each, like Fig. (>, are placed side

by side, the diagonals being capable of

taking tension and compression, we have
a form of truss with as many superfluous
lines as rectangles.

The preceding methods can be applied
to each rectangle in turn, so that the
stresses in all the bars can be found. It
is evident how much we gain in simplicity
by constructing the truss, so that the
diagonals can only take one kind of strain,
and since the former systems cannot be
made of equal resistance, for any given
loading, we should expect no economy in
their use, as indeed will be demonstrated
later for all systems with superfluous bars
in the exceptional case where they can be
constituted systems of equal resistance.

§ 6.

SYSTEMS OF EQUAL RESISTANCE.

In designing certain frameworks, we
generally require that all the bars in ten-
sion shall be subjected to a certain nnit
stress and that all bars in compression
shall sustain a certain other nnit stress.

If the modulus of elasticity is not the
same for the bars compressed as for those
in tension, we may require that the stress

f
per unit - multiplied by the reciprocal of

the modulus -, may be certain amounts

for the bars in tension and in compression ;

so that for all bars in tension,

f
— —elongation per unit of le?igh=c'

(19).

and for all bars compressed,
ew

shortening per unit oflength=.c"

(20).

c' and c" being certain numerical con-
stants.

We regard here, as formerly, compres-
sions as minus tensions.

f
The unit stress, - =ce, varies now with

w
the modulus of elasticity.

Such systems will be called systems of
equal resistance.

322

van nostkand's engineeking magazine.

Now if we wish to ascertain the condi"
tions that a system of bars should satisfy
in order that they may be constituted a
system of equal resistance, for the load-
ing considered, we must substitute in Eq.
(4), the values (19) for bars in tension,
and the values (20) for bars compressed.

Let us designate by the subscript %
that the corresponding bars are in tension
and by the subscript^', that the bars con-
sidered are in compression ; then on sub-
stituting the values (19) and (20) in the
k equations (4), fhe k equations that re-
sult can be put under the following form:

\Al\Jjr,

(21),

the first 2 referring to all the bars ex-
tended, the second to all the bars com-
pressed.

Equation (21) represents one of the h
equations of conditions.

Now we do not know in advance which
bars are compressed and which extended ;
in fact the laws of statics will admit of a
great many combinations, and each of
these combinations will give a particular
system of Eq. (21) ; but in order that the
system of equal resistance may be possi-
ble, it is necessary that on£ at least of
these combinations may be satisfied and
that the signs of the stresses resulting
must be as assumed in Eq. (21) .

In fact we cannot, even when the equa-
tions of statics are satisfied, arbitrarily
assume the signs of the stresses of but
(m— k) of the bars, for the k equations
(21) determine themselves the signs of the
other stresses.

The most natural combination, and the
one which the constructions would gen-
erally justify is that in which the signs of
the stresses of the (m—k) bars are such
as statics would give if the h superfluous
bars were removed.

If we multiply equations (19) and (20)
by the lengths, a' and a" of the corre-
sponding bars, we have for the bars in ten-
sion, the total elongation,

a'=c'«'=a constant .... (22).

and for the bars in compression, the total
shortening,

a"=c"a" — & constant .... (23).

It is therefore a distinctive characteris-
tic of systems of equal resistance, that
the total alterations of length remains the

same for each bar, however the forces or
sections may be varied.

If we vary the section of one of the
bars and its consequent stress f=cew, we
therefore change the stresses and conse-
quently the sections of all the other bars ;
but if the signs of the stresses remain
the same, the elongations per unit of
length and also the total elongations of
the bars are exactly the same as before, as
follows from the preceding equations,
and every supposition as to the sections
of the bars embraces this hypothesis.

Therefore we may vary the sections in-
definitely and consequently the stresses,
provided the signs of the stresses result-
ing are such as assumed, agreeable to the
laws of statics, and the system will still
remain one of equal resistance.

We can thus announce the following
theorem :

Theorem II. — In order that a system
toith k superfluous bars may be constituted
one of equal resistance, we require :

1st, that the k geometrical relations, ex-
pressing that the alterations in length per
unit of length, may be constant for all
bars in tension and for all bars in com-
pression may be satisfied, and 2d, that
the resulting signs of the stresses must
be agreeable to the laws of statics.

If these conditions are satisfied for cer-
tain assumed sections, the system will not
cease to be of equal resistance, however we
vary the sections, provided the resulting
signs of the stresses are as first assumed;
i. e., if a system co?itaining superfluous
lines can be constituted a sgstem of equal
resistance in one way, it can in an
infinite number of ways.

As it is a fundamental property of sys-
tems of equal resistance that the changes
of length from strain, per unit of length
is constant for bars in tension and for
those in compression, we have a simple
test to apply to any figure to see if it can
be made a system of equal resistance.
Thus, having assumed the bars elongated
or compressed, according to the laws of
statics, we have only to ascertain if, after
deformation, the changes of length of all
the bars in tension are the same per unit
of length, and that the changes of length
of all the bars compressed are the same
per unit of length.

TRUSSES Willi SUPERFLUOUS MKMBl

323

If this geometrical relation is fulfilled,
then the system may be constituted one
of equal resistance, otherwise it cannot,
at least for the kind of strains assumed.

One ease maybe specialty mentioned,
where the bars are all supposed to bo
lengthened or all compressed, the same
amounts per unit of length. The de-
formed figure is of course similar to the
original figure, so that the first condition
is realized, but the second is not, for such
modes of deformation are not generally
agreeable to the laws of statics. It will
generally be found that most trusses with
superfluous lines cannot be made of equal
resistance. Thus we have seen in the
case of the rectangle with two diagonals,
that it cannot be so constituted, for the
same unit stress throughout.

Let us examine Fig. 3 in this regard.
First let us discard the upper bar, so that
we have a figure formed of three bars,

can draw any stress diagram that will give
the lower bar compression and the Uppei
bars tension and proportion the sections
for the same unit stress as assumed.

If the two lower bars are suppo
compressed, we have as the necessary
condition,

which reduces to b= —

, a negative so-

lution indicating an impossibility.

Let us next test the original figures
with four bars, and assume the three up-
per bars to take tension. Considering
the relation between the three upper
bars, a1a + a32=2a22, we deduce 2d*=0, an
absurdity, as then the frame reduces to
one line. If we assume the two lowest
members compressive, the others tensile,
eq. (8) in this case gives the absurdity

— v

whose lengths are b0, bt and £2. Here we
have one superfluous bar. Let us assume
that the lower bar takes compression
and the other two tension, which is agree-
able to the laws of statics.

If the system is to be made one of equal
resistance for tension and compression,

f
the elongations per unit — must be the

same for all three bars, so that Eq. (8) re-
duces to

But as cC = a0- + 4:b-y and a*=a9* + b*>
this reduces to

b=a0;

so that if we construct the system so that
this condition is satisfied, the bars will
receive the same unit stress, no matter
what sections are assumed, the stresses
being varied to suit, provided the char-
acter of the stresses does not change.
In fact, for this case, when b=a0 we

found above, a0= —3b, and eq. (7) the
other absurdity 2a0a = o.

Similarly, we could proceed on any
hypothesis, agreeable to the laws of stat-
ics or a stress diagram. We see that for
reasonable assumptions the system with
four bars cannot be constituted of equal
resistance, but that the system with three
bars may be so constituted (by making
b=a0) in an infinite number of man-
ners.

The same conclusions hold if the

frame is turned upside down, only the

i corresponding stresses change character.

Let us next examine the continuous
girder of two equal spans, Fig. 6, and
see if it can be constituted a system of
equal resistance. In this figure, the in-
clined members are all equal, and the
sides AB, BC and FD are equal. We
have here one superfluous line, say FD,
since the joints F and D are fully ascer-
tained when the sides of the two tri-
angles ABF and BDC are given.

324

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

Under the influence of two equal ver-
tical loads applied at F and D, the truss
will be deformed to some other, shown
by the dotted lines. If the superfluous
bar FD was removed, both inclined mem-
bers would take compression, and the
members AB and BC would be extended,
so that we shall make this first supposi-
tion for the full figure.

If we suppose the diagonals to be com-
pressed an equal amount, and the sides
AB and BC to be extended an equal
amount in a horizontal direction (which
involves the sliding on rollers say at A
and C), then fd is horizontal and ~Bfdc
and ~Bafd are parallelograms, since two
opposite sides are equal, and the other
two sides are parallel, so that fd=l$a
=Bc, and the elongation of FD is the
same as that of AB or BC. Now since
these sides are equal in length, this is a
necessary condition in order that the
truss can be constituted a system of
equal resistance, and as it is fulfilled we
conclude that for the character of- the
stresses assumed, this truss may be made
a system of equal resistance. The same
holds when the truss is inverted, only
the pieces formerly elongated are now
compressed and the reverse.

If the truss was fixed at A, B and C,
an equal compression of the inclined
members would simply lower the apices
F and D vertically, so that F D could re-
ceive no elongation, and the system can-
not be constituted one of equal resist-
ance, except when the bars AB, BC and
FD are removed, when of course there
would be no superfluous lines.

If we suppose AF and CD compressed
and BF and BD elongated, it can easily
be shown that the system cannot be made
of equal resistance.

In fact if A and C are on rollers, it is
evident that fd will be longer than
Bc=Ba, since for the same height the
triangle B/# has one inclined side equal
to one side of the triangles Bet/* or T$dc,
and the other side longer, so that the
base fd is longer than Ba or Be.

This holds for a stronger reason if the
joints A, B and C are all three immovable.

We have thus seen that for one com-
bination of stresses, the system may be
made of equal resistance. Further, on,
we shall resume this example again, and
show that this combination is agreeable
to the laws of statics.

For bridge trusses in especial, where
rolling loads are concerned, constructors
generally vary the unit stresses for the
different members, so that there may be
several values for c' and c", eqs. (19) and
(*20), to satisfy. Jn such cases to ascer-
tain if a certain truss can be constituted
one of the varying resistances assumed,
we suppose certain pieces compressed
and others extended, agreeable to the
laws of statics (and the simplest supposi-
tion would be that given by statics alone
when the superfluous bars are omitted),
and then ascertain if the alterations in
length per unit of length, after elastic
deformation are as assumed, regarding
the geometrical connection of the parts.

§ 8.

When there are no superfluous bars,
the frame can always be constituted one
of equal resistance if desired, for statics
furnishes at once the stresses in all the
bars, irrespective of their sections, so
that the last can be chosen at pleasure to
suit the unit strains.

We have seen above that systems with
superfluous lines cannot in general be
constituted systems of equal resistance, but
that when this happens in one way, they
can be so constituted in an infinite num-
ber of ways by suitably varying the sec-
tions.

It is therefore pertinent to inquire, if
such systsms with superfluous lines are not
more economical than statically deter-
mined systems ? If so, there is some jus-
tification in using them, otherwise not,
even when they involve the same amount
of material ; for as misfits and other dis-
turbing influences must occur in practice,
the resulting stresses, for systems with
superfluous lines will be different from
the assumed, some being greater, some
less ; so that the limit of security is not
as great as assumed ; whereas in statical-
ly determined systems, the unavoidable
misfits do not affect the strains, since
each bar ' is free to change length, irre-
spective of the other bars, and the limit
of security is the same as was assumed.

As preliminary to the inquiry before
us, we shall establish the following lem-
ma:

Lemma. — If a figure with k superflu-
ous lines is such that we can, in one man-
ner, and consequently in an infinite num-
ber of manners, dispose the sections of

TRUSSES WITH SUl^ERFLUOUS MEMHKKS.

825

its bars, so that it forms a system of
equal resistance for the loading assumed,
ice can always, by suppressing some of the
bars, form a system without superfluous
lines, which subjected to the same load-
ing, experiences the same elastic deforma-
tions as the primitive system, provided
the signs of the stresses in the remaining
bars do not change *

Let us consider a figure formed of m
bars, and containing k superfluous lines.
We admit that it is possible in one and
consequently in an infinite number of
ways, by properly choosing the sections, j
to constitute it a system of equal resist-
ance, so that all the bars in tension are j
extended an equal amount per unit of \
length, and all the bars compressed are ;
shortened an equal amount per unit of j
length.

Let w be one of the sections of a su- 1
perfluous bar satisfying the conditions.

Now if we decrease the section %o of I
this bar (which changes its stress corre-
spondingly), the stresses and sections of j
all the other bars will change. If the
signs of the stresses in the other bars
do not vary as we decrease w to zero,
the system still remains one of equal re-
sistance when io=o, or the bar in ques-
tion is removed.

If, however, as we decrease to the sign
of the stress in any other bar changes
from + to — or the reverse, then for
some value of w greater than zero, the
stress in this other bar becomes zero and
its section null, all the other stresses pre-
serving their signs, so that with this bar
removed, the system is again one of
equal resistance. We can thus suppress
one bar after another, until the system is
freed of superfluous lines, provided the
signs of the stresses of the remaining
bars remain the same, and the system
will still remain one of equal resistance.
But for such systems, we have shown
that the total changes of length of each
bar remains the same, however we vary
the sections, the signs of the stresses re-
maining unchanged, as happens in this
case; therefore the figure in question,
after deformation, remains exactly the
same, with or without the superfluous lines,
which proves the lemma as enunciated.

If the signs of the stresses change for
the remaining bars, as we decrease in

* Levy does not assert the last saving clause in his
enunciation.

turn the sections of the superflous bars
to zero, the figure of course no longer
remains the same, after deformation, for
the truss with and without superfluous
bars. Levy has overlooked this impor-
tant fact, which limits his following de-
ductions to a very restricted class of fig-
ures. Thus the following theorem does
not apply to continuous girders of many
panels, braced arches fixed at the ends,
&c, as Levy supposes ; for on eliminat-
ing the superfluous bar or bars the char-
acter of the stresses in some of the re-
maining bars will generally change, and
the elastic deformation is therefore not
the same. In fact, for continuous girders
the chords and web about the center
piers are strained exactly in an opposite
manner to what they are for single spans,
except for the simple case given further
on. If it is possible to eliminate some
bar between the supports that will not
change the character of the stresses of
the balance, then the theory in question
is applicable for such modifications.

§ 9.

As a consequence of the foregoing
lemma, the sum of the work of all the
exterior forces, applied at the joints, due
to the elastic displacement of the joints
is the same for the figure with or with-
out superfluous lines for the case as-
sumed. That is, this sum — call it T — is
a constant.

Let ti represent the positive tension of
a bar, and ai its elastic elongation ; the
work of the exterior forces developed in
this bar, in consequence of the elastic
displacements which produce the elonga-
tion at> is, from a well-known theorem of
mechanics,

i ti a-i •

Moreover, if the system is of equal re-
sistance,

. /

6j — 6ji Wi C ,

whence

a,- = a,;

ei Wi

= at c,

and,

J ti <H = IT ei ai Wi '>

consequently, the sum of the work of the
elastic forces of all the bars which are
elongated, is

326

VAN nostrand's engineering magazine.

The stress of a bar which is compressed,
is

tj =

@j LDj O j

its elongation,

a,- = — CLj C

whence for the work of compression, we
have

i - c"

and for the sum of the work of the com-
pressions,

— 2 aj ej Wj .

The sum of the work of all the elastic
forces of the system, tensions and com-
pressions, is then

c' c"

-jt 2 cti e{ Wi + <r- 2 aj ej Wj = T,

which sum is necessarily equal to the
work T of the exterior forces.

If we regard the material as resisting
tension and compression equally well, so
that c'=c", this equation becomes, re-
garding 2 as extending to all the bars,
whether in tension or compression,

-7r-2aew=T

(24).

If we assume that all the bars have the
same modulus of elasticity e, this equation
becomes

2T
3aw= — tt .... (25).

ec K '

The product aw is the volume of the
bar of the length a; the first number
represents then the total volume of ma-
terial employed, and as the second mem-
ber is the same, for the system with as
without the superfluous lines, we con-
clude :

Theorem III. — When a system contain-
ing k, superfluous lines, is such that it can
in one manner, and consequently in an
infinite number of manners, be consti-
tuted a system of equal resistance, having
the same unit stress for each bar, for a
given loading, there exists always a sys-
tem without superfluous lines, capable of
resisting the same external forces and em-
ploying only the same amount of material,

provided the bars belonging to both sys-
tems retain the same kind of stress, how-
ever we vary the sections of the superfluous
bars towards zero.

Thus, in this particular case, where we
can, without ceasing to employ the same
unit stress, employ figures with super-
fluous lines, there is no economy in doing
so, at least for the loading assumed.

If the bars have different coefficients of
elasticity, we see from Eq. (24) that the
last theorem can be replaced by the fol-
lowing :

Theorem IV. — When a system contain-
ing k superfluous lines is such that it can,
in one manner, and consequently in an
infinite number of manners, by suitably
choosing the sections, be constituted a sys-
tem of equal resistance, for given external
forces, there always exists a system without
superfluous bars, capable of withstanding
the same forces with the same unit stress
as before, such that the sum of the prod-
ucts of the volume of the bars by their
coefficients of elasticity is the same in
this system and the given system for the
special case where the character of the
stresses in the bars remains the same for
the system with or without superfluous
bars.

Now as the sum of the products above
represents in some sort the elastic weight
of all bars, we see that here, as in the
preceding case, that it is not advisable
even when we can, to use figures with
superfluous lines, if the truss is to be
proportioned only for the given case of
loading.

These are remarkable theorems, not
only on account of the simplicity of the
demonstrations, but mainly because of
the generality of the conclusions. It
applies to every form of roof truss, tres-
tle piers, etc., or any structure whatsoever,
whose parts are proportioned to resist the
same unit stress for one kind of loading
and stress in accordance with the hypothe-
sis.

They prove beyond all question, for
such structures, that the system without
superfluous bars is at least as economical
as when they are added.

The theorems likewise apply to bridge
trusses that are designed for one position
of the applied load, as in aqueduct
bridges and in some highway bridges.
For these structures, designed as stated,

TRUSSES WfTH SUPERFLUOUS MEMBERS.

327

there is no economy in the use of any
form of truss whatsoever that has more
lines than are strictly necessary to con-
struct it geometrically.

So we conclude that, even when bridge
trusses with superfluous bars, designed
for one method of loading and stress, can
be modi systems of equal resistanoe,
which moreover rarely happens, there is
no economy in their use if the superflu-
ous bars may be eliminated without
changing the kind of stress of the re-
maining bars, even when we leave out of
consideration the very great influence of
misfits and the effects of settling of the
piers and abutments, &c.

In railroad bridges, and many highway
bridges as designed by some engineers,
we no longer make the system one of
equal resistance for one position of the
live load, but proportion the members of
the truss for the maximum stresses that
may be caused by any position of the live
load, so that Levy's theorem no longer
applies to such bridges.

§ 10.

It may not be amiss to examine the two
cases of systems of equal resistance al-
ready found in relation to Levy's theo-
rem, that the amount of material remains
the same however we modify the sec-
tions, as they afford a striking illustra-
tion of the theorem in question and are
moreover very easily treated.

In the case of Fig. 3 with the top bar
omitted, equations (5) and (6) reduce to
the following, when the two top bars are
supposed to take tension and the bottom
bar compression which, it has been
shown, constitutes this a system of equal
resistance when b = an,

J 'a J'a.

■ • (26)

-/.+/£+/,%-=<> (27)-

Compression and tension are both
plus in these equations.

On dividing these equations by the
common unit stress s, and reducing we
get the following relations between the
sections :

iolaib + w2.2alb=alai— .... (28).
^^.^-w.^-W.^0 • • • (29)-

If we call M the volume of the ma-
terial,

w0a,+w1a1+wiat=M .... (30)

On multiplying (30) by «,a, and (29)
by (a0), and subtracting the latter from
the former, we have

Or reducing, since b=a0, (a* + a02) =
3b\ and (a,9 + <)=668,

'Ma]a,i = 3b[w1aib + wial2b'].

Or since the quantity in the brackets
equals (28), we have

__ 3b lirr

M= — W = a constant,
s

or the material is the same however we
vary the sections according to laws pre-
viously established ; so that we can di-
minish the section of one of the upper
bars to zero, and the resulting volume of
the remaining two bars remains exactly
the same as for the three bars, both
systems being of equal resistance, and
subjected to the same kind of stress.
Mr. Emil Adler, C. E., has kindly com-
municated the foregoing result, as well
as the one pertaining to the next case,
though his method of demonstration is
independent in many respects of the one
followed here.

Let us next consider the very simple
case of a continuous girder of two spans
like Fig. 6 or Fig. 7 below, in which the
figure is made up of isosceles triangles,
and the equal loads are applied at the
upper apices. We have seen that this
system can be made one of equal re-
sistance if the inclined members all take
stress of one kind and the horizontal
members stress of the opposite kind,
provided this supposition is agreeable to
the laws of statics.

Call the equal length of the inclined
members a, and the length of either
span which equals the length of the top
member I, and the height of truss h.
The stresses in the bars will be as desig-
nated in Fig. 7. In consequence of
symmetry, the stresses in corresponding
members, either side of the center are
equal. The equal unknown reactions at
the end supports will be called nF,
whence the reaction of the middle sup-
port is 2P(l-n).

828

VAN NOSTRAND'S ENGINEERING MAGAZINE.

Now regarding tension and compres-
sion as both plus we have for the inclined
members in the compression and the
others in tension,

nV l_
~h 2

■n)

t,=

A=\jfl-*)

having one superfluous bar, we can choose
at pleasure the section of any one bar,
which involves its stress likewise, and by
the aid of the 6 statical equations above
(two each for J\ and J\) determine the
stresses and afterwards the sections of
the other bars. Thus if we assume the
section wx of the outer inclined member,
whence the stress on it is found from the
eq., f-^zcew x, we thereby determine the
reaction nJ? from the first equation
above ; or we may assume nP and com-
pute/*, from this equation and thus de-
termine all the other stresses from the

2P(l-"ri)

Fig.7

These stresses are all plus as assumed,
so long as n= \, as we see from the last

equation, move particularly; so that
when n=^, the system may be made of

equal resistance.

On dividing each stress by the assumed
unit stress s, multiplying by the length
and adding the results, we obtain for
the total amount of material for the en-
tire truss, both spans,

?r Una* + 2a* (1- n) + nl* + l —n?\

This result is independent of n, so that
the amount of material remains the same
however we choose n, provided we do
not exceed the limits o and ^. Thus we
see that Levy's theory is verified for
these two cases of systems with super-
fluous bars, as indeed it must be for all
cases, as it rests upon a strict mathe-
matical basis.

In the case of the last truss, Fig. 7,

group of equations. So that we are
conducted to an interesting property of
this truss, that if we assume the reaction
at pleasure between easily appreciated
limits, deduce the stresses, and design
the sections accordingly for the same
unit stress, that the assumed reaction will
be the actual reaction resulting from the
sections assumed.

Mr. Adler first called my attention to
this principle, demonstrating il in a dif-
ferent and more elaborate manner. If
we make the end reaction zero, the end
braces and lower chord disappears, as we
see from the first and third equations
above. Again if we assume n=^, the
stress ft=o, and the figure reduces to
two discontinuous spans. As shown
above, we have therefore for the same
loading, the same amount of material in
the three trusses, shown in Fig. 8.

We see how marked the influence of
the web is in this example, for by varying
the section of the end brace, which in-
volves a corresponding alteration in all
the sections, we can cause the reaction
to vary from o to J P at pleasure, and
the continuous girder reduces to the
simple bracket, or to two continuous
spans at the respective limits.

TRUSS KS WITH SUPERFLUOUS MEMBERS.

329

§ 11.

We shall next examine a simple form
of roof truss (Fig. 9) given by Bow
("Economics of Construction," p. 84),
especially for the case of an invariable
span, though we shall compare stresses
on the three different suppositions of
truss on rollers at supports with and
without a horizontal bar, and for truss
fixed at supports or span invariable.

On differentiating (1) with respect to <t ^
au, . . . successively substituting in
(3) and reducing, we obtain,

ei"\

W-

e,w,

-V

«.,

a„

((,-. <f

■''."■

r 1

Fig.8

There are 4 joints in this truss and
6 bars, so that m>2?i — 3, and there
is one superfluous bar.

Denote the lengths of the bars AB,
AD AC and DC by 2a,, a2, a3 and a4
respectively and their corresponding
stresses, sections and moduli by fx, w^ e ;

/■> wi> e* ;/g> w* «3 '■> f* ws ev respectively ;
also call h the height of point D above
the horizontal bar AB.

Fig;.9

We have the evident relation between
the lengths,

P= </af-a?-W*;-*?--at=A . . . (1).
From § 4, we draw the following equa-
tions, a,, a2, a3, a4) represent the elastic
elongations of bars AB, AD, AC and CD
after strain :

dF dF dF dF

a + a 1 a 1 a _q

da1 ' da^ a da3 3 daK *

dF ' f dF f dF ft

—aA±- + — a -£i- + — a 3 ^~

aa. 'e.w. aa„ e.w. da. eBw„

which reduces to

OW3— - ( A + a4)a,2 -^- + ha32^-
4 ■ eliol v 4 * eaw9 e3w3

-(A + o4m-^-=0. . . . (4).

We may first inquire if the system
can be made of equal resistance, so that

J 1 J 1

&c.

e2wQ

(2)

= 0

da™\
Vol. XXVII— No: 4—23.

e w
44

(3).

On substituting and reducing, we get
for the hypothesis that all bars are
compressed or all extended, the identity,
0 = 0, as we should § 7 ; but such a sup-
position is not agreeable to the laws of
statics.

If we suppose all the bars in com-
pression except AB, so thatjf, f% andjf4
are minus, and/*, plus eq. (4), reduces to
the absurdity, aia]2 = o. Similarly the
supposition that fz is minus (compres-
sion) and fx, f2 and f4 plus (tension)
causes an absurdity.

These are the only reasonable sup-
positions that can be made as a stress
diagram will show ; so that the system
cannot be made one of equal resist-
ance.

Let us now ascertain the stresses in
the frame for a weight of 2 tons rest-
ing on the summit, the ends of the truss
being free to move, on imaginary per-
fect rollers, the lengths being taken as
follows: a, = l,000. aa = l,118, a3 = 1,414,
a4=500 and h =500, and the sections of

330

YAN NOSTRAND'S ENGINEERING MAGAZINE.

all the 3 bars being taken the same, as
well as their moduli.

We must frame our equations upon
the supposition (already made in 4)
that all the bars are in tension, so that
the forces due to the bars act away from
any joint considered. The reactions are,
of course, 1 ton each and act upwards.
Upon solving the equations, we of course
find the proper signs for the stresses,
plus corresponding to tension, and minus
to compression. Expressing now that
the sum of the horizontal and vertical
components of the forces acting at A are
separately equal to zero, balancing the
vertical components of the stresses in
the bars meeting at D, and substituting
the numerical values in (4), we get the
four following equations to determine
the stresses in the four bars.

find by elimination, the stresses, which
are as follows :

/,= + 1.306 tons.

Acting inwards as assumed, otherwise
the sign would be different,

f9=— 0.67 tons (compression.)
/8=— 1.00 "
/4=-0.6 "

^00 1000

1118*

1414'

• (5)

1000, 1000,
/i+ttiq/. + i7T7/>=0 .... (6)

1118*

1414

2-^f-f-O
1118*72 Ji

2/1-5/. + ±/i-/4 = 0

.... (7)

.... (8)

By successive elimination, we deduce
the following numerical values :

^=+1.17 tons (tension).
f^= —0.39 " (compression).
/,= -1.17 "
f = -0M «

As the sections were taken equal, the
unit strains for all the bars varies as
the stresses above.

Let us next ascertain the stresses for
span invariable, so that ai reduces to
zero in Eq. (2) whence (4) becomes for
equal sections and moduli

On combining the vertical component
of the reaction = 1 ton, with the hori-
zontal component = 1,306 tons, we find
the resultant reaction, whose position
thus lies between that of the two inclined
bars AC and AD.

We may next find the stresses for this
truss with the horizontal bar left out,
supposing the truss to rest on friction-
less rollers, so that the reactions are ver-
tical. The stresses as found from a dia-
gram are :

f%= +2.236,/; = -2.828and/4= + 2.tons.

Let us tabulate these results, for a
weight, resting at the summit, of 1,000,
so that the changes the stresses undergo
for the different suppositions may be seen
at a glance :

-5/, + 4/r-/= 0.

(9).

The horizontal bar AB must now be
removed, as it cannot change length,
and consequently cannot suffer strain,
and we shall suppose horizontal forces fy
acting inwards at A and B to repre-
sent the horizontal components of the re-
actions, the vertical components remain-
ing as before.

Equations (5), (6) and (7), under this
supposition, still hold, so that from
these equations and Eq. (9), we are to

Truss on

rollers.

Bar AB

removed.

/, = + 1118
/8 = -1414
/4 = + 1000

Span

invariable.

Bar AB

removed.

/s = -335
/a = -500
/4 = -300

Truss on
rollers.
Bar AB
retained.

/1 =+585
/8 = -195
/3 = -585
/4 = -175

In the first case, where statics alone
determines the stresses in the bars, we
can suit the sections to any unit strain,
but in the other two cases the sections
were all supposed equal and the unit
strains vary very greatly. We have just
seen that it is impossible to make them
equal, for this truss ; but we may ap-
proximate nearer to this result by choos-
ing different sections and computing
strains and so on ; in other words, by a
laborious tentative solution.

This example will give some idea of
how strains are materially affected by the
condition of the supports, which are
probably never exactly as assumed.

In this connection we shall give Bow's
method of finding the reactions and

TRUSSES AVITII SC PKKFLUOUS MEM 1? Kits.

331

stresses for any assumption regarding
the yielding of the support, or for span
invariable. This method is in brief "to
assume in succession two different direc-
tions for the reaction of the abutment
and calculate for each the change caused
in the length of the span ; the reaction
or supporting force that will cause no
change of length in the span is then eas-
ily ascertained by taking for its com-
ponents such proportions of the two as-
sumed reactions, that their effects in al-
tering the length of the span will neutral-
ize one the other." If a certain change
of span is assumed, the reactions could
be found in a similar manner.

Assuming the weight resting on the
summit as 1,000, Bow finds, for the reac-
tion vertical and equal to 500, the change
of span = + 0.1, and for two horizontal
forces, acting inwards at both abutments,
each equal to 500, the change of span,
-4.7; so that the ratio of the true horizon-
tal component to the vertical reaction to

cause no change of span is -^-=1.3,

which agrees with what we have found
above in an entirely different manner.

Bow does not state how these changes
of span are computed, but we readily see
that it may be effected by aid of eq. (2)
above, or for this particular example from
(4) modified as below:

«,"A-(^ + «>,2— +ha*fi

e2v>,

— (h-{-ai)hai

/<_

As we only desire relative changes of
span, we can put

«st01=eiw8=«4t04=lOO,

for ease of computation, so that the above
equation becomes, on substituting nu-
merical values,

«,=25/,+20/,-5/,

By aid of a stress diagram, we find
for reactions vertical,

/,= + 1118, /,==+ 1414,

/4=+iooo,

al=61,230.
For the truss subjected only to the two

and
whence

horizontal forces, taken equal to the ver-
tical reactions just mentioned, we find

/;= -1118, /,= +707,
/4=-1000,

a, = -47,090,

so that the ratio of the horizontal to the
vertical component of the reaction is,

61,230

and
whence

47,090

:1.3, as found above.

This method may be preferred in some
cases to the preceding, and in all cases
should be used as a check.

§ 12.

We have now given the general meth-
od to be followed in treating frames with
superfluous bars, and illustrated the sub-
ject by some of the simpler examples.
The solution becomes more and more
complex as the number of members of
the frame increases, besides it is general-
ly impossible to constitute trusses, hav-
ing many subdivisions, systems of equal
resistance, even for one given case of
loading. American engineers generally
have wisely avoided such systems and re-
stricted themselves in practice to trusses
whose parts can be computed by the sim-
ple laws of statics and that can be made
systems of equal resistance, if desired,
or whose parts can separately be sub-
jected to any unit stresses that experience
has approved. Thus most of our roof
trusses can be statically determined ;
also the single intersection bridges as
the Pratt and Howe types ; for it has
been shown (§ 5) that the counters (which
are superfluous bars, if in action at the
same time as the main diagonals) are not
in action when the corresponding main
diagonals are in action and vice versa, so
thai the number of bars (m) under stress
at the same time remains constant and
equal to, %i — 3, where ?i= number of
joints, as may be readily verified.

The same relation, m = 2n— 3, will be
found to hold for the Warren girder and
modifications, the bow string, Schwedler
and other single intersection systems,
and systems whose diagonals are not
crossed and which can take compression
and tension both for certain panels. The
Fink truss, too, will be found to be stati-

332

VAN NOSTRAND7S ENGINEERING MAGAZINE.

cally determined, as well as the Bollman
when the panel diagonals are left out.

But for double intersection bridges it
seems impossible to prove in some cases
that the number of bars under stress re-
mains constant for any loading and equal
to 2n— 3, or the number of bars when
the counters are omitted ; so that the
common supposition to that effect is not
strictly accurate.

Thus in the double intersection quad-
rangular deck truss below (Fig. 10), where
the two partial systems into which the
truss is supposed divided, are marked
with heavy and light lines respectively, let
us suppose a live load to extend from the
right abutment to joint 7, and that coun-
ter G5 is in action, which consequently
throws E7 out of action, similarly E3 is in

the reaction at A for the whole truss, and
subtracting the loads on one system up
to the point of greatest deflection to get
the reaction for the other partial system ;
but as we cannot fix this point of great-
est deflection the indetermination still
exists. The difference between the true
and common methods is probably slight,
for well-fitting trusses with counters
properly adjusted, and the method in
vogue is likely on the side of safety ;
still it is to be regretted for this popular
form of truss that any indetermination
should exist as to the stress in the mem-
bers.

It might be thought that a trellis
bridge, whose diagonals can take tension
and compression both, was free from the
defects of the preceding truss, but we

action and C5 out of action* so that the to-
tal number of bars under stress in the one
partial system shown by the heavy lines
remains the same. But on considering
the other partial truss, the dead load at
F may go partly by F8 to right abutment
and partly by F4 to left abutment. If
F4 is strained, D6 is not ; still if F4 and
F8 are both strained at the same time,
the truss will be found to have one su-
perfluous bar, so that it is statically un-
determined for this particular loading ;
for the number of bars is now 30, and
the number of joints 16, so that m ex-
ceeds (2/i — 3) by one.

The common supposition is that the
dead load at F goes to right abutment,
but it is unproved and is incorrect if the
greatest deflection of the truss is at G,
for then all diagonals to the left of G,
parallel to G5 are under tension and the
diagonals crossing them are shortened
and thus out of action; so that under
this supposition F4 is in action and F8
out of action. There are thus two horns
to the dilemma, either the system may
be statically undetermined or the com-
mon theory is not strictly correct. The
most correct solution consists in finding

shall not find it so. In fact for a trellis
truss of eight panels, we have, m = 30
and ?i=16, so that ra>2n— 3=29. and
the system is statically undetermined.

It may not be amiss to notice here an
opinion entertained by some, that a mis-
fit in a diagonal eye bar say, would cause
extra strains over those computed equal
to the force required to stretch the bar
to its calculated length, which may
amount to . several tons strain to the
square inch. It is hoped that the fore-
going discussion has demonstrated that
for statically determined systems, with
joints free to move, that the usual misfits
has no influence on the strains. If the
joints are not free to move, as in the up-
per joints of some bridges, or if the- sys-
tem has superfluous bars, the strains are
not as computed, but even then there is
no simple relation like the above to ascer-
tain the extra strains. It is known that
even with pin connected bridges, there
may be sufficient friction at the joints or
imperfect action of the rollers to disturb
the strains given by statics alone on the
supposition of perfectly free joints ; but
leaving this to one side, it is evident that
as pin connected trusses, without super-

TRUSSES WITH SUPERFLUOUS MEMBERS.

383

fluous bars, can be corbelled out piece by
piece from one end, as was done in the
Kentucky River Bridge (C. S. Ry.) that
every piece must come to its bearing,
and there can be no extra strains from
misfits that are appreciable.

§ 13.

FRAMED PIERS.

Framed piers and trestle bents have
often either a lack or a redundancy of
parts or both, so that the stresses in them
cannot be determined by statics alone,
except perhaps for a uniform vertical
loading.

Of late much more attention has been
given to wind pressure on piers than
formerly, resulting in simple forms that
statics can handle. It will be the prin-
cipal object of this section to treat such
forms fully (especially as, so far as the

centrated on the lower chord will act be-
low, whilst the components acting on
the upper chord and car surface, will act
above the upper member of the pier.

The position of H can readily be found
by equating the sum of the moments of
the wind pressure acting on the upper
and lower chords and car surface about
the top of the pier with Hy, giving, say
a positive sign to a left-handed moment,
and a negative sign to a right-handed
moment. The resulting sign of y will
show whether H acts above or below the
top of pier.

If we add now the two equal and op-
posed forces, H,, H2, acting along the top
member, whose length is x, we do not dis-
turb equilibrium, but the single force H
is now replaced by the couple HH,, and
the single force H, acting against a mem-
ber that can sustain it.

Fig.11

writer knows, they have never received a
thorough and accurate analysis), as well
as to discuss other well-known designs
with a view principally to pointing out
their defects and of analyzing some of
them.

Let Figs. 11 and 12 represent one bent
of a framed pier, subjected to the total
wind force H on trusses and train, sus-
tained by it, acting at its center of press-
ure, a distance y above (Fig. 11) or be-
low (Fig. 12) the top of the bent.

Where the pier sustains a through
bridge or a deck bridge supported at the
lower chord, H will always act above the
pier, though it may happen otherwise
when the pier sustains a deck bridge
swung from the top chord. In the latter
case the component of H, supposed con-

Fig.12

Now if the equal vertical forces W, and
W2, acting in opposite directions at the
tops of the inclined columns where they
can be sustained, are of such a magnitude
and direction that,

W1x=Wix='Ky,

then the couple W,W, can replace the
equal couple HHj ; so that we have finally
as the equivalent of Hj the forces H2, W,
W2, all acting along members capable of
sustaining them.

In Fig. 11 as HHj and consequently
l Wj W2, are left-handed couples, W( acts
| to increase the weight on the leeward
column and W2 to decrease the weight on
the windward column. The reverse ob-
tains for Fig. 12.

334

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

The reactions Ba and R2 are readily ob-
tained by equating the moment of the
couple R^ with that of the couple HH3
=HX height above lower sill.

The reactions are however readily found
from a stress diagram without any com-
putation whatever.

Generally these framed piers consist of
two bents braced together, so that the
total wind force on one bent is one-half
that on the trusses and train on the adja-
cent span. The same holds for the out-
side bents, where the pier is composed of
any number of bents braced together,
though in this case the other bents
will materially assist if overturning of the
outside bents is about to take place. Still
it is proper to design these outside bents
on the supposition that they receive no

In the following figures one set of
diagonals are left out, since the truss, on
distortion sideways, will bring one set into
action only, as these diagonals are usually
made of bars of such small section that
they cannot take an appreciable com-'
pression.

§14.

Having found, as just shown, the forces
W,, Wa and H2 due to wind force alone,
and added, with the proper signs, the ver-
tical loads due to the weights sustained
by the pier, we can now proceed to draw
the stress diagram Fig. 13 (b). Bow's
admirable notation is used by which a bar
or a force, in Fig. 12 (a), is designated by
the letters between which it is placed and
the stress on the bar or the magnitude

aid whatsoever from the interior bents,
especially if none of the columns are to
be subjected to tension which is ordina-
rily good practice.

When the pier consists of but one bent
only, the wind force on it is that caused
by the wind acting on one-half of trusses
and train on both adjacent spans.

Exactly the same relations hold as to
the weight of trusses and train sustained
by bents, disregarding the wind, so that
it is very easy to compute for trusses
loaded or unloaded the total resultant
vertical forces at top of columns, as well
as the horizontal force H due both to the
weight of trusses and train and to the
wind acting on them.

"We shall suppose this done in what
follows.

Fig. 13

of the external force is shown, in Fig. 12
(b) by the lines, to scale, at whose ends
are the same letters. Thus the external
forces due to the weight of the trusses
and train and the wind force acting on
them are given in position in Fig. 12 (a)
by GH, HI and LG, and in magnitude,
to scale, in Fig. 12 (b) by the correspond-
ing lines GH, HI and LG. The reactions
are similarly represented by JI, KJ and
KL. In (b) these forces taken in any
order and true direction, should form a
closed polygon LGHIJKL, as obtains
here.

On drawing in (b) the sides HA, AB,
. . . , parallel to HA, AB, . . . , in (a), we
form the stress diagram in which the stress
in any member as AB in (a) is given to
scale by line AB in (b). These stresses

TRUSSES WITH SUPERFLUOUS MEMBERS.

335

are tensile or compressive, as in follow-
ing around the polygon for each joint in
the proper orde*r, the force acts away from
or towards the joint considered.

In this figure, for the proportions and
forces given KL is a downward reaction,
so that a holding down bolt is requi-
site.

As a rule, American engineers give suf-
ficient spread to the base, so that no ten-
sion is exerted in the windward column.

We notice here, as in the next figure,
that on constructing the stress diagram,
beginning at the top of the pier, we find
the reactions without any computation,
though they may be tested as well as any
of the stresses by the method of mo-
ments.

an able paper by C. Shaler Smith, and
discussions thereon in the transactions of
the American Society of Civil Engineers,
for Dec. 15, 1880, and republished in En-
gineering News for Oct. 1, 1881.

Mr. Smith gives the following specifi-
cation for piers : " Iron piers and spans
carried by them shall be designed to re-
sist a wind force of 30 lbs. per square
foot on train and structure, or 50 lbs. per
square foot on the structure alone.

"The compressive strains on the lee-
ward columns of the piers shall be com-
puted with the assumption that the maxi-
mum load is on the bridge, and to these
shall be added the compressive strains
produced by the wind, and the columns
shall be proportioned to resist these com-

I J K L

Fig.H

, X /

P\ Q\ R \J

\ cs\ B

E^\^

(b)

If the pier is of such a height that it
would be unsafe to neglect the force of
the wind blowing directly on it, we must
ascertain the horizontal wind force acting
directly at each apex, when the stresses
are quickly found from the following dia-
dram, Fig. 14 (b).*

The force polygon here which is closed,
as it should be, is Fig. 14 (b),

GRQPONMLKJIHG.

We shall find for this figure, that a
holding down bolt is necessary and that
the segments EP and CQ of the wind-
ward column are in tension, AE. being in
compression, whilst for the previous fig-
ure, the lower segment LE is in tension.

As to the amounts of wind pressure
per square foot allowed in practice, see

*The weight of pier is similarly included in any
stress diagram, by combining the proper weight at
each apex with the wind pressure.

bined strains with a factor of safety of
four. The minus strains on the wind-
ward column shall be computed with the
lightest train on the bridge, which will not
be blown off by a wind force of 30 lbs. per
square foot, and such a width of base
shall be given to the pier that there shall
be no tension in any of the columns com-
posing it."

The pressure of 30 lbs. per square foot
was specified principally because empty
cars are blown over at that pressure. A
higher pressure than 50 lbs. on the struc-
ture alone has been advocated by some

J engineers. It is evident, too, that in

i some situations it may be well to design
the pier to resist tension in the windward

1 column for the maximum wind pressure,
but as a rule it is not advantageous.
The form of truss given in the preced-

: ing figures, without superfluous bars, is

336

VAN NOSTRAND'S ENGINEERING MAGAZINE.

that most generally adopted now for iron
piers, and no better can well be devised
either for single or double track railways.
The piers for Mr. Shaler Smith's Ken-
tucky Kiver Bridge are of this form, only
the tops of the two bents are drawn to-
gether and vertical struts extending from
the bottom upwards to the first horizon-
tal member below the top one, give a sup-
port merely at the middle of these hori-
zontal compression members, which does
not disturb the strains as given by
statics alone.

§15.

A form of pier, shown by the following
figure, only with two sets of diagonals,
in place of one as shown, has been pro-

Fig.15

posed for double track railways ; but the
system is faulty in having superfluous
lines.

Thus for the number of divisions shown,
we lhave ?i=9 and ra = 16 v 16>18— 3
= 15, and we have one superfluous bar.
Therefore to compute the strains arising
from any given loading we must write
that at each joint the sum of the hori-
zontal components of the forces, includ-
ing the stresses, are zero, and that the
sum of the vertical components are zero.
This gives 18 equations or 15 indepen-
dent ones. The additional equation is
found by considering any one of the right
triangles, whose hypothenuse has a length
av and the other sides the lengths aa and
a8 respectively, so that we have the rela-
tion,

whence, as previously explained, we de-
rive,

and,

ew.

,/,

ejo„

+ a,

eaw„

This last equation added to the others
furnished by statics gives 16 equations to
determine the stresses in the 16 bars.

The next figure (16) has the main com-
pression members in the shape of an in-»
verted W, and suffers even more than the

Fig.16

previous truss from superfluous bars.
Half of the diagonals are supposed out
of action from the side pressure; but,
even then, we have, wi = 17 and n=9, so
that we have, m— (2w — 3) = 17 — 15=2
superfluous bars.

Consequently to the 15 independent
equations of statics we must add two
equations resulting from the geometrical
relations between the sides. Thus con-
sider one of the triangles above, whose
sides have the lengths, al9 «a, a,, respect-
ively ; the acute angle formed by the
sides a% and as being desigated by 6, we
have the well known relation,

F = axa — a22 — a8a + 2a2a9.cos0 = 0.

On giving the sides the increments in
length a,, a2, a3, and subtracting the first
equation from the second, neglecting dif-
ferences of the second order, we obtain,

^A- (ai — ascosd)a2— (as — «2cos#)«3 = 0.

On substituting the values for a=* — we

obtain one of the required equations.
Similarly the other is obtained by con-
sidering one of the other triangles, so
that as many equations as bars can be
written and the stresses in those bars
determined by elimination between the
17 equations.

The labor of ascertaining the stresses
even for as few divisions as we have taken
is very great and is enormously increased
for high piers with many subdivisions of
the columns. It is more than probable
that with the column material concen-

TRI rSSES WITH SUPERFLUOUS MEMBERS.

337

trated in the two outer braces, that not
only would the strains be easily deter-
mined, but the pier would be materially
lighter. At any rate, it is doubtful if a
correct method of calculation has ever
before been applied to these piers with
superfluous members, so that no correct
comparison has been made between them;
but the writer is far from recommending
them, even if they should show economy,
as the strains are subject to such wide
alterations from misfits, settlements of
the foundations, heat of the sun on one
side, etc., that any apparent economy is
not real and only misleading.

tensile resistance at the mortise joints, so
that we can safely assume that certain
pieces that would otherwise be in ten-
sion, are out of action and the computa-
tions because very much simplified and
possible in some easos by statics alone.

The adjoining figure gives a skeleton
outline of the most common trestle bent

16.

The forms so far considered are about
the simplest that have been used in iron
construction. The more complicated
forms are objectionable in so many re-
spects that they should unhesitatingly
be condemned. Of such objectionable
types are those piers whose bases are not
rectangular as we have assumed hither-
to, but six or eight sided ; so that the
whole pier with its internal bracing must
be considered if any attempt is made to
design them scientifically. The six sided
base, shaped like an ordinary masonry
pier with cutwaters, is about as bad a de-
sign as co aid well be imagined where
wind pressure is concerned. It is no
wonder that the Tay Bridge piers, which
were of this design, failed when subjected
to a strong side wind with the train pass-
ing at the time, probably from weakness of
the internal bracing which was designed
by some rule of thumb method. To com-
pute the strains in such a structure, it
would be necessary at each joint to ex-
press that the components of the forces
and stresses in the directions of three
rectangular axes were separately equal to
zero. As there are six necessary re-
lations between the external forces, the
number of independent equations reduces
to 3// — 6. To these equations we must
add m — (3?i — 6) equations derived from
the geometrical relations of the sides, from
all of which the resulting stresses for ^.s--
mm^d sections can be found and the unit
stresses determined.

I 17.

We shall conclude this discussion by a
consideration of trestle work and trestle
piers in wood, which can offer but little

Fig.17

in wood, with posts vertical and braces
inclined from 3 to 5 inches per foot. If
the weight of bent is neglected, we
simply combine weight of cars for dis-
tance between bents, center to center,
with the horizontal force of wind acting
at its center of pressure to get the re-
sultant shown by the arrow acting at the
cap sill. If this falls between a post and
brace as shown, as will happen ordinarily
for a 30 lb. pressure on empty cars
when the batter of the brace is 5 to 12,
the bent is stable and the whole weight
is sustained by these two columns. If the
posts are spread further apart so that
this resultant passes between the posts
the vertical component is divided be-
tween them according to the law of the
lever, but the horizontal component act-
ing along the cap must all be sustained
at the left, as the right brace and post
cannot receive tension ; so that at the
intersection of the center lines of the
post and brace (when not far apart) we re-
combine the horizontal component or
thrust of wind with the vertical load
sustained at the left post for the total
resultant, which may then be decomposed
following the center lines of post and
brace. If this resultant passes outside
the brace the bent is unstable as the
post cannot receive tension.

For this form in iron, the horizontal
component acting along the cap is sus-
tained equally at the two apices, since

338

VAN NOSTRANDS ENGINEERING MAGAZINE.

any horizontal movement of the cap
affects both to the same amount, and
since the figures formed by the post
brace and base sill are similar, right and
left, the small deformation and resulting
strains are the same for both figures.

Where the weight of bent and track is
considered, in addition to the weight of
train and the side pressure of the wind,
we simply combine the weight of bent
and track sustained at a post with the
vertical components of the train and wind
load conveyed there, for the total vertical
component, which combined with the
wind pressure gives the resultant re-
quired.

For the usual sizes of timbers and
bents 12 J feet from center to center, we
find that a batter of 4 to 12 will ensure
sufficient stability, and even less may be
used though it is not advisable.

§ 18.

This form is not so good as the follow-
ing, the inverted W, though the latter is
a little more troublesome to frame, which
is sufficient with some engineers to con-
demn it.

In this bent, part (say half .ordinarily)
of the horizontal thrust H can be com-
bined with the weight resting at each
upper apex to find the resultants Rt and
R2 acting at these apices. If R: and R2
are inside their respective angles, the
bent is safe, if the columns are of suf-
ficient strength to sustain the respective
components of these resultants.

Fig.18

If Rx passes outside the left post by
this decomposition, we must increase the
horizontal component of R2, so that Rx
will give compression on both the posts
that sustain it. If both R, and R2 pass

outside their respective supporting col-
umns, the bent will be destroyed. It
is evident that for the same stability of
piers the outside columns can have a less
batter than the braces in the preceding
figure.

We see how very erroneous it would
be to apply the usual method of testing
the stability of solid piers to these
wooden structures, for such methods
suppose the pier to act as one piece in
overturning, whereas in the wooden
trestles if a destroying force is exerted,
the bent will not overturn as a whole,
but the posts and braces that would
otherwise be in tension pull out of the
mortises and the bent collapses by the
cap descending sideways to the ground,
the posts rotating about their feet as
centers.

§ 19.

The previous figures for wooden bents
(17 and 18) are used for heights of 10 to
25 feet say. As the only objection to
such simple forms is the danger from
flexure of the pillars it is very common
to spike an X bracing as in Fig. 19, not
only as a guard against flexure, but like-

Fig,19

wise to give such solidity to the frame
that it would tend to overturn as a whole
and not by parts.

Of course this is theoretically a bad
type, but it is very efficient practically.
The stress on the cross bars may be
taken very approximately on the assnmp-*
tion that -only one bar acts to resist by
tension the overturning effect of Rx
which passes outside the outer brace.
If we call I the perpendicular distance
from the foot of this brace to the direc-
tion of Rj and a -the lever arm of the
cross piece about the same point, we

in the cross piece =-

have, the stress

The size of the piece and spikes that at-
tach it to the posts and sills should be

TRUSSES WITH SUPERFLUOUS MEMBERS.

339

proportioned to resist this strain. For
greater heights of trestle, several bents
are superposed, one above the other,
forming a 2 deck, 3 deck, &c, trestle.
Figs. 20, 21 and 22 represent forms of

/
/

Fig, 20

Fig.21

Fig.22

this kind. These types may be ex-
tended to any height. The size of the
timbers is generally uniform from top
to bottom, so that if it is sufficient to
carry the whole loading at the top, after
previous decompositions, there need be
no fear of want of strength in the lower
bracing where the strains are divided
up amongst a greater number of pieces, so
that a strict computation is unnecessary.
I suggest Fig. 20, which I have never
seen used, as a preferable form to either
of the other two.

Trestles are not generally sufficiently
braced longitudinally or in the direction
of the axis of the road. The most
efficient form is X bracing, spiked on and
extending from bent to bent. I have
been informed that a 4 mile trestle only
15 or 20 feet high, without any longi-
tudinal bracing was — the whole of it —
knocked down by a freight train striking
it in a certain manner at one end.

I have not mentioned the trestling,
whose bents are formed of two piles, 6 to
8 feet apart, projecting out of the ground
and capped for the stringers to rest on,
because the force of the wind is here
principally resisted by the resistance to
cross breaking of the piles, though X
bracing is generally added both trans-
versely and longitudinally to make a
stiffer structure. This form is especially
adapted to wide swamps, where a pile
driver on a flat car is constantly on hand
to repair damages, and likewise to all
temporary trestling over soft ground.

From what has preceded, we see that
we are much safer in using an approxi-
mate solution for wooden than for iron
piers with superfluous bars. In fact
from the rough manner in which the
framing is done for wooden piers or

trestles, it would be folly to assume a
perfect fit throughout, without which
any refinement of calculation is indeed
" superfluous."

For iron piers, where it is desirable
and practicable to proportion the sizes of
the pieces to the stresses they have to
bear, the truss without superfluous
members is to be recommended, as the
unit stresses can be assumed at pleasure ;
but for trusses with superfluous mem-
bers, we have seen that it is very rarely
the case that they can be made of equal
resistance, so that in nearly all cases in
practice we should have to assume the
sizes of the members and then find the
unit stress on each member : then as-
sume other sections that will probably
more nearly equalize the unit stresses
and so on, until the unit stresses are
brought within reasonable limits, even
though it may be impossible to give
them exactly the values that are prefer-
able. To this difficulty is to be added
the influence of misfits, settlement, &c,
in altering very materially the computed
strains, so that trusses with superfluous
members are not to be recommended ex-
cept in rare cases, for which it is hoped
the preceding treatment is sufficiently
full to answer the demands of prac-
tice.

REMARK.

Since the above was written, an article
has appeared in the September number
of this Magazine, on " The Resistance of
Viaducts to Sudden Gusts of Wind," by
Jules Gaudard, translated, &c.

The usual error is made, in ascertain-
ing the stresses in Fig. 4, in not finding
the excess of weight thrown on one col-
umn of the pier, and the diminution of
weight on the other column caused by
the wind pressure on truss and train.
We have so fully explained the proper
method above, that only involves the the-
ory of couples, that it is needless tc at-
tempt to make the proof plainer.

Gaudard gives the horizontal wind
pressure on pier from truss at 20 tons,
acting at a height of 13.1 feet above top
of pier, and the corresponding wind
pressure on train as 16.2 tons, acting
27.2 feet above top of pier. As a conse-
quence the excess vertical load borne by
the leeward column, is

340

TAN NOSTRAND'S ENGINEERING MAGAZINE.

16.2x27.2 + 20x13.1

= 52 tons,

13.5

and the same load must be subtracted
from that due to weight of truss and train
borne by the windward column. Now

column 109.25 tons, and at the top of
windward column 5.25 tons, both acting
downwards.

The total wind pressure,

16.2 + 20=36.2 tons,

the weight of loaded roadway borne by
each column is 51.25 tons, to which add
6 tons for the weight carried at each up-
per apex, giving 57.25 tons. From this
add and subtract 52 tons, giving the re-
sultant vertical load at top of leeward

is transferred now to the top of pier, act-
ing along the top member, by the couple
supposed, so that with the other data
the stress diagram is quickly drawn.

As a proof of the incorrectness of
Gaudard's analysis, he gives as the wind

THE ELECTRICAL TRANSMISSION OF ENKKi IY.

341

pressure acting on train 16.2 tons, on
truss 20 tons and on pier 20 tons, total
56.2 tons, whereas at the base of pier, he
supposes a horizontal reaction of 60.04
tons, which therefore cannot balance the
total horizontal wind force as it should.

As the scale is too small to give the
stress diagram for this Bouble viaduct
very clearly, we append a figure, having
some resemblance, with the stress dia-
gram drawn for the forces assumed.

For this pier, the weight supposed
concentrated at each apex is combined on

the windward side with the correspond-
ing wind force. The other forces are
found as before.

The closed polygon of forces is,

JKLMABCDEFGHIJ.

The character of the stresses is as
marked on the figure, -f for tension,
— for compression. This is not so good
a form for a bridge pier as one with
straight columns of sufficient batter, as
a greater number of segments of the
windward column are under tension.

THE ELECTRICAL TRANSMISSION OF ENERGY.

By MAURICE LEVY.
Translated from Annates des Ponts et Chaussees for Van Nostrand's Magazine.

In the transportation of energy, the
end to be accomplished is this : — Having
at a certain locality A, a permanent source
of energy under any form, either mechani-
cal, chemical or calorific, it is desired to
utilize it under the same or any other
form, at some other place B at any dis-
tance from A.

Suppose, at first, that the two points
A and B are connected by a simple cir-
cuit.

We should place at A an apparatus
capable of producing an electrical cur-
rent by means of the energy existing
there. This would be a magneto or dy-
namo-electric machine if the energy were
mechanical ; a pile of it were chemical,
etc.

At B, on the contrary, we should place
an apparatus capable of receiving the
current and transforming it into the form
of energy we desire to obtain. It might
therefore be an electric motor, an electro-
plating bath, an electric lamp, etc.

Let Tm be the work furnished per sec-
ond by the apparatus generating the cur-
rent, and which we will designate the
motor work, and let Tu be the work af-
forded per second by the receiving ap-
paratus, and which we will call the useful
work.

The apparatus A receiving energy be-
comes the' seat of an electro-motive force,
such that it reproduces in the circuit ex-
actly the amount of energy received from
without.

Now, if in accordance with Joule's law

we designate by E the electro-motive
force and by I the intensity of the cur-
rent, supposed constant, the quantity of
work per second will be E I. As this is
also the work received by A, we have

Tm=EI .... (1)

The apparatus B producing an exterior
work TM becomes the seat of an electro-
motive force E', directed in such way as
to lessen the energy of the circuit by
the amount of work produced outward.
It is necessary then that this force act in
a direction contrary to the current. The
quantity of energy removed from the
circuit will be EX Such is also the
work produced by the apparatus, and we
have

Ttt=E'I .... (2)

Furthermore, the action being sup-
posed established, the law of conserva-
tion of force teaches us that the motor
work is equal to the useful work plus the
work expended in heating the circuit.
Now if S is the total resistance of the
circuit, composed of the resistances of
the generator, the receiver and the exterior
circuit, the work according to Joule's
law is SI2. Therefore,

Tm-TM=sr

(3)

These three simple equations are all
that is necessary. As has been already
shown by the writer in communications
presented to the Academy in November,
1881, these equations permit us to study
all the important consequences of the

342

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

transportation of energy, whatever the
form of energy, and whatever the nature
of the apparatus or machines employed
in the operation. They contain in all six
quantities :

T T

E E'

I S

If three of them are known the other
three may be found.

Suppose there are given S, the total
resistance; Tu the work to be obtained,
and E the electro motive force of the
generator. Then the unknown quanti-
ties are : Tw„ the work of the generator,

the ratio of the work obtained

from B, to the work expended at A (ef-
ficiency) ; the intensity I of the current ;
and the electro-motive force E' which is
manifested at B.
The values are :

E±A/E2-4ST,

2S
t EzFA/E2-4STt

^— — -lie 14/1

4STt
E

In order that the operation be possible,
that is to say, that a current should ex-
ist, it is required that

s<5t;

Thus the greatest resistance S, against
which a given amount of energy Tu can
be transmitted by means of the electro-
motive force E, is :

The resistance increases as the square
of the electro -motive force of the gener-
ator ; but this electro-motive force itself
cannot be increased indefinitely. There
is a limit beyond which the circuit can-
not be insulated. Let E0 be this limit.
The corresponding maximum value of S,
is:

There exists therefore for a resistance

against which we can transmit a given
quantity T„ of energy, a limit which we
cannot pass, however great the mechani-
cal force at our command, and however
powerful the electrical motors engaged
in the transmission.

Beyond this limit the power of the ma-
chin e produces no current, nor in conse-
quence any work in the receiving appa-
ratus, but electric sparks along the cir-
cuit. In the same manner there exists
for the power of traction of a locomotive
a limit which depends only upon the
weight on the driving wheels and not
upon the power of the engine, and be-
yond which the force exerted by the
steam produces only slipping of the
wheels, and not motion of the train.

Suppose the value of the electro-mo-
tive force to be E, a little less than, or at
most equal to E0. Then the operation
would be possible provided that

or S:

If S be taken at this latter value, the
preceding equation gives

2S'
and for the efficiency

If we take

=*•

4TW

we get two solutions.

By using the superior sign we get :

and for the efficiency,
— <i

T\2«
m

♦

To obtain the values given by taking
the lower signs, it is necessary to reverse
the above signs of inequality. The solu-
tions giving real values indicate that we
may have a strong current with low effi-
ciency or the reverse.

In the following, the condition of best
efficiency will be assumed. Taking there-
fore the second values, referred to above,
we have :

THE ELECTRICAL TRANSMISSION OF ENERGY.

84:*

E-VE*-4STtt
2S

E + VEa-4STtt

(5)

T„ E' r Ea

T~E = 2

(6)

From this formula we deduce important
conclusions.

It is readily seen from the. above that
the efficiency is not independent of the
quantity of energy TM to be transmitted. !
It becomes, other things being equal,
less as the energy becomes greater.

Thus when we speak of efficiency in
the transportation of electrical energy, it
is indispensable that the amount of en-
ergy to be transmitted should be speci-
fied. If twenty-horse power are to be
transmitted we shall have, other condi-
tions remaining the same, a lower effi-
ciency than if we get ten-horse power.

It is from a defective understanding
of this point, that a correct statement,
made by M. Marcel Deprez, in a paper to
the Academy of Sciences (March 15th,
1880), has been poorly comprehended,
and proved an exciting cause of contro-
versy both during and after the meet-
ing.

After having obtained the expression

for efficiency = , M. Deprez expressed
xLi

himself as follows : " A remarkable ex-
pression, as it is independent of the re-
sistance of the exterior circuit. It seems
extraordinary at first sight, and even
contradictory to experience in some cases,
unless the conditions of maximum effi-
ciency are fully considered. To make it
seem less paradoxical, it will suffice to re-
call the condition of a current employed
to produce energy under another form
than that of mechanical work, as for ex-
ample, that of the decomposition of
water in a voltameter. The number of
equivalents of water decomposed is al-
ways equal to the number of equivalents
of zinc dissolved in each of the elements
of the battery, whatever the length of
the exterior circuit, which, it must be
borne in mind, has no influence upon the
number of elements necessary to effect
this decomposition. Here, then, is a fa-

miliar experiment in which the economic
performance is not influenced by the ex-
terna] circuit."

It is very true, as M. Deprez says, that
whatever the resistance interposed be-
tween the battery and the voltameter, a
given quantity of zinc consumed corre-
sponds always to the same quantity of
water decomposed. But it happens that if
the resistance of the circuit becomes ten
times as great, the chemical actions are
effected ten times more slowly, and the
quantity of water decomposed in a given
time, as a second for example, that is to
say, the amount of energy Tu transmitted
is only one-tenth as great. But as the
quantity of zinc consumed in the same
time is also one-tenth as great, the effi-
ciency remains the same.

Faraday also proved that we may
maintain the efficiency whatever the dis-
tance of transportation, provided that
the amount of energy to be transmitted
varies inversely with the resistance.

The proposition thus enunciated (and
it is thus I think that M. Deprez intend-
ed it) is seen to be an immediate conse-
quence of our formula for efficiency (eq.
6). In effect, the electro-motive force of
the pile being constant, the efficiency de-
pends only upon the product STM of the
resistance and the energy to be trans-
mitted. This remains constant, even if
the resistance increases, provided the
work produced decreases in the same
ratio.

This proposition cannot, however, be
applied to practical uses. Suppose we
have electrical appliances capable of
transmitting ten-horse power to the dis-
tance of a kilometer, and we wish with-
out losing efficiency to transmit power to
a distance of 20 kilometers, or more ex-
actly, against a . resistance twenty times
as great. The law in question assures us
we may do it with the same apparatus,
provided that in place of ten horse power
we only transmit ££=£ horse-power; but
as ten-horse power is wanted, the prob-
lem is not solved.

Equation 6 shows that the efficiency
for a given resistance and given work
increases as the electro-motive force E.

The first thing to be determined then
with reference to electrical apparatus de-
signed for such work, is the greatest
amount of electro-motive force obtaina-
ble without injury to the insulation. This

344

VAN NOSTRAND's ENGINEERING MAGAZINE.

we will call the available electro-motive
force.

It depends — 1st, on the nature and
thickness of the insulating material em-
ployed to cover the wires of the generat-
ing and receiving machines ; and 2d, on
the nature of the insulation of the con-
ducting wire, which depends upon the
character of the supports and varies with
the climatic conditions.

This limit, as fixed by these conditions,
should be determined for any motor be-
fore commencing any important work
with it. When once the available electro-
motive force is found it should be adopt-
ed. To employ a less amount than this
thereafter, would be a lack of economy
of the same kind as using a steam-boiler
designed for ten atmospheres pressure
and never employing but two or three.

A first consequence of this important
remark is this : since the maximum elec-
tro-motive force that can be employed at
any locality is approximately determinate,
and that from the economical point of
view it should be employed for all trans-
missions great or small; it follows that
one or two kinds of machine, designed
so that with a suitable velocity this force
could be realized, could be employed for
all transmissions whatever 'their import-
ance. We will show further on how this
is possible. Such machines once in the
market, could be obtained at moderate
price.

This same remark leads us to consider
a law stated by M. Marcel Deprez in an
important paper published in La Lu-
miere Electrique, Dec. 3, 1881.

" The useful mechanical work and the
economic efficiency remain constant,
whatever the distance of transmission,
provided that the positive and negative
electro-motive forces vary as the square
root of the resistance of the circuit."

I will say in passing that if this law
merits this announcement, I believe it
proper to claim priority, as it is fairly
implied by Eq. 6, which may be found in
my communication to the Academy in
Nov. 7, 1881. It is readily seen that if
in this formula all three of the quanti-
ties E, E' and^/g vary in the same ratio,

whatever that ratio, that neither the effi-

E'
ciency — nor the useful work Tu , will
hi

change. This is the law as above stated.

Although this is very interesting from
a scientific point of view, it is unfortu-
nately of no use in practice.

Suppose we possess an electrical trans-
mission capable of transporting a certain
amount of work, Tu against a resistance
S = l and affording an efficiency of 60
per cent.; we wish to lengthen the cir-
cuit and transmit the same work against
a resistance of 25 without loss of effi-
ciency. According to the law in ques-
tion it will suffice to quintuple the elec-
tro-motive forces E and E' adopted in
the system. But if the arrangement has
been established under proper condi-
tions, we are already employing the
highest electro-motive force compatible
with the insulation of the circuit. So
that to quintuple this force, or even to
double it, is out of the question. It is
necessary to take it as it is, and to be
satisfied with a much lower efficiency in
the second case than in the first.

There are many similar laws relating
to this class of problems quite exact from
a scientific point of view, but unfortu-
nately not available for industrial pur-
poses. Perhaps the following apparent
paradox is more singular than any pre-
viously referred to :

In the electrical transmission of energy
to any amount, not only will the effi-
ciency not diminish as the distance in-
creases, but on the contrary it will in-
crease in direct proportion to the dis-
tance, so that if the latter be sufficiently
great there would be no sensible loss,
provided the electro-motive force of the
generating motor be made to increase in
proportion to the resistance of the cir-
cuit.

Suppose that E increases proportion-
ally to the resistance S, so that

I=KS,
K being an arbitrary constant,
gives for the efficiency :

Eq. 6

1 +

4T„
KS

■I m *

Then as the resistance S increases, the
efficiency also increases, although the
work transmitted TM remains constant.
And for S= infinity we have an efficiency
equal to unity.

But the difficulty of providing ade-

THE ELECTRICAL TRANSMISSION OF ENERGY.

345

quate insulation amounts to a practical
impossibility. So that, in the matter of
practical application, this last resembles
the one previously discussed.

I propose to show that the laws gov-
erning the electrical transmission of
force, supposing the currents perma-
nently established, do not differ from
those relating to transmission of force
through a simple water conduit in which
the velocity is moderate and uniform.

Suppose our store of energy at the
point A to be that of a fall of water, H
feet in height, furnishing P liters of
water per second, of wlrich we wish to
employ the least possible amount in or-
der to obtain at the point B an amount
of work=Tj,. The motor work is :

S = =— a(l — a).
J-tt

As T„ is given, we see that with a
given efficiency we can transmit against
a resistance that increases as the electro-
motive force increases. Taking for E
the maximum value E0 as before used,
then

T,„=PH

(!')•

Let the water start from a tank at A
and be delivered through a pipe or con-
duit to B, where it drives the receiving
motor. The loss of work in the con-
duit and receiving motor is at moderate
velocity sensibly proportioned to the
square of the velocity, and therefore pro-
portional also to the square of the de-
livery. The loss may then be repre-
sented by SP2, in which S is a constant
depending upon the size and nature of
the conduit and the receiving motor.

If Tu is the work afforded at B, then
the theorem of living forces gives

Tm-Tw=SP2 . . . (3')-

Finally, if H— H' is the loss of head
between A and B ; then we have

Tu =PH'

(2').

The three equations (1'), (2'), (3'j,
are identical with (1), (2), (3), with the
difference that P, H, and H' have re-
placed IE and E'. We can deduce, there-
fore, the same consequences and the
same laws.

We will now seek the solution of the
problem of electrical transmission of any
given amount of energy to any distance,
to obtain any desired efficiency without
destroying the insulation.

Let a be the efficiency to be obtained.
Eq. 6 gives :

l + |/l-

= a, . . . (a).

from which we get

Vol. XXVII.— No. 4—24.

S = ^-a(l-a).

Then for any value of a, the maximum
resistance against which work can be
transmitted is determinable, and if we
wish an efficiency very near unit}', this
resistance will become extremely small.
The problem then is this :

For a given distance of transmission,
can we, if this distance is very great, make
the resistance as small as we wish !

Now the total resistance is made up
of the resistances of the generator, the
receiver and the external circuit, which
we will express by

S=p-fp' + R.

This last term may be rendered very
small, even for great distances, by em-
ploying a large conducting wire for the
external circuit. It is only a question of
expense. There is no. impossibility in
the matter.

In regard to the resistance p of the
generator. If we reduce this resistance,
the machine will no longer furnish the
electro-motive force E0 which we require ;
and similarly if the resistance p' is made
too small, the receiving motor will no
longer furnish the electro-motive force
E'=aE0 which we require to make the

efficiency ^-=«, unless we construct ma-
hi

chines of colossal dimensions for slight

transmissions.

Of the three quantities therefore
which compose S, one only can be made
very small, and consequently the prob-
lem is not soluble, at least with such a
circuit as we have been considering.

But the problem is nevertheless capa-
ble of solution by simple means, which
I will proceed to indicate. Take near
the connections of the machine A two
points ; connect by n equal wires and
place on each a machine identical with A,
each therefore capable of producing an
electro-motive force E0.

346

VAN NOSTRAND'S ENGINEERING MAGAZINE.

In the same manner, in place of the
receiving motor, take n' receivers located
upon lines all uniting in two points upon
the principal circuit.

The intensity of the principal circuit
being I, that of each of the derived lines

will be -: the motor work expended for
n

each generator will be E-, and the total

° n

motor work remaining always

Tm=EI .... (1").

In the same manner the useful work
obtained will be

T„=ETI . . . (2")

E' being the electro-motive force of each
receiver.

Furthermore, Ohm's law applied to a
closed circuit between one of the gener-
ators and one of the receivers, will give :

E-E'=pX- + p'^+EI

n n

by making

E-E'=S'I

n n

and multiplying by I,

TTO-Ttt=ST . . . (3").

The three equations (T'j, (2"), and
(3"), differ from (1), (2), and (3), only in
the fact that S is replaced by S'. All
the consequences thus deduced with one
value of S may be realized with the other.
Terms which form S' may be made as
small as we wish; R by making the ex-
terior circuit sufficiently large, and the
other two terms by making n and n'
sufficiently great.

The problem proposed, therefore, of
transmitting any desired amount of en-
ergy to any distance and obtaining a
given efficiency, is capable of both
theoretical and practical solution.

The solution of the problem may be
effected in a more economical way by ex-
citing the separate machines upon the
derived circuits, thus reducing the num-
ber of machines, which, of course, is eas-
ily conceived.

The arrangements thus indicated by
our theory may be practically realized
and are the best we could adopt. But

the preceding theory assigns no limit to
the operation ; that is to say, according
to it, it would be really possible to trans-
mit to any distance an amount of energy
so great as to yield any desired effi-
ciency; provided we have 1st, a sufficient
number of machines, and 2d, a suffi-
ciently large conductor for the exterior
circuit.

But it is not to be expected that in
practice such a result can be completely
realized, by reason of the influence of the
extra currents due to the periodicity of
the principal currents — an influence
which we have neglected to consider, but
which becomes rapidly greater as the
length of the circuit increases. "We have
neglected, also, the currents produced in
the soft iron cores of the machines. We
reserve the discussion of these two im-
portant points.

The conclusions then are: 1st, the
problem of the transmission of a given
amount of energy to any given distance,
with a given degree of efficiency, finds no
real solution in the laws above stated.
The laws scientifically exact are illusory
in practice, because their application re-
quires either an increase without limit of
the electro-motive force, which would
render insulation impossible ; or else a
decrease indefinitely of the energy trans-
mitted, which would render the operation
useless.

2d. But the problem may be resolved
theoretically without limit; practically,
under the conditions just stated above,
by the employment of machines of or-
dinary size and uniform type for all
transmissions whether of greater or
lesser amount ; thus rendering the cost
low and the replacement easy. It will
suffice then to join a greater or less
number of these machines (for quantity
not tension) according to the work to
be performed.

3d. We can reduce the number of -the
machines in combination, described above,
by exciting directly some of the machines
in the branch circuits.

4th. It results from the above conclu-
sions there is no object gained, so far as
the transmission of force is concerned,
in the construction of colossal machines
like that, for example, which Mr. Edison
exhibited at the Exposition of 1881.
Not only will machines of ordinary di-
mensions solve the problem by the dis-

ENGINEERING NOTES.

347

position above proposed, but they have
furthermore this advantage when placed
in separate branch circuits; if one be-
comes temporarily disabled, the others
continue their work and even supply
the deficiency by an elevation of the ten-
sion.

5th. In order to establish types of
machine practically useful for all kinds
of transmission, it will be necessary to
first try some practical experiments,
easily devised, in order to determine the
maximum tension to which, in all seasons,
an aerial or a subterranean line can be
subjected.

The machines should be such as to af-
ford this tension without being driven
at too great velocities. The calculations
by which such machines would be de-
termined are analagous to those in our
communications to the Academy Nov.
14th and 21st, 1881, except for the
points mentioned below.

By the employment of such machines
under the conditions specified, we may
regard the problem of transmission to
any distance, of energy to any amount,
as solved, subject (a) to the difficulties of
the second order which may present
themselves in practice and which are al-
ways conquered ; and (b) what is more
important, the modifications to which
the results of the formulas must be sub-
jected to allow for the periodicity of the
currents, and the self-induction of the
currents among themselves ; also the
currents produced in the soft iron arma-
tures and which absorb a certain quan-
tity of work. These two phenomena,
whose effects may be quite sensible,
should cause us to regard the solutions
here given as only first approximations.
And in applying in practice any form-
ulas based on the absolute permanency
of currents, and the abstraction of cur-
rents which have their origin in iron
magnets, we ought, as in the case of re-
sistance of materials, to refrain from in-
dulging in the hope of realizing even for
a long time the extreme results which
these formulas indicate.

The discussion, however, is none the
less important and useful. It has fur-
nished us upon the essential points of
the problem of electrical transmission of
energy with some precise ideas of a gen-
eral character ; that is to say, independ-
ent of the nature of the energy trans-

mitted and of the kind of machines em-
: ployed.

It has permitted us to destroy some
erroneous ideas regarding efficiency,
, ideas which had become to some extent
convictions in the public mind. It has
! led us furthermore to the most favorable
| practical arrangements, the closest study
! of the phenomena relating to the causes
of perturbation above mentioned, modify-
ing in no essential point this disposition
of the parts, but only proving that the use-
ful effects are not as unlimited as an unrea-
soning confidence in the formulas might
lead one to believe ; formulas of first ap-
proximation only which have been the
object of this essay, and the completion
of which we reserve for the future.

REPORTS OF ENGINEERING SOCIETIES.

American Society of Civil Engineers. —
The last number of the Transactions
contains :

Paper No. 240. — On the Determination of
the Flood Discharge of Rivers and of the Back
Water caused by Contractions. By Wm. R.
Hutton. With discussions on the paper by
Theodore G. Ellis, Robert E. McMath, and t
Wm. R. Hutton.

Paper No. 241. — Accuracy of Measurement
increased by Repetition. By Stephen S. Haight.

F engineers' Club op Philadelphia. — The
j latest issue of the Proceedings coniains :

No. 3. — Applications of Logarithms to Gear-
ing. By Wiltred Lewis.

No. 4. — Working Strength of Bridge Posts.
By Geo. P. Bland.

No. 5. — Thickness of Metal for Cast Iron
Pipes. By P. H. Baermann.

No. 6. — Resistance to Traction on Roads.
By Rudolph Herring.

No. 7. — Philadelphia and Long Branch Rail-
way. By C. S. dTnvilliers.

No. 8. — Brickwork under Water Pressure.
By D. McN. Stauffer.

ENGINEERING NOTES.

rTwo distinct rock drills are used in the Arl-
L berg Tunnel. That on the east side is
the Ferroux drill, which has rendered such
good service in the St. Gothard; and that on
the west the Brandt rotary perforator, which
works by water under pressure. It has already
given good results at Pfoffensprung, and the
inventor guarantees a minimum advance of 2
meters a day, which has been considerably ex-
ceeded. The motive power is obtained by
water wheels erected in the valley which separ-
ates the two slopes of the Arlberg. The fol-
lowing figures give the progress from the com-
mencement, 17th November, 1880, to the end
of Februarv last: Advance of heading, 320

348

VAN NOSTRANIXS ENGINEERING MAGAZINE.

meters=350 yards; mean daily advance, 3.07
meters=10feet; number of blasting operations,
295; advance for each operation, 1.08 meters.=
3 feet 6 inches; number of shots in each opera-
tion, 19; weight of dynamite used for each
meter of advance, 22 kilogrammes=:say 44 lbs.
per yard.

A Massachusetts paper states that the
Railroad Commissioners have received
at their offices, in Pemberton Square, an in-
strument, by Dr. Thomson, of Philadelphia,
which is in use for the detection of color-blind-
ness upon the Pennsylvania Railroad. The
invention suggested itself to Dr. Thomson
from the fact that the number of employes
upon the Pennsylvania system of railroads
comprised upwards of 35,000 persons, scattered
over more than 2500 miles; and as the number
of trained ophthalmic surgeons was limited, it
was desirable to find a system which would en-
able the facts to be collected by any intelli-
gent employe in the company's service in
such a form as to enable decisions to be justly
made by scientific experts, although personally
absent from the examination. The instru-
ments used consist of two flat sticks, about 2
feet in length and 1 inch in width, fastened by
a hinge at one end and connected by a button
at the other. Between them, and concealed
from view, are forty white buttons, having the
figures from 1 to 40 upon them, attached to
the stick by small wire hooks, which permit of
easy removal or change of position. To the
shanks of these buttons are attached forty
skeins of colored wool. The. test skeins are
separate, and three in number — light green,
rose or purple, and red. These skeins are
shown to the persons examined in turn, and
they are directed to select from the stick the
colors which will match them. When the ex-
amination is made the instrument is closed to
conceal the number, and test greens being
shown, the person examined is directed to se-
lect ten tints from the stick ; and when this is
done the figures are recorded by the clerk, and
the selections thus made can be identified at any
future time. After a protracted experience
upon several thousand employes of the Penn-
sylvania Railroad, that company has adopted
the invention, and it will be used for examina-
tions hereafter.

RAILWAY NOTES.

A tram-car axle has been recently pat-
ented by a Dane, the object of which is
to allow the wheels to pass round sharp curves
without grinding . For this purpose the axle is
divided in the center, the end of one-half hav-
ing a hollow, and that of the other a corre-
sponding projection, somewhat similar to a
ball and socket joint, the necessary stiffness
being given to the axle by a tube which sur-
rounds the axle and extends between the naves
of the wheel, against which it bears by gun-
metal collars At the center, between the tube
and the axle is a gun-metal bearing, in which
the axle can revolve. The wheels act in such
a manner that in running along a straight line

the wheels and axle turn together, as in an
ordinary pair of wheels, but on passing round
a curve the axle slips round in its joint, so that
the wheel on the inner radius of the curve is
retarded and the outer wheel accelerated in
proportion to the sharpness of the curve,
greater smoothness being obtained in the
vehicle, and less wear and tear of the tire and
rail.

RAILROADS OF THE UNITED STATES. — Tak-
ing the whole system of which "Poor's
Manual " has information, the following com-
parisons are shown of 1881 with 1880 :

1881. 1880. Increase. P. c.

Miles of road in opera-
tion 104,813 95,455 9,358 9.8

Miles of sidings and sec-
ond track 26,211 21,978 4,233 19.2

Miles of steel tracks.... 49,063 33,680 15,383 42.7

No. of locomotives 20,116 17,949 2,167 12.1

No. of passenger cars.. 14,548 12,789 1,759 13.8

No.of baggage, mail and

express cars 4.976 4,786 190 4.0

No. freight cars 648,295 539,355 108,940 20.2

The capital and earnings of the roads report-
ing (the mileage being that of the roads report-
ing for a fiscal year to the Manual, and so not
including the road not completed till near the
close of the year) are given below :

Miles re- 1881. 1880. Increase. P. c.

porting.. 94,486 84,225 10,261 12.2

Stock and $ $ $

debt 6,010,389,579 4,879,401,997 1,112,987,582 22.7

Freigh t

earnings. 551,968,477 467,748,928 84,219,549 18.0

P £LSSGH£TGF

earnings. 173,356,642 147,653,003 25,703,639 17.4 .

Total earn-
ings 725,325,119 615,401,931 109,923,188 17.9

Expenses.. 448,671,000 360,208,495 88,462,505 24.6

ings 276,654,119 255,193,436 21,460,683 8.4

Dividends. 93,344,200 77,115,411 16,228,789 21.8

The capital, earnings, etc., per mile of road
of the railroads of the United States as report-
ed in "Poor's Manual " for eleven successive
\ ears have been :

J P.c.

Stock P. c. of of net

and Gross Ex- ex. to Net earn, on
Year. debt, earnings, penses. earn. earn, capital.

1871... 59,726 9,040 5,863 64.8 3,177 5.32

1872... 55,116 8,116 5,224 64.4 2,892 5.25

1873... 57,136 7,947 5,172 65.1 2,775 4.86

1874... 60,944 7,513 4,776 63.6 2,737 4.49

1875... 61,533 7,010 4,425 63 1 2,585 4.20

1876... 60,791 6,764 4,228 62.5 2,536 4.16

1877... 61,650 6,382 4,075 63.8 2,307 3.74

1878... 59,040 6,232 3,847 61.7 2,385 4.04

1879... 58,070 6,244 3,670 58.8 2,610 4.49

1880... 60,050 7,307 4,277 58.5 3,030 5.00

1881... 63,611 7,677 4,749 61.9 2,928 4.60

Gro-s earnings, we see, fell off every vear^
from 1871 till 1878, and have risen since lv-per*
cent, from 1879 to 1880, and 5 per cent, from
1880 to 1881 . Expenses decreased yearly from
1871 to 1879 — one year longer than earnings —
but have advanced in the last two years nearly
as much as they had fallen in the previous
five years. Net earnings have varied much
less than gross earnings ; but they fell from
1871 to 1877, and then rose for two years, but
fell off last year again, remaining larger, how-
ever, than in any previous years, except 1871
and 1880. Of the proportion of net earnings
to capital, we have already spoken. — Railroad
Gazette.

IRON AND STEEL NOTES.

349

THE extent to which the manufacture of
locomotives is now carried on in the
United States may be gathered from the figures

given below, which we take from Mr. Drum-
mond'> report. There are now 15 locomotive
works in the United States, with a capacity of
from 8 to 50 engines per month. In 1881 they
turned out in round numbers 2,700 locomotives.
Add to this 300 built by railway companies.
and we have at least 8,000 new engines con-
structed (luring the year, besides those rebuilt.
At the commencement of last year there were,
speaking roughly. 18.000 locomotives running
on the 94,000 miles of railway in the Union, or
an average of about one engine to every five
miles. If, as is probable, the new railway con-
struct ion this year reaches 10,000 miles, this
average would call for 2,000 new engines. The
life of a locomotive is estimated by manu-
facturers to average from fifteen to twenty
years. The latter figure is probably more
nearly correct, as the improved condition of
American railways has prolonged the existence
of engines considerably. At this rate about
1,000 new engines per year would be required
to keep good the reduction by decay. Adding
this to the 2,000 presumably required this year
for the increased mileage, we find that about
3,000 new engines will be demanded. The
great Eoston statistician, Mr. Atkinson, be-
lieves that in the next sixteen years there will
be added 100,000 miles of rail. They deal in
big figures over the water. — Engineer.

ORDNANCE AND NAVAL.

The New German Magazine Gun. — This
weapon, which is considered by the Ger-
man Government to have proved itself the most
suitable military repeating rifle, is the invention
of Messrs. Mauser, the originators of the pres-
ent German regulation rifle. The magazine
consists of a tube contained in the stock, and
has a spiral spring which keeps the cartridges
up to the breech action. When the bolt is
withdrawn, a cartridge — which has been forced
out of the magazine by the spiral spring — is
raised up to the level of the cartridge chamber,
into whi'-h it is driven by the bolt as it returns.
The whole action of loading is comprised in
the backward and forward motion of the bolt.
In order to avoid waste of ammunition, a lever
is attached to one side of the action, by which
the magazine can be instantly closed, the gun
being then loaded and fired as an ordinary
breechloader. The reloading of the magazine
i- -tated only to occupy a few seconds. This
system can be applied to the Mauser rifles of
1871 model now in use, at very small cost.
Two thousand of these weapons are in the
course of construction, and will be served out
quickly as possible to one of the grenadier
regiments now quartered in Spandau.

IRON AND STEEL NOTES.

F"pwo inventors in Bohemia have patented

_L a process for enameling cast iron water

pipes, which can be applied to other hollow

castings that are made with cores. It consists, I

the Building Ni IM says, in simply covering the
sand core with the enamel and then pouring in
the iron as usual. The heat of the melted iron
fuses the enamel, which attaches itself firmly
to the iron, and detaches itself so completely
from the sand that the enamel is said to be all
that can be desired for water pipes and other
industrial purposes. In casting sinks, basins,
urinals, &c, the enamel can be applied to the
sand on that side of the mould which is to form
the inside of the basin. The composition of
the new enamel is kept a secret, but is said to
differ from the old form in the simplicity of its
preparation and the extraordinary cheapness of
the materials used. In color this new enamel is
gray. It will be useful for gas pipes, and soil
pipes as well as water pipes, because it will
make the pipes absolutely tight by a glassy
lining.

Painting Ikon Surfaces. — Continually
growing in importance as iron becomes
more and more an every-day building material
is the best method of preserving it by paint,
The various chemical methods of rust-preven-
tion being as yet too imperfect and too expen-
sive for ordinary use. The following extracts
from a paper read by Mr. William Meeking,
before the Civil and Mechanical Engineers' So-
ciety, London, furnishes some technical points
of interest in relation to this subject. It says :
Of the varieties of lacquers and paints used
it is needless to speak at length as the all im-
portant point is the actual state of the iron sur-
face when the first coat is laid on. If that is
not in proper condition no subsequent applica-
tion, however good in itself, has any chance of
being permanently preservative, and I think
that that proper slate is found when there has
been formed upon the whole surface of the
work a thin layer of the first or black oxide,
which has been, while hot, :horoughly perme-
ated by and incorporated with a resinous and
tarry covering. Once formed, everything goes
well. Additional coats of paint may be ap-
plied from time to time to renew the thickness
of the original covering, but the iron under-
neath remaius unattacked. If, on the contrary,
a film of hydrate oxide (ordinary rust from ex-
posure) be once allowed to form, the successive
coats of paint are thrown off sooner or later,
and, in the meantime, the rust has spread under
the paint. A striking instance of this may be
generally seen after outdoor riveted work has
been in place for some time. As a rule all the
riveting is done before the final painting is com-
menced, and each rivet-head has in the mean
time been exposed to a damp atmosphere ; the
paint invariably commences to peel off the rivet
heads long before it leaves the adjacent plates,
and when this has once taken place nothing but
a thorough scraping off of the surface will give
the paint any chance of adhering. So slight
are the differences of manipulation which de-
termine whether a given piece of work shall or
shall not rust away, that I think they may all
be found in the different methods of manufac-
ture pursued now and formerly. Taking the
case of a piece of ornamental iron work, which
in so many instances has come down to us in
unimpaired beauty and condition, it would be

350

VAN NOSTRAND'S ENGINEERING MAGAZINE.

now probably forged in detail in one part of a
factory, drilled, filed and fitted in another, and
when completely finished be painted ' ' in three
coats of best oil paiDt." Formerly the smith
who forged the work punched the necessary
holes at the same time, fitted his various pieces
together as he went on, completing each piece
as he proceeded, doiDg all the work with his
hammer, and, to quote an old book of direction
to good smiths, " brushing his work over with
linseed oil, and suspending it for some time
over a strongly smoking wood fire." This will
give at once a sort of elastic enamel coat, per-
fectly adherent, calculated to preserve the iron
to the utmost.

To come to practical uses : it appears to me,
first, that in all cases where iron is u-ed exter-
nally there should be the most careful provision
made for draining ofl! water, and preventing
any lodgment in inaccessible places ; second,
that the iron used should be in the largest and
most compact masses possible, wiih a due re-
gard to the necessities of construction, avoid-
ing, by all means, such designs as are calcu-
lated to provide the largest possible surface for
a given weight of metal ; third, to take care
that, before the metal leaves the iron work«,
and while heated, it receives a coat of some pro-
tective substance, such as tar or linseed oil,
which shall be allowed to incorporate itself
with its external surface and form a durable
substratum for future ccverings.

BOOK NOTICES.
publications received.

r) eport of the board of commissioners
\j of the Ninth Cincinnati Industrial
Exposition.

Report of New York State Survey
for the Year 1880. James T. Gardner,
Director.

Constitution, By-Laws and List of Mem-
bers of the American Society of Civil
Engineers.

Astronomy Corrected. By H. B. Phil-
brook. New York : J. Polhemus.

"Oefining and Separating the Metals
JL\ Constituting Base Bullion by the
Electrolytic Process. By N. S. Keith.

Monthly Weather Report for July.
, Washington : Government Printing Of-
fice.

Modern Applications of Electeicity.
By E. Hospitalier. Translated by Julius
Maier, Ph. I). New York : D. Appleton & Co.
Price $4.50.

Five years ago, as the translator of this book
says, " a work like the present would have had
no raison d'etre ; at this moment it requires no
introduction and no recommendation."

What the reader chiefly desires to know is :
how completely does it fulfill the implied
promise of the title ? To which it may be
answered, that the original treatise was com-
pleted last year by an unquestioned authority

in electrical science, and who had enjoyed ex-
ceptional advantages for gathering the neces-
sary information.

In addition to which it should be said that the
translator carefully compiled and added an ac-
count of the discoveries in practical electrical
science made during the year which has in
tervened, only completing his work in April
last.

456 pages of text are illustrated by 170 good
wood-cuts.

The non technical reader can understand it
all.

Olmstead's College Philosophy. Third
Revision, by Rodney G. Kimball, A.M.
New York : Collins & Brother.

For many years Olmstead's Philosophy has
held a deservedly high place among American
text-books. The successive editions have been
revised by able writers, who have incorpo-
rated in their work the later discoveries, so that
notwithstanding an increasing number of com-
petitors, the book is still considered by promi-
nent instructors as the best compend of the
fundamental principles of physical science, and
moreover, the book best fitted for the purposes
of instruction.

Many teachers and students throughout the
country will gladly learn that the book will in
nowise lose prestige by this last revision. With
a full appreciation of the merits which had
previously insured success, and with the talents
of a successful teacher of applied science,
Prof. Kimball has brought this favorite text-
book abreast with modern science, and made
it again a sufficient course of Physics for high
schools and colleges.

The new edition is necessarily somewhat
larger than the previous one. New sections
and new illustrations were indispensable. The
concise, logical and accurate method of pre-
senting the principle characterizes the new por-
tion as it did the old.

Continuous Railway Brakes. By Michael
Reynolds, London: Crosby, Lockwood &
Co.

The author's preface says, "I have endeav-
ored to explain from my experience what a con-
tinuous brake should be capable of doing, and
when it is found most useful.

" I have given cases to show that a continu-
ous brake in the hands of the driver would,
in all probability, have saved the lives of pas-
sengers who were killed. With such evidence
before us, every accident which takes place in
the future with fatal results will, no doubt-, be
subjected to rigorous investigation. * * *

" I have endeavored to illustrate continuous
brakes for the ordinary reader, at the same
time adhering closely to technical details of
construction for the professional reader."

The brakes illustrated and described at length
are the screw brake, chain brake, Smith's vacu-
um brake, Hardy's vacuum brake, Steel &
Mclnnes' compressed-air brake, Earned contin-
uous vacuum brake, Aspinwall's automatic
vacuum brake, Barker's hyTdraulic continuous
brake, Sanders' vacuum brake, and the West-
inghouse automatic brake.

MISCELLANEOUS.

351

L'ELECTRICITIE ET 8E8 Applig
Henri de Parville, Paris: (». M-

i CATIONS. —
[asson.

This is a popular ami well illustrated account
of the Paris Electrical Exhibition.

Beginning with a discussion of the nature of
electricity, the author passes quite directly to
the methods by which it i> produced. Then
comes the transmission of energy, electric light-
ing, telephones aud microphones; the latter es-
pecially receiving an undue share of attention.

The illustrations which are good and abun-
dant will look familiar to readers who have
read the current literature on applications of
electricity.

rpiiE Metal Turner's Hand-book. By
J_ Paul N. Has buck, London: Crosby,

Lockwood & Co. Price, 40 cents.

This useful ltttle treatise is designed for ama-
teur workers at the foot lathe.

Lathes are treated first, then gearing attach-
ments, slide rests, chucks, cutters, tool grinding
and finally lathe motors.

The author wastes no words in his descrip-
tions. The illustrations are very numerous,
there being one hundred figures for one hun-
dred and fifty pages of text.

Any one owning a foot lathe will find this
little book worth the price demanded for it.

ryiHE Laboratory Guide : A Manual of
J. Practical Chemistry, for Colleges
and Schools, Specially Arranged for
Agricultural Students. By Arthur Her-
bert Church, M. A., of Lincoln College, Oxford.
Fifth edition, revised and enlarged. London:
John Van Voorst.

On comparing the present edition of Prof.
Church's Laboratory Guide with its earlier
phases, we cannot fail to be struck with the
great changes which have been made. Whilst
the general plan of the work has been retained,
and whilst none of the features which won for
it the general approval of teachers and students
have been sacrificed, additions and improve-
ments have been numerous.

The chapter on the analysis of drinking-
water has been greatly enlarged and modified.
It is very satisfactory that Prof. Church does
not consider that the character of a water can
be deduced from two or three data alone, but
considers it advisable to ascertain the presence
or absence of phosphoric acid, to observe the
action of the water on lead, to apply Heisch's
sugar-test, and to submit the deposit to micro-
scopic examination. He does not refer to the
presence or absence of free oxygen, which is
in some cases an important feature.

The instructions for the determination of the
albumenoids in articles of diet, form an exceed-
ingly useful addition in the present volume as
compared with the earlier editions. Until a com-
paratively short time ago it was believed that
the nutritive value of any root, leaf, &c, could
be discovered by a simple determination of its
total nitrogen. It is now known that nitrogen
can and does exist in forms in which it is not
capable of assimilation by the animal system.
Hence a determination of the albumenoids be-
comes necessary. Two methods for this pur-
pose with carbolic acid and with copper hy-
drate are accordingly given.

Prof. Church's work as it stands is undoubt-
edly the best laboratory guide which can In-
put into thehandsof the agricultural student, —
a class whose requirements extend far beyond
that mere valuation of manures and soils of
winch they are popularly supposed to consist. —
Chemical Review.

MISCELLANEOUS.

A New Electro-Dynamometer.— At the
meeting of the Physical Society of
London, which was recently held at the Clar-
endon Laboratory, Oxford, an electro-dyna-
mometer, which has some novel points of con-
struction, was exhibited by Dr. W. H. Stone,
F.R.S. It was designed for measuring the
currents used in the medical applications of
electricity, and originated in a suggestion of
Mr. W. H. Preece, made at the Society of
Telegraph Engineers, when Dr. Stone read a
paper on "Medical Electricity," which we re-
ferred to in a recent note. The chief novelty
in the new instrument is the use of aluminium
wire instead of copper for the suspended coil.
Aluminium is chosen because of its lightness
as compared to copper, and its equal conduc-
tivity to copper, weight for weight. In an
electro-dynamometer the movable coil ought to
be as light as possible, other things being the
same, as it plays the part of a needle and is de-
flected by the current just as the aluminium
needle of a quadrant electrometer is deflected
by the difference of potentials between the
quadrants. The aluminium coil of Dr. Stone
was made from silk-covered wire prepared by
Messrs Johnson and Matthey, and is wound
into without a frame, the convolutions being
bound together by small ties of silk and
a lacquer of amber varnish such as is used by
photographers. Dr. Stone recommends this
varnish for delicaie electrical uses instead of
the ordinary shell-Ian varnish. The coil is
suspended from two fibers of silver gilt wire,
such as is used in gold-lace making. This wire
is gilt before it is drawn, and has a high con
ductivity. Thus a meter of wire ^ff in. in
diameter measures 9.8 ohms, whereas a plati-
num wire of the same length and thickness
measures 62.2 ohms. As the current is con-
veyed to the suspended coil by this wire, it is
important to have it of low resistance. More-
over, the gilt surface makes a good clean con-
tact with the aluminium wire of the coil, and
thus overcomes one of the leading obstacles in
the way of using aluminium wire for electrical
purposes. Dr. Siemens and others have tried
to use aluminium before, but the difficulty of
getting a good soldered joint was found to be a
drawback. The gold and aluminium clamped
together or soldered after the aluminium is
electro-plated with a solder-holding metal, is
likely, however, to answer the purpose. Alu-
minium has also a high specific heat, and is
very difficult to fuse, therefore it is adaptable
for resistance coils. The bifilar suspension is
necessary in Dr. Stone's instrument to give the
coil a directive force and bring it back to zero.
The silver-gilt wires are hung from two brass
springs placed horizontally and opposite each

352

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

other. These springs can be drawn apart if
need be by means of adjusting screws in order
to vary the sensitiveness of the needle. The
instrument is small in size, and of a portable
construe tion. — Engineering.

Professor H. M. Paul has communicated
to the Seismological Society of Japan
some notes on the effect of railway trains in
transmitting vibrations through the ground.
A box, holding about 20 lbs. of mercury thick-
ened by amalgamation with tin, was placed
upon a heavy plank screwed to the top of a
post sunk 43*£ ft. into the ground. Images re-
flected in the surface of the mercury were ob-
served by a telescope, as in meridian observa-
tions. An express train passing at a distance
of one-third of a mile, set the surface of the
mercury in confused vibration for two or
three minutes. The experimenter, Nature
says, also found that a one-horse vehicle pass-
ing along a graveled road 400 ft. or 500 ft. dis-
tant caused a temporal agitation of the mer-
cury whenever the wheels struck a small stone.

Instead of the methods of testing and com-
paring hardness at present in use, Dr.
Herz, of Berlin, has sought a more absolute
method, and he has confined himself, on ac-
count of the complexity of the question, to
the consideration of isotropic elastic sub-
stances. In tbese the hardness may be de-
termined by the pressure which must be ex-
erted on a rouDd mass to exceed the limit of
elastic resistance. In the case of plate-glass,
e.g., it was found by experiment that, at a
pressure of 136 kilogramme* per square mil-
limeter, the limit was passed, and a circular
crack was produced; 136, accordingly, ex-
presses the degree of hardness of the glass. Every
isotropic body which has its limit of elasticity
exceeded under greater or less pressure is, re-
spects ely, harder or less hard. The advan-
tage of this method lies in the fact that no sec-
ond substance is needed, but only two speci-
mens of the substance examined.

A small international industrial exhibition
is being held at Lille, under the auspices
of the municipal authorities. The exhibitors,
are chiefly French and Belgian, but there are
two English, viz., Doulton and Minton, cer-
amic ware being one of the classes. A promi-
nent feature is the artistic ironwork, produced
entirely by the hammer, and black, relieved
by polished steel, nickel, and copper, which
produce an excellent effect; fine scroll-work,
flowers, and fruit are marvelously executed.
One of the Dandenne perpetual clocks, like
that at the Northern Terminus, Brussels, is
erected outside the building. It is kept going
by the weights being kept constantly wound
up by a fan actuated by the ascensional cur-
rent of an air tight shaft ; and when the weight
nears the top of its course it puts on a brake
which stops the fan, provision being made for
twenty-four hours' working in the event of a
temporary cessation of the current. Some
original improvements in mechanical drawing
appliances are shown by M. Jardez, of Lille.
He stretches the paper by a panel secured by
iron bars. The left-hand edge of the board is

provided with a scale and also with a grooved
rod, fixed by pins, on which the square works
for dispensing with a true edge. The stock
of the T-square has an aperture for adjustment,
and the blade is also graduated. There is be-
sides a small rack for hatching regularly.
Other noveliies are folding iron trestles and
some metallized cloth for roofing purposes. —
Engineer.

At a meeting of the Cleveland Institution
of Engineers, held at Middlesbrough
on Monday evening, the 12th inst., Mr. J. E.
Stead, F.C.S., read a paper "On the Rapid
method of Estimating Phosphorus." He de-
scribed the old method of testing for phos-
phorus, which occupied two days for each
estimation. He then explained the new plan
he had devised, whereby the same results can
be obtained in two hours. In testing for phos-
phorus in basic steel, there is a special advan-
tage in dealing with such material, because it
contains no silicon, and under such circum-
stances the phosphorus can be determined in a
single hour. The principal saving of time
arises from the absence* of any necessity for
artificial drying. Mr. Stead then read another
paper upon a new apparatus designed by him-
self for analyzing blast furnace gases. The ap-
paratus is in two portions — one portion being
used for collecting samples of gas from the
mains, and the other portion for dealing with
it in the laboratorj^. Mr. Stead stated that
during the production of one ton of pig iron
combustible gases weighing nearly 7 tons pass
off from a Cleveland blast furnace, and that
the calorific power of these gases is equal to
that furnished by the combustion of 11^ cwt.
of coal. In the production of one ton of pig
iron. 5| tons of air are forced into the furnace,
and the combustible gases drawn off from the
top of the furnace require 4f tons more air to
complete their combustion. The total final
products of combustion weigh llf tons, and
these pass into the atmosphere as waste gases.
Mr. Stead advocated strongly the systematic
examination of blast furnace gas, stating that
he had occasionally detected that one-third of
the combustible gas produced was passing
into the atmosphere unconsumed. This was
equivalent to throwing away about 70 tons of
coal per week for each furnace producing.400
tons per week of pig iron. — Engineer.

Anew explosive has been invented by M.
Petri, a Viennese engineer. The name
given to it is dynamogen, and, according to
the Neue Militarische Blatter, it is likely te com-
pete seriously with gunpowder. The inventor
states that it contains neither sulphuric acid,
nitric acid, nor nitro-glycerine. The charge of
dynamogen is in the form of a solid cylinder,
which can be increased in quantity without be-
ing increased in size, by compression. The
rebound of the guns with which the new ex-
plosive has been tried is said to have been very
slight. It is also said that the manufacture of
dynamogen is simple and without danger, that
it preserves its qualities in the coldest or
hottest weather, and that it can be made at 40
per cent, less cost than gun powder.

VAN NOSTEAND'S

Engineering Magazine.

NO. CLXVII.-NOVEMBER, 1882 -VOL. XXVII.

THE THEORY OF THE GAS ENGINE.

By DUGALD CLERK.
From Proceedings of the Institution of Civil Engineers.

The practical problem of the conver- j
sion of heat into mechanical work has |
long occupied the minds of engineers |
and scientists ; the steam engine is a
partial solution, but although perfect as
a machine, its efficiency is so low that it
can hardly be considered as satisfactory
and final. As the result of the best
modern practice it may be taken that the
steam engine does not convert more than
10 per cent, of the heat used by it into
work, and this in engines of considerable
size and with boilers and furnaces fairly
efficient. In small engines it is much
less, indeed it is certain that few among
the thousands of steam engines in daily
use below 6 HP. give an efficiency greater
than 4 per cent. The great cause of loss
is the amount of heat necessary to change
the water from the liquid to the gaseous i
state, most of this heat being rejected
with the exhaust either into the conden-
ser or the atmosphere. Many attempts
have been made to use liquids of lower
specific heat than water, and requiring
less heat for evaporation, the principal
being alcohol, ether and carbon bisul-
phide, but for obvious reasons no success
has been attained.

To heated air as a means of obtaining
power, the objection of loss by latent
Vol. XXVII.— No. 5—25.

heat does not apply, the air is already in
the gaseous statej and any heat added at
constant volume increases the tempera-
ture, and therefore the pressure, without
the complication of change of physical
state. A high efficiency would therefore
be expected, and according to Professor
Rankine the efficiency of the fluid in the
engines of the " Ericsson " was about
0.26 ; the efficiency of the furnace was
however low. and accordingly the actual
efficiency oc the engine was no higher
than that of the best steam engines now
in use. In the " Stirling" hot-air engine,
he found the efficiency of the fluid to be
0.3 with a higher efficiency of furnace
than in Ericsson's.

In the Ericsson engine the air was
heated at constant pressure, the volume
augmenting and the power being given
by the increased volume of the air as it
entered the motor cylinder from the re-
servoir into which it had been compress-
ed. The mean effective pressure was
only 2.12 lbs. on the square inch ; the
size and friction of the engine for a given
power was enormous. In the Stirling
engine the air was heated at constant
volume with increase in pressure, the
power being obtained by subsequent ex-
pansion ; the mean available pressure

354

VAN NOSTRAND'S ENGINEERING MAGAZINE.

was 37 lbs. per square inch, and the fric-
tion of the engine only amounted to one-
tenth of the total indicated power. Both
engines used the now well known contri-
vance, the regenerator, which was the
invention of Dr. Stirling, and which is
the cause in both of the high efficiency.

The failure of these engines was due
to the rapid burning out of the cylinder
bottoms by the direct action of the fire,
it being found impossible to heat the air
rapidly enough to the required tempera-
ture without maintaining the temperature
of the metal surfaces much higher than
the maximum temperature to be attained
by the air. To overcome this slow heat-
ing of the air when in mass has been the
object of many inventors, and a type has
often been proposed with a closed fur-
nace, and the air forced through this
furnace keeping up the combustion, the
hot products going to the motor cylinder
and there doing work. This method of
internal heating, however, introduces dif-
ficulties as grave as exist in the external
method. The hot gases having to pass
through pipes and valves to the motor
cylinder renders it impossible to main-
tain a very high temperature without
damage to the machine. # Sir George
Cayley was the first to make and work
experimentally an engine of this type.

In view of these futile attempts, until
very recently hot air was considered as
among the failures of the past, and it
was believed that, imperfect as the steam
engine is, nothing was likely to succeed
in producing a better result.

The great progress made in recent
years with the gas engine, and its advance
from the state of an interesting but
troublesome toy to a practical powerful
rival of the steam engine, has shown that
air may after all be the chief motive
power of the future. In the gas engine
chemical considerations greatly modify
the theory and prevent it from ranking
as a simple hot-air engine; but to be
thoroughly understood it is better first
to consider the power to be obtained
from air under certain theoretical condi-
tions.

Three well defined types of engines
have been proposed —

(1.) An engine drawing into its cylin-
der gas and air at atmospheric pressure
for a portion of its stroke, cutting off
communication with the outer atmos-

phere, and immediately igniting the mix-
ture, the piston being pushed forward
by the pressure of the ignited gases
during the remainder of its stroke. The
in-stroke then discharges the products
of combustion.

(2.) An engine in which a mixture of
gas and air is drawn into a pump, and
is discharged by the return stroke into
a reservoir in a state of compression.
From the reservoir the mixture enters
into a cylinder, being ignited as it en-
ters, without rise in pressure, but simply
increased in volume, and following the
piston as it moves forward, the return
stroke discharges the products of com-
bustion.

(3.) An engine in which a mixture of
gas and air is compressed or introduced
under compression into a cylinder, or
space at the end of a cylinder, and then
ignited while the volume remains con-
stant and the pressure rises. Under this
pressure the piston moves forward, and
the return stroke discharges the exhaust.

Several minor types have been pro-
posed, and many modifications of these
three methods are used. A thorough
understanding of these, however, renders
it possible to judge the merits of any
other.

Types 1 and 3 are explosion engines,
the volume of the mixture remaining
constant while the pressure increases.
Type 2 is a gradual combustion engine
in which the pressure is constant but
the volume increases.

The author, in the course of his ex-
periments on gas engines, has found that
13537° Centigrade is the temperature
usually attained by the ignited gases in
his engine, and he has accordingly in-
vestigated the behaviour of air under
different conditions at this temperature.

Type 1. Suppose an engine to have a
piston with an area of 144 square inches
and a stroke of 2 feet. Let the piston
move through the first half of its stroke
drawing into the cylinder air ; let enough
heat be immediately added to this air to
cause it to rise instantly to 1,537° Centi-
grade, and the piston continue moving
forward under the pressure produced. If
there be no loss of heat through the sides
of the cold cylinder, but the temperature
of the air fall only through performing
work, how much work would be done
when the piston completes its out-strokeu?

THE THEORY OF THE GAS ENGINE.

355

The air before the heat is added is
supposed to be at a temperature of 17 c
Centigrade (about 00° Fahrenheit), and
the ordinary atmospheric pressure. In
Fig. 1 the line marked adiabatic No. 2 is
the curve showing the work which would
be obtained under the supposed condi-

Mean pressure during available part ) on u ,. _
of stroke ^8».81DB.

Temperature of air at the end of/ ., nQQ°n
stroke f l»ww U'

Work done on piston 5,781 loot lbs.

5 731
Duty of engine 2^^3=0.S1.

Fig.1.

900
BO
M
70

*o
50

100

so
70
80
SO
40
90

100
.90
»
70

—

p20

fe,

^ X

. > ^

><c

\217.5

t5>

X; /. ..

1% Pfc

VSI.M

v..

GO
30
40
30

'>!

3.C

>cJ

-.9

!2~—

^£^7

W.2-

j—

—

~~~

—

— ■

j '

I I.I M I

1 i 1

1 CUBIC foot.

135 7.0
I089.O
648C

2 cubic feet.

tions. Fig. 2. is the indicator diagram
such an engine would furnish. It is not
necessary here to detail the calculations.
With this paper is given a table of the
data used, so that the numbers may be
verified. The following are the results :

As the engine is supposed to draw in

air for half of its stroke, the last half of

the stroke only is utilized for power ; the

mean available pressure calculated for

39 8
the whole stroke is only— ^- = 19.9 lbs.

Fig-

250

-C

£200
o

«150

£100

</>

£ 50

15 37

I7°C

)

I i

> 1

5 1

\ 1

0
cubi

L
: foo

2c»

\) 1
jbic '

ioso°c Atmo-
. sphere

Boa

1 cubic foot of air (at 170° Centigrade,
and 760 millimetres mercury) re-
maining at constant volume re-
quires to heat it to 1,537° Centi-
grade, an amount of heat equiva-
lent to

Maximum pressure in lbs. per square
inch above atmosphere

Pressure at the end of stroke per
square inch above atmosphere. . . .

26,762
* foot-lbs.

76.6 *bs.
19.6 lbs.

per square inch. There is a considerable
pressure at the end of the stroke which
could be made to give more work by ex-
panding further ; but for the purpose of
comparison it is better to consider the
three types of engine as each having a
cylinder capacity swept by the piston of
2 cubic feet, and in each case using in its

356

VAN NOSTKAND'S ENGINEERING MAGAZINE.

operation 1 cubic foot of air at each
stroke.

Type 2. Suppose an engine to draw
into a pump 1 cubic foot of air, on its
return stroke forcing the air into a reser-
voir at a pressure of 76.6 Jbs. per square
inch above the atmosphere. The motor
piston is now at the beginning of its out-
stroke, and as it moves forward air from
the reservoir enters the cylinder, but as
it enters it is heated to 1,537° Centigrade,
without rise in pressure ; the motor pis-
ton sweeps through 2 cubic feet.

Fig. 3 shows the indicated card of this
engine. abed is the pump diagram.
Air at 17° Centigrade is taken in, com-
pressed without loss of heat, the temper-
ature rising under the compression to
21 7°. 5 Centigrade. When it is equal to

1 cubic foot of air (17° Centigrade^
and 760 millimeters mercury) at |
constant pressure requires to heat ! 32,723
it from the temperature of com- ( foot-lbs.
pression217°.5 to l,537°Centigrade |
heat equivalent to J

Maximum pressure in lbs. per square \^aa iv^
inch above atmosphere ) ' '

Pressure at end of stroke above at- ) 1Q P ,,
mosphere J" iyo 1DS'

Mean pressure during available ) 47.1 lbs. per
part of stroke [ square inch.

Temperature of air at the end of ) 1,089°
stroke \ Centigrade

Work done on piston 11,759 foot-lbs.

Duty of engine ^i^=0.S6.

Type 3. Suppose an engine to draw
into a pump 1 cubic foot of air, on its
return stroke forcing it into a reservoir
at a pressure of 40 lbs. above the atmos-
phere. The motor piston is now at the

Fig.3

250
200
150

100

I537°C

50
0

^~r—~ - — L.. i .

^""~-~

^B^^I^SK

__!____

I L~1

I ]

L- 5

> i

!
1

) "1

cub

0 ]

ic fo

crt

! i

t •

> <

J
cubi

) 1
: fee

Atmo-
089 c sphere
line.

the pressure in the reservoir it is forced
into the reservoir, as is shown on the
line b e.

In all the operations no loss or gain of
heat is assumed, except in doing work or
in work being done on the air. In the
motor diagram from c to e the air is flow-
ing from the reservoir following the pis-
ton, and the temperature is 1,537° Centi-
grade during the whole admission. At e
the communication with the reservoir is
cut off, and the temperature falls while
the air is expanding doing work, until it
reaches the end of the stroke, when the
exhaust is discharged by the return
stroke of the piston.

For convenience the pump diagram is
shown on the motor one, and the shaded
portion represents the work done by the
air as the result of the cycle. As the
heat is added while the air expands in
volume, it takes considerably more to
raise a cubic foot of air to the required
temperature than in the case of type 1.

beginning of its out-stroke, and as] it
moves forward air from the reservoir
enters the cylinder while the piston
sweeps through 0.39 cubic feet. At this
point communication is cut off, and the
temperature suddenly raised to 1,537°
Centigrade. Hitherto the air has re-
mained at the temperature of compres-
sion 150°. 5. The pressure goes straight
up ko 220 lbs. above the atmosphere.
This is shown at Fig. 1, and also at Fig.
4, which is the diagram of this type of
engine, a b c d is the compression dia-
gram ; a b ef the motor diagram. ^The
piston continues to move forward, and
the air expands doing work. At the end
of the stroke the pressure has fallen to
8.4 lbs. per square inch above the atmos-
phere.

1 cubic foot of sir (17° Centigrade, ""
and 760 millimeters mercury) at
constant volume requires to heat it ! 24,416
from the temperature of compres- | foot-lbs.
sion 150°. 5 Centigrade to 1,537°
Centigrade heat, equivalent to

THE THEORY OF THE GAS ENGINE.

357

Maximum pressure in lbs. per square ) OO0 ,.

inch above atmosphere )

Pressure at end of stroke 8.4 lbs.

Mean pressure during available ) 47. S lbs. per

part of stroke f square inch.

Temperature at middle of stroke [- c'enti^ratlo.
Temperature at end of stroke.. .648 Centigrade
Work done on the piston. . 11,090 foot-lbs

Duty of engine -— — — ,=0.45.
* 24,416

The relative work obtained from 1
cubic foot of air heated to the assumed
temperature is shown below.

results FROM km. inks OF EQUAL VOLUME

SWEPT BY MOTOK 1MSTON.
Type

1. 5,781 foot-lbs. work obtained 0.21 duty.

2. 11,769 " " " 0 30 •'

3. 11,090 " " " 0.45 "

Fig.4

9 10" 1

1 cubic foot.

8 9 10
2 cubic feet

Atmo-
sphere
line.

Fig. 5 shows the most important modi-
fication of this type ; in it, instead of a
separate reservoir, a space is left at the
end of the cylinder, into which the piston
does not enter, and in this, space is com
pressed the gases forming the inflamma-
ble mixture. The rise in pressure there-
fore commences at the beginning of the
stroke instead of when the piston has

That is, in an engine of type 1, if 100
heat-units be used, 21 units will be con
verted into mechanical work. In type 2,
with the same amount of heat, 36 units
will be given as work, and in type 3 no
less than 45 units would be converted
into work.

The great advantage of compression
over no compression is clearly seen, by

Fig.5

£50

c200

150

o .

1^50
Sc

£ o

I537C

■

^_J_

0 1

■

! H

> (

0 1

: i

PARTS OF THE STBOKE.

traveled out. In this diagram the volume
swept by the piston and the clearance
space together are supposed to be equal
to 2 cubic feet. Comparing the results
obtained from these three modes under
precisely similar conditions, the same
weight of air heated to the same degree,
and used in cylinders of identical capa-
city, there is a considerable difference in
the results possible even under the
purely theoretic conditions stated.

the simple operation of compressing be-
fore heating ; the last type of engine
gives for the same expenditure of heat
2.1 times as much work as the first.
Compression, as used by the second
type, does not afford so favorable a re-
sult ; but even then the advantage is
apparent, 1.6 times the effect being pro-
duced. By a greater degree of compres-
sion before heating even better results
are possible. In an engine of type 3

858

VAN NOSTRAND's ENGINEERING MAGAZINE.

expanding to the same volume after igni-
tion as before compression, the possible
duty D is determined by the atmospheric
absolute temperature T', and the abso-
lute temperature after compression T; it is

T— T'

D= — =— whatever may be the maxi-
mum temperature after ignition. In-
creasing the temperature of ignition in-
creases the power of the engine, but
does not cause the conversion of a
greater proportion of heat into work.
With any given maximum temperature
the smaller the difference between that
temperature and the temperature of
compression, the greater is the propor-
tion of added heat converted into work
with any given amount of expansion.
The greater the compression before igni-
tion, the more closely the two tempera-
tures come together, and the higher is
the duty of the engine ; neglecting in the
meantime the practical conditions of loss.
What compression does is to enable a
great fall of temperature to be obtained
due to work done with but a small move-
ment of the piston. In type 1 when the
piston has reached the end of its stroke,
the increase from the moment of ignition
is only from one volume to two volumes,
while in type 3 with the same total
volume swept by the piston, it increases
from one volume to five volumes. In
the one case the ratio of expansion is
two, while in the other it is five. This
will be readily seen in Figs. 2 and 4.
Now this increased expansion is not ob-
tained at the cost of loss average press-
ure ; in type 1 the mean available press-
ure over the whole stroke is nearly 20
lbs. per square inch, while in type 3 it is
38.5 lbs. per square inch ; that is, the
compression engine for equal size and
piston speed has nearly twice the power
of the other.

In the compression engine with a
maximum temperature of 1,537° Centi-
grade, the final temperature is 648°
Centigrade, while in the other, with the
same maximum temperature, the final
temperature is 1,089° Centigrade. It is
true that by expanding sufficiently the
same final temperature can be obtained
without compression, but the average
pressure will be low, and consequently
less available for the production of power.
To produce anything like an expansion
of five times without compression the

pressure would fall below the atmos-
phere, and it would be necessary to ex-
pand into a partial vacuum, and use a
condenser and vacuum pump, as is done
in the steam engine. Compression makes
it possible to obtain from heated air a
great amount of work with but a small
movement of piston, the smaller volume
giving greater pressures, and thus ren-
dering the power developed more mechani-
cally available. The higher the maximum
temperature the greater the amount of
compression which can be used advan-
tageously. There is a degree of com-
pression for every temperature, beyond
which any increase causes a diminution
of the power of the engine for a given
size.

The compression in the author's engine
is 40 lbs. per square inch above the at-
mosphere, and he has accordingly con-
fined himself to the comparison of
engines employing this amount of com-
pression with those using no compres-
sion. Now, seeing that this difference
is produced between engines of types 1
and 3 by the simple difference of cycle,
when there is no loss of heat through
the sides of the cylinder, the question
arises which engine would give the great-
est effect, which engine in actual prac-
tice, with a cylinder kept cold by water,
would come nearest to theory ? In which
of the engines would there be the smaller
loss of heat?

The amount of heat lost by a gas in
contact with its enclosing cold surfaces
depends, first, on the difference in tem-
perature between the gas and the cooling
surfaces ; secondly, on the extent of sur-
face exposed ; and, thirdly, on the time
of exposure. It would be very difficult
to make an accurate numercial compari-
son between the engines, but all to be
shown is, that in the one the loss of heat
must be less than in the other.

To compare the two engines, take
equal movements of the pistons from a
maximum temperature of 1,537° Centi-
grade. In the engine working without
compression this temperature is attained
at the middle of its stroke, when the
piston has moved through 1 cubic foot ;
the average temperature, while it moves
to the end of its stroke, is about 1,300°
Centigrade.

Now, in the compression engine the
maximum temperature is attained at a

THE THEORY OF THE GAS ENGINE.

359

point when the piston has moved through
0.39 cubic foot : suppose it to move to
1.39 cubic foot, it has moved through 1
foot in the same time as the first engine.
Then, as the temperature at the middle
of the stroke is 953° (Fig. 4) it follows
that the average during this movement
is not higher than 1,000° Centigrade, but
the space containing the heated air has
increased from 0.39 cubic foot to 1.39
cubic foot, and with it the cooling sur-
face ; whereas the space containing heat-
ed air in the first engine has, during the
same amount of movement, increased
from 1 cubic foot to 2 cubic feet. It
follows that as the temperature in the
compression engine is 1,000° Centigrade
during the same time as the temperature
in the first engine is 1,300° Centigrade,
and as the surface in it for cooling is
also less, the amount of heat lost by the
air must be less in the portion of the
stroke under consideration. During the
portion of the stroke remaining, 0.61
cubic foot, the temperature of the heated
air is low, falling to 648° Centigrade at
the end of the stroke; it follows that
very small comparative loss results. Al-
together the loss of heat by the com-
pression engine will be the least.

It will be seen from Fig. 1 that there
is a further cause of advantage. While
the pressure and temperature are falling
on adiabatic line 1, the work done by 1
cubic foot of air on expanding to the
middle of the stroke at a temperature of
953° Centigrade is 7,888 foot-pounds,
from 953° Centigrade to 648° is 3,202
foot-pounds, that is, 7,888 foot-pounds
of work are performed by the engine
during a movement of the piston equal
to 0.61, while in the engine without com-
pression a movement of 1.00 cubic foot
only does 5,731 foot-pounds.

The compression engine during this
portion of its stroke has converted the
heat entrusted to it into work at twice
the rate of the other engine. This is a
great point. Any method which con-
verts the heat into work with the utmost
possible rapidity, by reducing the time
of contact between the hot gases and
the cylinder, saves heat and enables the
theory of the engine to be more nearly
realized.

Taking all circumstances into con-
sideration, it is certainly not over esti-
mating the relative advantage of the com-

pression engine to say that it will, under
practical conditions give, for a certain
amount of heat, three times the work it
is possible to get from the engine using
no compression.

It will not be necessary to discuss the
theory of type 2 in respect of loss of heat
to the sides of the cylinder, as it is not
much used, and has hitherto failed to
yield results in any way equal to type 3.
It will be seen, however, from Fig. 3,
that the conditions are not so favorable
for a minimum loss of heat as in type 3.

The temperature from the moment of
admission at c, to the point of cut-off
at e, is kept constant at 1,537° Centi-
grade, so that the loss of heat must be
great, both the surface exposed and the
mean temperature being high. It is the
less necessary to discuss this point in
the slow combustion engine, as the pos-
sibility of using a hot cylinder and piston
reduces the loss by attaining a tempera-
ture not far removed from the entering
air.

It will be interesting to calculate the
amounts of gas required by these three
types under the supposed conditions,
and for this purpose an analysis of Man-
chester gas, and also of London gas, has
been used as the basis of calculation.

ANALYSIS OF MANCHESTER COAL GAS.
BY BUNSEN AND ROSCOE.

Hydrogen 45.58

March gas 34.90

Carbonic oxide 6.64

Olefiant gas or ethylene.. . . 4.08

Telrylene 2.38

Sulphuretted hydrogen .... 0 . 29

Nitrogen 2 . 46

Carbonic acid 3 . 67

100.00 volumes.

Of this gas 1 lb. at atmospheric
pressure and 17° Centigrade measures
30 cubic feet, and evolves on complete
combustion 10,900 heat-units Centigrade,
equivalent to 15,146,640 foot-lbs. 1
cubic foot of this gas will therefore
evolve on complete combustion heat

equivalent to ?M*M1? = 504,888 foot-
30

lbs.

To obtain an idea of the difference in
heating power of the different gases,
there is given here a recent analysis of
' London gas.

360

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

ANALYSIS OF LONDON COAL GAS.

(A.) . (B.)

Hydrogen 50.05 51.24

March gas ,....32.87 35.28

Carbonic oxide 12.89 7.40

defines 3.87 3.56

Nitrogen — 2 . 24

Carbonic acid 0.32 0.38

Taking the average of the two analyses,
1 lb. weight of this gas at atmospheric
pressure and 17° Centigrade, measures
35.5 cubic feet, and evolves on complete
combustion 12,500 heat-units Centigrade,
equivalent to 17,370,000 foot-lbs., 1 cubic
foot of this gas will therefore evolve, on
complete combustion, heat equivalent to

=^=■=489,268 foot-lbs.
do. 5

The difference between the heat evolved
by these gases is but small. As Glasgow
coal gas is of a high illuminating power,
it will be richer in defines, and the
heat evolved per cubic foot will be some-
what greater. Taking 505,000 foot-lbs.
as the amount of heat evolved by 1 cubic
foot of coal gas, the result is probably
very near the average to be obtained
from the coal gas of most towns. The
number of foot-lbs. required for 1 HP.
for one hour are 33,000x60=1,980,000.
It therefore follows that if the whole
heat to be obtained from* gas were con-
verted into mechanical work, 1 HP. for

one hour requires ' „ ' _ =3.92 cubic
505,000

feet.

Now, taking the three types of en-
gines, the amount of gas required by
each to give 1 IHP. per hour would be
as follows:

AMOUNT OF GAS REQUIRED BY THREE TYPES
OF ENGINE.

3 92
Typel. (f2i=18-3 cubic ft. per HP. per hr.

q qo

A 0.36-109

Q QO

0.45

If these engines be worked without
loss of heat through the sides of the
cylinders, but the expanding gases fall-
ing in temperature only through doing
work, the above results would be ob-
tained.

It is interesting to compare the con-
sumption of gas by fhe engines in actual

practice, to see in what order it stands.
Results have not been obtained from en-
gines of equal volume swept through by
the piston, but it is at once seen that
the order is in accordance with what is
required by theory.

AMOUNT OF GAS CONSUMED BY THE THREE
TYPES OF ENGINE HITHERTO IN PRACTICE.

1. Lenoir. .95 cu. ft. per indicated HP. per hr.
Hugon..85

2. Brayton.50 "

3. Otto.... 21 "

For the Lenoir and Hugon engines the
results of experiments by Mr. Tresca, of
Paris, have been taken, as stated by
Professor Thurston, corrected for an
error into which he has fallen. He states
the consumption of the engine to be 32
cubic feet per IHP. per hour, and then
goes on to say that on the brake 4 HP.
is obtained, while 8.6 is indicated. He
has neglected to deduct from the gross
indicated power in the cylinder, the
pump resistance, and thus calculates the
consumption on the gross indicated, in-
stead of on the available indicated
power. The available indicated power
is not more than 5.2 HP., and the con-
sumption is not less than 50 cubic
feet per IHP. per hour.

For the "Otto" engine have been
taken the figures given by Mr. F. W.
Crossley. It is seen that the results
are much what would be anticipated
from the theory already developed. The
difference between types 1 and 3 is
greater than theory would indicate ; but
at the time the Lenoir engine Was in
use, the imperfection of the igniting ar-
rangements and the rapid heating of
piston, and consequently of the entering
gases, made its action diverge much
more widely from theory than in the case
with the " Otto." The latter engine not
only has the advantage of a better
theoretical cycle, but the arrangements
are of a nature to secure a greater per-
fection of action, and consequently a still
closer- approach to theory. An amount
of about 18 per cent, of the heat used by
it is converted into work, but only 3.9
per cent, by the Hugon engine.

In types 1, 2 and 3, which have been
discussed, it has been assumed that in
each case the expansion doing work was
carried to twice the volume of the air
before compressing.

THE T1IKORY OF THE (JAS ENGINE.

361

Fig. 6

is a

diagram
author's engines which

from one of the
belongs to type
3. It will be observed that in this en-
gine the expansion is only continued un-
til the volume of the hot gases becomes
equal to the volume before compression.

Now the work actually given by 1
cubic foot of combustible mixture in the
author's engine, as will be seen from Fig.
6, is G,851 foot-lbs. The full lines are
the diagram lines from the engine ; the
dotted lines are the lines of compression

Fig.6.

PARTS OF THE STROKE.

Diagram from Clerk's Gas Engine, cylinder, 6 ins. diameter, 12 ins. stroke, 150 revolutions per
minute. Mean available pressure 70.1 lbs., 9 IHP. The maximum pressure is 220 lbs. per
square inch above atmosphere. The pressure before ignition is 41 lbs. per square inch
above atmosphere. The lower dotted line shows compression without loss of heat, to the
same volume as exists in clearance space. Temperature before compresson 17°. 3 C. (60° F.)
Temperature after compression 150°. 5 O. The upper dotted line shows the work done by
air heated to 1,537° C, supposing it to lose no heat during expansion, except by doing
work. The actual diagram shows a mean pressure during nine-tenth of stroke of 78 lbs. on
the square inch, which is equal to 6,851 foot-lbs. per cubic foot of combustible mixture
used. The dotted lines show an available pressure of 89.8 lbs. per square inch, which is

equal to 7,888 foot-lbs. per cubic foot of air compressed. Duty =24416— 0323.

Taking the amount of work to be ob-
tained from a cubic foot of air com-
pressed to 40 lbs. above the atmosphere,
and then heated to 1,537° Centigrade,
expanding as the piston moves to its
volume before compression, and then ex-
hausting, it will be found to give the
following results :

1 cubic foot of air (17° Centi-
grade and 760 milimeters
mercury) at constant vol-
ume requires to heat it ,
from the temperature of f24'416 foot-lbs
compression 150\5Centi- |
grade to 1,537° Centi- |
grade, heat equivalent to J

.Maximum pressure in lbs. )
per square inch above [-
atmosphere )

Pressure at end of stroke in /
lbs. per square inch f

Mean pressure during avail- )
able part of the stroke [
above atmosphere )

Temperature at the end of ) oe0o n ♦• a

the stroke [ 9o3 Centigrade

Work done on the piston

220 lbs.

89.8

^ . 7,888

7,888 foot-lbs.
32

and expansion without loss or gain of
heat, except by work done on or by
the air under similar conditions of
temperature and compression. It will
be observed that the compression line
and the dotted line are very close to-
gether ; no heat seems to be lost to the
sides of the cylinder during compres-
sion ; the loss of heat to the water-jacket
is balanced by the gain of heat from
the piston, which must necessarily be
much hotter than the cylinder sides, as
it only loses heat by contact with the
cylinder and by the circulation of air
in the trunk. The temperature at-
tained at the commencement of the stroke
is in both esses identical, 1,537° Centi-
grade ; the temperature at the end of
the stroke without loss of heat is 953°;
the temperature in the cylinder at the
end of the stroke is 656° Centigrade.
The diameter of the cylinder from which
this diagram was taken is 6 inches, and
, ahe length of stroke 12 inches. This
Appears a very small loss of heat from a
I tame filling the cylinder, considering the
' surface exposed and the great difference

362

VAN NOSTRAND'S ENGINEERING MAGAZINE.

of temperature between the ignited gases
and the enclosing walls. Is it to be con-
cluded, then, that the loss of heat to the
cylinder during the time of the forward
stroke is only 953°-656° = 297° Centi-
grade? On this assumption the duty of
the engine would be —

6,851
24,416

= 0.286,

and the consumption of gas per indicated
HP. per hour would be —

^-^=13.7 cubic feet,

but the consumption is 22 cubic feet per
indicated HP. per hour, so that there
has in some way been lost much more
heat than is to be accounted for by the
temperatures as determined by the dia-
gram. The duty of the engine is —

The duty of the engine expanding to
the same volume as the mixed gases be-
fore compression is —

Gas required
per IHP. perhr.

Duty without loss of heat to \ n O0Q
sides of cylinder j" u • °46

I 0.286
!■ 0.178

Cub. ft.
12.1

13.7

22.0

Duty with loss of heat as
shown by diagram

Duty as determined by experi-
ment

Now the number of cubic feet of com-
bustible mixture required to produce 1*
HP. for one hour in the author's engine
is —

1,980,000

Centigrade to 1,537° only 0.0482 cubic
foot of coal gas is required, yet although
there is present 0.0761 cubic foot, or 1.58
time the amount necessary, the tempera-
ture does not rise any higher. Why is
this?

Before going into the question, it is
better to determine as nearly as possible
what becomes of 100 heat units used by
the engine. The exhaust being dis-
charged at a temperature of 656°, and
the temperature of the air before com-
pression being assumed at 17°, it fol-
lows that the exhaust from 1 cubic foot
carries away with it (656—17) X 17.61 =
11,253 foot-lbs.

The work done by the cubic foot of
mixture is 6,851 foot-lbs., and the equiva-
lent in foot-lbs. of the gas present in 1
cubic foot of explosive mixture is 0.0761
X 505,000=38,430 foot-lbs. The heat is
therefore disposed of as follows :

Heat-units
Foot-lbs. percent.

Work done by 1 cubic foot ) „ g^ *„ g.>
of mixture ) '

Mechanical equivalent of )
heat discharged with the V 11,253 29.28
exhaust )

Mechanical equivalent of )
heat passing through sides > 20,326 52 . 89
of cylinder )

38,430 100.00

6,851

289.

The amount of gas in the engine per

cubic foot of mixture, ^^=0.0761 cubic

•289

foot, or ^ of the total volume of gaseous

mixture passed into the engine. If only
the amount of gas necessary to heat the
air to the required temperature is pres-
ent, 1 cubic foot requires, 0.0482 cubic

foot of coal gas, or about — of its vol-

ume ; that is, although to heat up a cubic
foot of inflammable mixture from 150°

This investigation is only approximate.
The determination, with anything like
possible physical accuracy, would require
an examination of many points involving
months of continuous work. It is the
author's intention to make an accurate
research into the phenomenon attending
the use of the gas engine, for the pur-
pose of obtaining the physical constants
necessary to calculate exactly the con-
sumption of any power, size, and theory
of gas engine, such as it may be possible
to construct in the future. For. the
present, however, it is only necessary to
discuss the principles in such a manner
us to clearly show where original re-
search is required. More than one-half
of the total heat given to the engine
passes through the sides of the cylinder
and is lost. How is this enormous loss
of heat sustained, while only a compara-
tively small fall of temperature takes
place below the adiabatic curve ?

THE THEORY OF THE GAS ENGINE.

863

This loads back to the question of
the gas present in excess of the amount
necessary to raise the temperature to
1,537° which has already been noticed.
At this point it is necessary to consider
the gas engine as something different
from a hot-air engine.

The chemical phenomena attending
combustion now require consideration.
If 2 volumes of hydrogen be mixed with
1 volume of oxygen (the proportions
necessary for complete combination of
both gases to form water), and be ignited
in a closed vessel in such a manner that
the maximum pressure may be measured,
it will be found that the pressure is a
much lower one than would be expected
if the complete combination of the two
gases took place at once, and the whole
heat due to this combination were de-
veloped. That this is not due to loss of
heat to the sides of the vessel has been
shown by Bun sen. He proved that the
ratio of rise in pressure is exceedingly
rapid compared to the rate of fall of
pressure. The time taken for the in-
flammation of the whole volume of mix-
ture is the time of attainment of the
maximum pressure. In his experiments
he used only a very small tube, which
contained a volume of gaseous mixlure,
8.15 centimeters long, by 1.7 centimeter
in diameter, and the entire length of
this column was traversed by the electric
spark, in order that the inflammation of
the whole mass in the tube might be as
nearly instantaneous as possible. In
practice he succeeded in producing a
maximum temperature in so short a time
as 4o100 part of a second. By examining
the light from the explosion through a
revolving disc provided with radiating
segments, the rate of revolution of the
disc being known, he determined the
duration of light within the tube, and
therefore the duration of a temperature
not far removed from the maximum.

The duration of the illumination was
found to be ^g-of a second. A maximum
pressure, obtained in so short a time,
with a duration so relatively long, makes
it impossible that loss of heat through
the sides of his tube could have affected
his experiments. The cause, therefore,
of the pressure falling so far short of
what it would be if the combination took
place completely, is simply this, that the
temperature is so high that complete com-

bustion is impossible. The temperature,
and therefore the pressure produced by

the combination of any leases, is limited
by the dissociation or decomposition of

their products of combustion.

When any two gases combine, say (H)
and (O) to produce water, what happens

is this. The temperature rises nil a
point is reached, when any further rise
would decompose the water which is
already formed; and if the gases are
kept at this temperature, no further com-
bination will take place. If the tempera-
ture is lowered, further combination
takes place until it is low enough to
allow of the existence of steam without
decomposition.

The temperature at which steam can
exist as steam without its partial resolu-
tion into hydrogen and oxygen gases is
not a high one. At 960° to 1,000° Centi-
grade Deville has proved that it com-
mences to decompose, and at 1,200°
Centigrade, considerable decomposition
takes place, the amount of decomposition
increasing as the temperature rises : for
each temperature there is a proportion
of steam to free gases, which is constant,
and does not change till the temperature
changes. The same law holds true for
carbon dioxide ; at high temperatures it
decomposes into carbonic oxide and free
oxygen.

Bunsen attempted to determine the
temperature attained on the explosion of
a mixture of hydrogen and oxygen, a
pure electrolytic mixture. He found
that the maximum pressure attained by
such a mixture is 10 atmospheres, the
temperature before ignition being 5°
Centigrade. From this he calculated
the temperature produced, but in doing
so, as Berthelot afterwards pointed out,
he neglected the fact that when these
gases combine, 3 volumes of the gases
j form 2 volumes of steam gas, and con-
sequently if complete combination is
i assumed, and it be supposed that the
i pressure is produced by steam only, the
j volume, before ignition, must be calcu-
I lated at two -thirds of that taken by the
i mixed gases. But as it is known that
combination is incomplete, at the lowest
assignable temperature of the combus-
tion, and it is not possible to tell the
amount of combination at a given press-
ure without knowing the temperature,
this cannot be assumed.

364

VAN NOSTRAND'S .ENGINEERING MAGAZINE.

As in determining temperature by an
air thermometer it is necessary that the
amount of air in the thermometer should
be constant at the different temperatures,
it is evident that the temperature of an
explosion cannot be known from the in-
crease in pressure unless the chemical
changes taking place do not alter the
volume of gases under observation.

In calculating the temperatures at-
tained in the author's engine, this fact
has been kept in view. The capacity of
the space at the end of the cylinder was
carefully taken by filling with water and
weighing the water. As the proportion
of the combining gases to the excess of
oxygen or free nitrogen is very small,
only one-thirteenth of the whole volume
used being combustible gas, the space
may be considered as simply filled with
heated air, and the contraction caused by
the formation of H20 and C02 neglected,
especially as an increase in volume fol-
lows the combination of the olefines with
oxygen. 2 volumes of H combine with
1 volume of O, forming 2 volumes of
steam. 2 volumes of marsh gas (CH4)
require for complete combustion 4 vol-
umes of O, and form 4 volumes of H20
and 2 volumes of C02. »2 volumes of
carbonic oxide (CO) unite with 1 volume
of O, forming 2 volumes of C02. If the
olefines in coal gas be taken as of an
average composition of C3H6, then 2
volumes require for complete combustion
9 volumes of oxygen, forming 6 volumes
of H20 and 6 volumes of C02.

Now taking the composition of coal
gas as below the noted amounts of oxy-
gen are required for combustion, and
the given volumes of the products are
formed —

vols.

H=50

CH4=33

CO=13

C3H6= 4

vols,
requires 25
" 66
" 6.5

vols.
O=50 H80 produced
0=99 C04&H20 "
0=13 C02
0=24 C02&H20 "

100

115.5=225.5 gives 186 vols.

The amount of contraction due to com-
plete combustion of this coal gas is small
even when burning with pure oxygen,
225 volumes of the mixed gases becom-
ing 186 volumes after combustion. When
diluted with nitrogen the proportion of
contraction is less and introduces no
serious error. With a mixture of 1

volume of gas to 12 volumes of air, 125
volumes of the mixture before combina-
tion become 122 volumes when complete-
ly combined, at the original temperature,
assuming the water to remain gaseous.
If the curve of the dissociation of water
and carbonic dioxide were known, it
would be possible to show on the indica-
tor diagram the reserve of heat available
at each point of the fall.

What the engineer requires of the
scientific chemist is a curve of the disso-
ciation of water and carbonic acid, at
temperatures ranging from the maximum
produced by combustion down to the
point at which it may be safely assumed
that complete combination is possible.

In Fig. 6 the dotted line shows a fall
of temperature, by hot air doing work
without loss of heat through the cylinder,
and the black line shows the actual fall
of temperature in the author's engine,
with ]oss of heat through the sides of the
cylinder. It is evident then that the
cause of so near an apparent approach to
theory is, that at the maximum tempera-
ture, complete, combination of gases with
oxygen is impossible, and cannot take
place until the temperature falls. As
the temperature' falls the gases further
combine, until a temperature is reached
at which combination is complete.

The loss of heat through the sides of
the cylinder is therefore much greater
than would appear from the diagram. In
calculating the efficiency of the gas en-
gine, all previous observers have assumed
that the loss of heat to the cylinder is to
be obtained from the comparison on the
indicator diagram of the actual expan-
sion-line with an adiabatic line from the
same maximum temperature and press-
ure. So far as the author is aware,
Professor Rucker, of Leeds, was the
first to point out the necessity of taking
into account the phenomena of dissocia-
tion in making such comparisons. Ac-
cordingly, all previous estimates of effi-
ciency, based on the indicator diagram,
are much too high.

The gas engine, then, differs from the
hot-air engine, using air heated in the
manner assumed in the first part of this
paper, in this, that the temperature is
sustained, notwithstanding the enormous
flow of heat through the sides of the
cylinder, by the continuous combination
of the dissociated gases.

THE THEORY OF TJIK GAS ENGINE.

365

Figs. 7 mid S. have been taken from
the k- Journal of the Franklin Institute."
They are Lenoir engine diagrams, and in
them the Bame phenomena aref apparent ;
although rnnning at a very slow speed,
the pressure is most perfectly sustained,
the dotted lines showing the adiabatic,
and the full lines the actual diagram.
The author of the paper in which they
occur, gives the probable maximum tem-

Fig.7.

LENOIR tNGINE.

Diagram at 50 revolutions, cylinder 8% inches
diameter, 16)4 inches stroke.

Fig.8.

LENOIK ENGINE.
Diagram at 45 revolutions, 1 inch=32 lbs.

perature attained al about 1,356° Centi-
grade, and he says, "The dotted line
represents the theoretical curve of ex-
pansion, taking into account the loss of
heat and consequent fall of pressure, due
to the work done (which is the proper
theoretical curve for an indicated dia-
gram). The temperature at the end of
the stroke, indicated by this line, would
be 2,156° Fahrenheit (1,180° Centigrade).
The final temperature shown by the dia-
gram, supposing there be no leakage, is
1,438° Fahrenheit (781° Centigrade), and
the difference 718° Fahrenheit (399°
Centigrade), is the quantity of heat ab-
sorbed by the water-jacket by which the
cylinder is surrounded."

" It will be observed that the explo-
sion takes place so late in the stroke that
there is a considerable available pressure

at the end of the stroke, which of OOUTSe
is not utilized."

Now if the Lenoir engine had only
lost this amount of heat through the
sides of the cylinder it would have been
very economical, and would have ap-
proached the theoretic consumption
mentioned in the earlier part of this
paper; but the causes of loss are so
great that it never did come anything
near this figure, and an error is intro-
duced through neglecting the effects of
dissociation.

Interesting information, however, is to
be obtained from these diagrams as to
the proportion of gas and air in the mix-
ture used by the Lenoir engine. When
these diagrams were taken the maximum
temperature after ignition was 1,356°
Centigrade ; now in the author's present
engine the maximum temperature is
1,537°; it follows that Lenoir used a
more diluted mixture as the temperature
after ignition was lower. The engine
giving this diagram could not have been
using an ignitable mixture containing
more gas than one-fourteenth of its vol-
ume—a mixture which the author finds
to be easily ignited at ordinary atmos-
pheric pressure. The statement is ofte
made that such a mixture will not ex-
plode except it be first compressed ; this
is incorrect, it is possible to ignite even
a weaker mixture without compression.
Coquillon has determined the limits be-
tween which a mixture of marsh gas
(CH4) and air can be exploded. Mixtures
of marsh gas and air in different propor-
tions were introduced into a eudiometer
and fired by the electric spark, with the
following results :

Marsh gas 1 volume, air 5 volumes.
The spark is without effect. Marsh gas
1 volume, air 6 volumes. Explosion only
occurs in a succession of shocks. This
is the first limit of possible explosion ;
the marsh gas is in excess. Marsh gas
1 volume and 7, 8 and 9 volumes of air
give a sharp explosion. With 12, 13, 14,
15 volumes of air for 1 volume of marsh gas
the explosion occurs, but grows gradual-
ly weaker. With 16 volumes of air the
effect is reduced to a series of slight in-
termittent commotions. This is the
second limit ; the air is in excess.

In Fig. 8, ignitions will be observed
very late in the stroke ; these misses
were caused by the points between which

366

VAN NOSTRAND's ENGINEERING MAGAZINE.

the electric spark is discharged getting
wet and thus preventing the passage of
the spark at the proper time. From
these diagrams, the time, from the begin-
ning of rise in pressure to the attainment
of maximum pressure, is found to be
from one twenty-seventh to one-thirtieth
of a second ; when the ignitions are late
it takes longer, one-twentieth of a second
being required ; that is, the flame has
spread completely through the mass in
one-twentieth part of a second.

Now in the author's engine, calculating
from the moment when the ignition port
is opening to the flame, to the moment
of maximum pressure as found from the
diagrams, it has been ascertained that
the time occupied is an average of one
twenty-fifth of a second, a time nearly
identical with that found for the Lenoir
engine.

If it be admitted that the flame has
spread completely through the mass
when the maximum pressure is attained
in the Lenoir engine, it cannot be sup-
posed that it has not spread in like man-
ner throughout the mass of ignitable
mixture in the modern compression en-
gine. Maximum pressure is the only
outward indication of complete inflamma-
tion ; by complete inflammation is not
meant the thorough chemical combina-
tion of the active gases present, but the
spread of the flame through the entire
mass. That when maximum pressure
has been reached complete inflammation
has also been attained has hitherto been
considered self-evident. It is only lately
that the theory has been advanced by
Mr. Otto that in the modern compression
engine attaining maximum pressure at
the beginning of the stroke, the flame has
not spread throughout the mass of the
ignitable mixture in the cylinder; but that
as the piston moves forward the pressure
is sustained by the gradual spread of the
flame. This supposed phenomenon has
been erroneously called slow combustion ;
if it has any existence it should be called
slow inflammation. It has a real existence
in the Otto engine only when it is working
badly ; but even then maximum temper-
ature is attained, and very distinctly
marks the point of completed inflamma-
tion.

The time taken to attain maximum
pressure is longer in a large engine than
in a small one, because the distance

through which the flame has to travel is
greater. During the investigation al-
ready referred to, Professor Bunsen
determined the celerity of the propaga-
tion of ignition through a pure explosive
mixture of hydrogen and oxygen in the
following manner : the explosive mixture
was allowed to burn from a fine orifice of
known diameter, and the current of the
rate of the gaseous mixture was carefully
regulated by diminishing the pressure,
to the point at which the flame passed
back through the orifice and ignited the
gases below it. This passing back of
the flame occurs when the velocity with
which the gaseous mixture issues from
the orifice is inappreciably less than the
velocity with which the inflammation of
the upper layers of burning gas is propa-
gated to the lower and unignited layers.

The rate of the propagation of the
ignition in pure hydrogen was found to
be 34 meters per second. In a maximum
explosive mixture of carbonic oxide and
oxygen it was not quite 1 meter per
second.

Mr. Mallard has determined the rapid-
ity of the propagation of inflammation
through mixtures of coal gas and air by
this method, and found that the maxi-
mum rate of propagation was attained
with a mixture of 1 volume of coal gas
with 5 volumes of air, and it is 1.01 meter
per second. One volume of coal gas with
6 J volumes of air gave a rate of 0.285
meter, or 11 inches per second.

This is the rate of ignition, it must be
remembered, at constant pressure ; in a
closed tube fired at orie end it would ig-
nite with much greater rapidity. In a
closed space the conditions of inflamma-
tion are quite different. The ignited
portion instantly expands, compressing
the portion still remaining, and thus car-
ries the flame further into the mass, so
that to the rate of ignition at constant
pressure is added the projection of the
flame into the mass by its expansion. To
determine from the rate of ignition at
constant pressure the time necessary to
completely inflame a given volume of
mixture at constant volume is a very
complicated problem, which it is proba-
ble can only be solved experimentally.

The author has found it possible to
ignite a whole mass in any given time
between the limits of one-tenth and one-
hundredth part of a second, by so arrang-

THE THEORY OF THE (J AS ENGINE.

367

ing the plan of ignition that a small vol-
ume of gaseous mixture is first ignited,
expanding and projecting aflame through
a passage into the mass of inflammable
mixture, and thus adding to the rate of
ignition the mechanical disturbance pro-
duced by the entering flame. Ho has
succeeded by this means in producing
maximum pressure in one-hundredth
part of a second in a space containing
200 cubic inches. This rate of ignition
is too rapid, and would not give the en-
gine time to take up the slack in bearings,
connecting rods, Sec. But by firing a
mixture with varying amounts of mechan-

the exhaust valve to open. This may
happen from several causes, a too diluted
mixture, or too little mechanical disturb-
ance by the entering flame; or the igni-
tion may be missed until the pressure
begins to fall by the forward movement
on the piston, when the rate of inflamma-
tion begins to come more nearly to Mal-
lard's number of 11 inches per second.
This slow combustion, or rather slow in-
flammation, is to be avoided in the gas
• engine. Every effort should be made to
! secure complete inflammation as soon
! after ignition as is practicable. The lines
in the diagram show this very clearly ;

COMPRESSION GAS ENGINE.

ical disturbance almost any time of igni-
tion can be obtained between -j-J-g- and y1^
of a second. It does not matter whether
the mixture used is rich or weak in gas ;
the rich mixture can be fired slowly and
the weak one rapidly, just as may be re-
quired. The rate of ignition of the
strongest possible mixture is so slow that
the time of attaining complete inflamma-
tion depends on the amount of mechani-
cal disturbance permitted.

Fig. 9, a diagram from an Otto engine,
shows what happens in a compression
engine of type 3 when the ignition comes
late and the movement of the piston
overruns' the rate of the spread of the
flame. It is then seen that the maximum
pressure is not attained until far on in
the stroke, and as a consequence great
loss of power results, the pressure at-
taining its maximum when it is time for

the normal lines are those in which the rise
is almost straight up from the point of
the beginning of the ignition ; they are
marked a and b ; the line c, although com-
mencing from the beginning of the stroke,
does not record the maximum pressure
till the piston has moved forward one-
third of its stroke, while the line d does
not depart from the compression line
until one-tenth of the forward movement,
and does not attain its maximum till near
the end of the stroke. In the last case
the ignition has been missed until the pis-
ton is in rapid motion, and consequently
the flame is at first unable to overtake it.
The rate of inflammation at constant
pressure has been determined only for
atmospheric pressure ; were it known for
higher pressures it would be possible to
calculate exactly the piston speed which
would prevent any rise in pressure at all.

368

van nostrand's engineering magazine.

Fig. 10 was taken by the author from
the motor cylinder of an American Bray-
ton engine of type 2. It shows how the
pressure is sustained as the ignited gases
enter the motor cylinder in flame. This
is the true slow inflammation engine ; in
it the pressure after ignition is not al-

a perfectly sustained temperature no
power at all could be obtained. That is,
the air would simply expand in volume
without rising in pressure above the
atmosphere, and even without loss of
heat to the sides of the cylinder the
whole heat would be uselessly discharged.

Fig.10.

12 11

_2fi— n

BRAYTON PETROLEUM ENGINE (MOTOR CYLINDER).
Area of piston, 50.26 inches. Stroke, 12 inches. Mean pressure, 30.2 lbs.

lowed to rise, but only increase of volume
takes place ; at about the middle of the
stroke the supply of flame is cut off and
the piston moves on, and the heated gases
expand doing work.

Fig. 11 is the compression pump dia-
gram, which must be deducted before
getting the available indicated power.
The motor-piston was of the same area

In type 3 the perfection of slow com-
bustion would be attained when the flame
spread just as rapidly as the piston moves
forward, and the pressure was never
raised above that due to compression.
The pressure diagram would then give
the ideal results of " gradual expansion
of gases" and a "perfectly sustained
pressure." But this is just the condition

BRAYTON PETROLEUM ENGINE.

Air-pump diagram. Area of piston, 50.26 inches. Stroke, 6 inches. Mean
pressure, 27.6 lbs. Pressure in reservoir, 60 lbs.

as the pump, but had double the length
of stroke. This type of engine is not a
good one for a cold cylinder, the loss of
heat through the cylinder being much
more than in type 3 ; but, as it has been
before said, the possibility of using the
theory in the future with a hot piston and
cylinder renders reference to this engine
interesting. Slow inflammation is a mis-
take if applied to engines of types 1 and
3 with cold cylinders ; in type 1, if the
piston were moving rapidly enough, the
inflammation could be so slow that with

of greatest loss of heat ; sustained press-
ure means sustained, indeed increasing
temperature, and the object to be attained
in a good gas engine is to produce the
most rapid possible fall of temperature
due to work performed, to keep the mean
temperature as low as possible, and it is
only so far as this is successfully done
that economy is possible. Slow inflam-
mation causes loss of heat and power;
rapid inflammation reduces the loss to a
minimum while attaining the maximum
possible power.

THE TI1E0KY OF THE GA8 ENGINE.

369

One more engine may be noticed ; its
diagram is given at Fig. 12. In action it
comes under type 1. but uses a very
large amount of expansion, and is further
complicated by cooling. It is the well-
known Otto aud Langen engine of the
free piston type ; in it gas and air are
taken in for a portion of the stroke at
atmospheric pressure and then ignited
while the piston remains at rest until the
pressure sets it in motion; the piston is free
to move apart from the shaft altogether,
and on the up-stroke it does no work.

of the piston is being gradually clucked
by doing work on air, assuming the i
ton to have no weight, the area of the
portion of the diagram <t c b must be
equal to the part ■■ < d.

It is evident that the lines in the dia-
gram are incorrect : the explosion cannot
fall nearly so rapidly as shown ; c should
be much nearer e. The oscillations of
the indicator have been so great that ac-
curacy is impossible. The fall of the
line d g below d e is caused by the cool-
ing of the gases on the return stroke.

Fig.12.

loot

90-

SO-

50-

T90

F^O

-70

-60

4-50

4-30

OTTO AND LANGEN ENGINE (FREE PISTON).
Percentage of stroke.

From f to a air and gas are taken
into the cylinder. At a the mixture is
ignited and the piston moves to c with
considerable velocity when the pressure
has fallen to the atmosphere. From c
to e it continues to move with continually
diminishing velocity, until at e it comes
to rest and then returns doing work, the
work being equal to the diagram d g e
added to the weight of the piston and
rack through the stroke. It will at once
be seen that as the gases only do work
on the piston from a to c, and this work
is absorbed in giving a certain velocity
to the piston, and from c to e the velocity
Vol. XXVn.— No. 5—26.

engine

the

advantage

consists

In this

more in the large amount of expansion

than the velocity of the forward move-

been taken from a
Crossley ; with ref-

ment of the piston.

The diagram has
paper by Mr. F. W.
erence to it he says :

" The very sudden and extreme rise in
pressure at the moment of explosion is
due simply to the expansion of the gases
under the temperature of the flame. If
this temperature be taken at 5,000°
Fahrenheit, and divided by 520 for the
rate of expansion from an initial tempera-
ture of about 60°, it gives an expansion

370

VAN NOSTRAN-irS ENGINEERING MAGAZINE.

of about 10 times ; and as the gas com-
pound occupied one-eleventh of the
cylinder at the moment of ignition, if it
expands ten times it gives very nearly
the stroke actually taken by the piston.
The 5,000° is an assumption only, but
seems to be confirmed by the amount of
expansion which follows it. After the
explosion the temperature falls almost
instantaneously, as shown by the sudden
drop of pressure in the diagram."

In the author's opinion Mr. Crossley
has completely misinterpreted his dia-
gram. Taking the temperature before
igDition at 60° Fahrenheit, and the maxi-
mum pressure shown on the diagram as
100 lbs. absolute, it follows that the
maximum temperature is not greater
than 2,900° Fahrenheit (1,590° Centi-
grade). It is difficult to see how 5,000°
Fahrenheit can be assumed. The ex-
pansion of the gases by the extreme
movement of the piston following igni-
tion has no necessary relation to the
temperature of the explosion ; but it is
determined wholly by the work done on
the piston by the explosion between the
maximum and atmospheric pressures.
Whenever the gases in the cylinder fall
to the pressure of the atmosphere,
which happens according to the diagram
at about 0.35 of the stroke, the piston is
doing work on air, and the mean press-
ure below the atmosphere from c to e is
ike exact measure of the work previously
done on the piston by the explosion,
which has been expended in giving the
piston velocity. This energy of motion
is now being expended by compressing
the atmosphere. Taking into consider-
ation the weight of the piston and fric-
tion of the rings, rack and clutch, it is
certain that the area of the part of the
diagram a b c must be considerably
greater than c e d ; in the diagram it ap-
pears much less. It should be greater by
the amount of work expended in giving the
piston energy of position, and the amount
lost by friction on the up-stroke.

As a means of showing the nature
of the explosion this diagram is mislead-
ing ; it is certain that the maximum press-
ure was less, and that the fall of press-
ure is nothing like so rapid as it there
appears. Comparing Fig. 12 with Figs.
7 and 8 the difference in appearance is
so striking that it looks as if in one case
the fall in pressure was instantaneous

and in the other gradual ; this would be
remarkable, considering that the maxi-
mum temperatures are very similar. If
the lines in Fig. 12 be corrected and
drawn with the same relation of scale
between pressures and strokes, it will be
found to be very similar in appearance
to Figs. 7 and 8, so far as rate of fall is
concerned. Indeed the advantage claimed
for this engine is a movement of piston
so rapid that its expansion is complete
before much heat is lost to the sides of
the cylinder, which is inconsistent with a
fall of pressure more rapid than in the
Lenoir engine.

To go completely into the points of
originality in these engines would require
a paper on the "History of the Gas En-
gine ; " but it may be well to state the
name of the first to propose each type :

Year.
Type 1. Explosion acting on piston con- .

nected to crank. . .W. L. Wright 1833
Explosion acting on free piston,

Barsami & Matteuci 1857
Type 2. Compression after ignition but at

constant presssure. C.W.Siemens 1860
Compression with increase in vol-
ume F. Millon 1861

Type 3. Compression with increase in

pressure F. Millon 1861

After ignition but at constant
volume

So far as the author has been able to
ascertain, these are the names of the first
to propose distinctly each of the three
types of gas engine.

From the considerations advanced in
the course of this paper, it will be seen
that the cause of the comparative ef-
ficiency of the modern type of gas en-
gines over the old Lenoir and Hugon is
to be summed up in one word, " com-
pression." Without compression before
ignition an engine cannot be produced
giving power economically and with
small bulk. The mixture used may be
diluted, air may be introduced in front
of gas and air, or an elaborate system of
stratification may be adopted, but with-
out compression no good effect will be
produced.

The proportion of gas to air is the
same in the modern gas engine as was
formerly used in the Lenoir, the time
taken to ignite the mixture is the same,
the only difference is compression. The
combustion, or rather the rate of inflam-
mation, is indeed quicker in the modern
engine because the volume of mixture

THE THEORY OF THE GAS ENGINE.

371

used at each stroke is greater, and yet
the time taken to completely inflame the
mixture is no more than in the old type.
The cause of the sustained pressure
shown by the diagrams is not slow in-
naniniation (or slow combustion as it has
been called), but the dissociation of the
products of combustion, and their grad-
ual combination as the temperature falls,
and combination becomes possible. This
takes place in any gas engine, whether
using a dilute mixture or not, whether
using pressure before ignition or not,
and indeed it takes place to a greater ex-
sent in a strong explosive mixture than
in a weak one.

The modern gas engine does not use
slow inflammation (or slow combustion if
the term be preferred), but when work-
ing as it is intended to do, completely in-
flames its gaseous mixture under com-
pression at the beginning of the stroke.
By complete inflammation is meant com-
plete spread of the flame throughout the
mass, not complete burning or combus-
tion. If by some fault in the engine or
igniting arrangement the inflammation is
a gradual one, then the maximum press-
ure is attained at the wrong end of the
cylinder, and great loss of power results.

Compression is the great advance on
the old system ; the greater the compres-
sion before ignition the more rapid will
be the transformation of heat into work
by a given movement of the piston after
ignition, and consequently the less will
be the proportional loss of heat through
the sides of the cylinder. The amount
of compression is of course limited by
the practical consideration of strength of
the engine and leakage of the piston,
but it is certain that compression will be
carried advantageously to a much greater
extent than at present. The greatest
loss in the gas engine is that of heat
through the sides of the cylinder, and
this is not astonishing when the high
temperature of the flame in the cylinder
is considered. In larger engines using
greater compression and greater expan-
sion it will be much reduced. As an en-
gine increases in size the volume of gas-
eous mixture used increases as the cube,
while the surface exposed only increases
as the square, so that the proportion of
volume of gaseous mixture used to sur-
face cooling is less the larger the engine
becomes. Taking this into consideration,

it may be accepted as probable that an
engine of about 50 indicated HP. could
be made to work on 12 cubic feet of coal
gas per indicated HP. per hour, or a
duty of about 32 per cent.

The gas engine is as yet in its infancy,
and many long years of work are neces-
sary before it can rank with the steam
engine in capacity for all manner of uses ;
but it can and will be made as managea-
ble as the steam engine in by no means
a remote future. The time will come
when factories, railways amd ships will
be driven by gas engines as efficient as
any steam engine, and much more safe
and economical of fuel. Grs generators
will replace steam boilers, and power
will not be stored up in enormous reser-
voirs, but generated from coal direct as
required by the engine.

The steam engine converts so small an
amount of the heat used by it into work
that, although it was the glory and honor
of the first half of the century, it should
be a standing reproach to engineers and
scientists of the present time having con-
stantly before them the researches of
Mayer and Joule.

APPENDIX.

DATA USED IN THE PAPER ON "THE THEORY
OF THE GAS ENGINE."

Specific heat of air at ) _
constant volume. ) ~
Specific heat of air at f _

0.169 ; water 1.00
0.238

17.6 foot-lbs.

constant pressure r
Mechanical eqivalent )

of heat ioot-lbs. V =1389.6

Centigrade

Specific heat of air at^

constant volume

in foot lbs. for 1

cubic foot at 17°

C. and 760 mm.

barometer

Specific heat of air at

constant pressure

in foot-lbs. for 1

cubic foot from f

IT C. and 760 |

mm J

Weight of 1 cubic ft. )

of air at 17° C. \

and 760 mm )

Burning completely in oxygen, the following
substances are taken as evolving the noted
I amounts of heat iu Centigrade units, per unit
weight of substance burned.

Hydrogen 34,170

Carbon 8,000

Carbonic oxide 2,400

Marsh gas 13,080

defiant gas 11,900

24.8

0.0751b.

372

VAN nostrand's engineering magazine.

REPORT ON THE INCiUNTDESCENT LAMPS EXHIBITED AT
THE INTERNATIONAL EXPOSITION OP ELEC-
TRICITY, PARIS, 1881.*

From "The Engineer."

I. — Desceiption of the Lamps.

The only lamps in the Exhibition which
were purely incandescent in character
were those of Edison and Maxim, in the
United States section, and those of Swan
and Lane-Fox, in that of Great Britain.
The idea represented in these lamps is
essentially the same in all of them, the
differences being, for the most part, de-
tails of construction. They all consist of
a glass envelope more or less spherical in
form, in which is enclosed a carbon loop
made of carbonized organic material, and
supported upon wires of platinum sealed
into the glass. The space in the interior
of the lamp is very perfectly exhausted.

A. The Edison Lamp. — The Edison
lamp is pear-shaped in form. The car-
bon filament is long and fine, and is bent
into the shape of a U. It is made from
Japanese bamboo, cut to the requisite
size in a gauge. In section it is nearly
square, being about 0.3 milimeter on a
a side, the ends being left considerably
wider. The fiber is carbonized in moulds
of nickel, and is attached to the conduct-
ing wires by copper, electrolytically de-
posited upon them.

B. The Swan Lamp. — The Swan lamp
is globular in form, the neck being quite
long. The carbon filament is made from
cotton thread, parchmentized before car-
bonization by treatment with strong sul-
phuric acid. The ends of this filament
are very much thickened, and the loop
has a double turn at the top. Its ends
are clamped in a pair of metal holders,
supported laterally by a stem of glass
which rises through the neck to the base
of the globe. Below, these holders are
fastened to wires of platinum which pass
through the glass.

C. The Maxim Lamp. — The Maxim
lamp is also globular in form, but it has
a short neck. Within the neck rises a
hollow cylinder of glass, supporting upon
its summit a column of blue enamel,
through which pass the conducting wires

• By an Experimental Committee, consisting of
Messrs. George F. Barker, William Crookes, and
others.

of j>latinum which carry the carbon. The
! filament is made from cardboard cut by
I a punch into the form of an M. In sec-
tion, therefore, it is rectangular, and sev-
eral times as broad as it is thick. It is
carbonized in a mould through which a
current of coal gas is passed. After car-
bonization the filament is placed in an
attenuated atmosphere of hydrocarbon
vapor and heated by the current. The
vapor is decomposed, and its carbon is
precipitated upon the filament. In this
way not only are inequalities obliterated,
but the resistance of the filaments may
be equalized, and brought to any stand-
ard required.

D. The Lane-Fox Lamp. — The Lane-
Fox lamp is ovoid in shape, the neck be-
ing in length intermediate between the
two lamps last described. The carbon
is in the form of a horseshoe, and is cir-
cular in cross section. It is made from
the root of an Italian grass, largely used
in France for making brooms. Af-
ter carbonization the filaments are clas-
sified according to their resistances.
They are then heated in an atmosphere
of coal gas, by which carbon is deposited
upon them, as in the filaments of the
lamps last described. The filament in
the lamp is supported by platinum wires,
to which it is attached by sleeves of car-
bon encircling both. These wires pass
through tubes in the top of a hollow
glass stem. Just below the extremities
of these tubes are two small bulbs con-
taining mercury, forming the contact be-
tween the platinum wires sealed into the
glass above and the copper conductor
which enters from below. These con-
ductors are held in place by plaster,
which fills the base of the lamp.

II. — Methods of Measurement.

The question to be determined was
simply the efficiency of these lamps. The
efficiency of a lamp is the ratio of energy
produced to energy consumed, i. e., the
quantity of light given by the lamp for
each horse-power of current which it

REPORT ON INCANDESCENT LAMPS AT THE PARIS EXPOSITION. 373

consumes. The data required to calcu-
late this efficiency may be obtained when
the electromotive force of the current,
the resistance of the lamp when giving its
light, and its illuminating power have
a determined.

1. Electromotive Vbree,— The electro-
motive force, or fall of potential through
the lamp, was measured by Law's method.
A suitable condenser was charged by be-
ing put in communication with a standard
Daniell cell, and then discharged through
a high resistance galvanometer, the de-
flection of the needle being noted. This
condenser was then connected to the two
wires of the lamp, and again discharged
through the galvanometer, the deflection
being made the same as before by means
of a variable shunt conned a with the
galvanometer. Since, with a given con-
denser, the charges it receives are pro-
portional to the potentials of the charg-
ing currents, and since the discharge
deflections of a galvanometer represent
the quantity of these charges, it follows
the electromotive forces are proportional
to these discharge deflections. If, how-
ever, as in the present case, the discharge
deflections are made equal by' means of
shunts, then the electromotive forces are
proportional to the multiplying power of
the shunts.

2. Resistance. — The resistance of t:ie
lamp, when giving its light, was obtained
by making the lamp one side of a Wheat-
stone's bridge through which the main |
current was flowing. The second and
fourth sides were formed of fixed resist- '
ances of known value, and the third side
of an adjustable resistance. When the
bridge is balanced the product of the two
fixed resistances, divided by the adjusted
resistance, gives the resistance of the
lamp at the given candle power.

3. Illuminating Power. — The illumin- 1
ating power of the lamp was measured on !
a Bunsen photometer. At one end of
the bar was the lamp itself, at the other
two standard candles, placed nearly in I
line. The plane of the carbon filament
was placed at 45 deg. to the length of the
bar, and each lamp was measured at 16
and 32 candles.

III. — Apparatus Employeu.

1. Condenser. — The condenser used in
these measurements had a capacity of 1
microfarad, divided into sections of 0.4,

0.3, 0.2, and 0.1. The dielectric was
paraffined mica, and the brasswork was
supported on ebonite pillars. Made by
Latimer Clark, Muirhead, and Co., Lon-
don, and exhibited in their section at the
Exhibition.

2. Galvanometer. — The galvanometer
was a Thomson double-coil astatic instru-
ment, enclosed in a square ease with glass
sides. Measured resistance, 6550 ohnn,.
Used with lampstand and scale in the
ordinary way. Made by Elliot Brothers,
London.

3. Standard Cell. — An ordinary Daniell
cell, the copper plate being immersed in
a saturated solution of pure copper sul-
phate, contained in the porous cell, and
the zinc plate amalgated in a saturated
solution of pure zinc sulphate in the
outer jar. One of a battery of ten cells
forming a part of the Edison exhibit.

4. Resistance Coils. — (a) A set of
I standard coils, measuring from 1 ohm to

1 5000 ohms. All other resistances em-
ployed were standardized by these. Made
by L. Clark, Muirhead, & Co., and a part
of their exhibit, (b) A set of coils used
in the "VVheatstone's bridge. Compared
carefully with set (a). These coils
formed a part of the exhibit of Edison.

5. Wheatstones Bridge. — Four con-
ducting wires of large size arranged on
the table in the form of a rhomb. A test
golvanometer was inserted between the
obtuse angles of the rhomb, and a pair
of shunt wires from the main conductors
were attached at the acute angles. The
first side of the rhomb contained the lamp
to be measured, standing in its place on
the photometer ; the second side contain-
ed a fixed resistance of 5 ohms ; the third
side contained a variable resistance (re-
sistance b) ; and the fourth side a fixed
resistance of 950 ohms. This bridge
formed a part of the Edison exhibit.

6. Photometers.^TliQ photometer em-
ployed was of the Bunsen form, having
a double bar, 80 in. long, graduated in
inches and in candles. The disc was of
parrafimed paper, with a plain spot in the
center. The disc box was movable on
rollers, and contained inclined mirrors to
facilitate the adjustment. The candles
used were of spermaceti, made by Sugg,
of London, to burn 120 grains — 7.776
grms. — per hour. The entire apparatus
was surrounded with heavy black cloth.
Also a part of the Edison exhibit.

374

VAN NOSTRANDS ENGINEERING MAGAZINE.

7. Dynamo- Electric Machine. — An
Edison 60-light machine was used to fur-
nish the current required. In this ma-
chine the field magnets, which are very
long and heavy, stand vertically. The
field is maintained by a shunt current,
regulated by an adjustable resistance in
its circuit. The bobbin is wound on a
cylinder like that of Siemens, from which
it differs, however, in its details. Its re-
sistance was only 0.03 ohm, and the cur-
rent delivei-ed, at .», speed of 900 revolu-
tions, had an electromotive force of 110
volts. A part of the Ediso.n exhibit.

IV. — Resistance of Lamps Cold.

The resistance of the lamps cold was
measured on a Wheatstone's bridge of
the ordinary form and in the usual way.
The Edison lamps were taken at random
from the stock on hand. The Swan
lamps were furnished by Mr. Edmunds,
the Lane-Fox lamps by Mr. Stewart, and
the Maxim lamps by Mr. Lockwood.
Twenty-four of each were taken — except
the Lane-Fox, of which only fifteen were
furnished— and ten selected from these
for the tests. The measurements of the
Edison and Swan lamps were made by
Mr. E. G. Acheson ; those of the Lane-
Fox and Maxim lamps by Mr. H. Crookes.
The following are the results obtained : —

Number.

Edison.

Swan

237 .

.. 74

2 ..

233 .

.. 50

3 ..

268 .

.. 54

4 ..

260 .

.. 73

5 ..

251 .

.. 55

6 ..

228 .

.. 72

7 ..

. 227 .

.. 39

8 ..

249 .

.. 67

9 ..

219 .

.. 55

10 ..

237 .

.. 52

Mear

is, 241 .

.. 59

Lane-Fox.

Maxim

. 53 ..

. 56 ..

. 54 ..

. 50 ..

. 53 ..

. 52 . .

. 57 . ..

. 63 ..

55 ... 72

V. — Measurement of Efficiency.

1. Experimental Results.

A. The Edison Lamp. — In this meas-
urement the entire condenser was em-
ployed. When charged with the stand-
ard cell and discharged through the
galvanometer without shunt, a deflection
of 310 scale divisions was obtained, as a
mean of ten closely accordant experi-
ments. The photometer readings were
made by Mr. Crookes, the bridge read-

ings by Major R. T. Armstrong, and the
galvanometer readings by Prof. G. F.
Barker.

{a) At 16 candles. '

Number Photometer

Bridge Galranome

of lamp. reading.

reading, ter reading

. . 16-

-14.75 .

. 35—34.5 .

.. 16-

-15

35.0

30.5

32.3

! . 16-

-17

33.4

. . 16

-17.5 .

36 0

. . 16-

-15

36.6

34.5

.' .' 16-

-19

37.5

37.7 . .

(b) At 32 candles.

37.2

3 .

32 2

4 .

34 3

5 .

,35.2

6 .

37.9

7 .

38 5

OSP

8 .

36.3

9 .

38.9

10 .

38 8

B. The Swan Lamp. — The entire con-
denser was used in these measurements
also, the deflection being 310 divisions.
The photometer was read by Mr. H.
Crookes, the bridge by Mr. Crookes, and
the galvanometer by Professor Barker.

(a) At 16 candles.

Number.

Photometer. Bridge. Galvanometer.

. 16 .. 119.5

. 136

2 .

. 16

161.7

. 145

3 .

, 16

148.8

. 137

4 .

. 16

113.5

. 122

5 .

. 16

145.9

. 134

. 16

122.1

. 138

7 .

229.0

. 179

8 .

. 16

135.1

. 145

. 16

159.5

. 146

10 .

. 16

171.0

. 145

{b) At 32 candles.

1 .

. 32 .. 123 5

. 121

2 .

. 32

167 2

. 122

3 .

. 32

1552

. 121

4 .

. 32

116.0

. 116*

5 .

. 32

154.7

. 115

6 .

. 32

129.7

. 120

. 32

237.0

. 146

8 .

. 32.

137 5

. 128

. 32

163 0

. 127

10 .

. 32

175.2

. 120

C. The Lane-Fox Lamp. — The entire
condenser was employed, and the deflec-
tion was the same, 310 divisions. Mr.
H. Crookes read the photometer, Mr.
Crookes the bridge, and Prof. Barker the
galvanometer.

REPORT ON INCANDESCENT LAMPS AT THE PARTS IX POSITION. 'M~)

Number. Photonu-tor.

1
2
3
4
5
6

3
4
5
6

r-
I

(a) At 10 candles.
Bridge.

10 170 0

16 1GS 7

16 177 G

16 171 7

16 .. 1710
16 .. 189 5
16 .. 179 0
10 . . 181 1
16 .. 1G1 7

16 1G4 7

(b) At 82 c< indies.

Galvanometer.

.. 150

.. 145

.. 161

. . 1 57

. . 15G

. . 156

.. 156

.. 164

. . 146

.. 148

32
82

33
32
32
32
32
32

178 7

.. 135

175.5

.. 129

181 2

.. 149

175.2

.. 148

175.7

.. 143

192.3

.. 143

186.2

.. 146

184.5

.. 146

167.8

.. 133

172.0

.. 129

D. The JIaxim Lamp. — The entire
condenser was used, as in the previous
cases ; but the deflection obtained was
315 divisions, owing probably to the
higher temperature of the room. Pho-
tometer read by Mr. H. Crookes, bridge
by Mr. Crookes, galvanometer by Prof.
G. F. Barker.

[a) At 16

candles.

Number. Photometer.

Bridge.

Galvanometer.

1 ..

111. 8

115

2 ..

111.3

119

3 ..

1062

t m

111

4 ..

124 7

t #

120

5 ..

111.9

122

6 ..

138.5

121

7 ..

122.0

122

8 ..

, #

115 6

t t

118

9 ..

. .

120.6

123

10 ..

103.0

111

{b) At 32

candles.

1 ..

114.6

K)2

2 ..

114.8

106

:; ..

109.7

100

4 ..

128.6

112

5 ..

114.5

113

G ..

140.8

113

7 ..

126 9

110

8 ..

120.4

105

9 ..

126.5

110

10 ..

109.7

105

E. The

Candle Record.

Candle-

Loss in

Time

n Loss per

power.

Gram.

Min.

Edison

..18.13.

. T-\

..0.2483

Lamp \

..21.22.

. 84

..0.2526,

Swan La

1G&32

..34.15.

126

..0.2695

Lane-Fox )
Lamp \

16&32

..40.70.

.153 75.. 0.2647 |

Maxim j
Lamp \

16 «:

fc32

..26.90.

.101

..0.2586

2. Methods of Calculation.

1. Illuminating Power. — The standard

candle should burn 7.776 grm& Bperma-
ceti per hour, or 0.1296 grm. per minute

The two candles used should burn 0.2593
grm. per minute. The corrected candle

power of the lamp, therefore, is obtained
by the proportion: As 0.2502 is to the

amount actually burned per minute, so
is the observed candle-power to the cor-
rected candle power.

2. Resistance {hot). — From the theory
of the Wheatstone bridge, the resistance
of either side is equal to the product of
the adjacent sides divided by the opposite
side. In the bridge used for the meas-
urement the resistances in the two adja-
cent sides were 950 and 5 ohms. Hence
by dividing their product, 4750, by the
reading of the variable resistance ob-
served, the resistance of the lamp hot is
obtained.

3. Electromotive Force. — In Law's
method the electromotive forces are pro-
portional to the multiplying power of the
shunts employed Since with the Daniell
cell no shunt wTas used, the multiplying
power of the shnnt used with the lamp-
current represented directly the electro-
motive force through the lamp, in terms
of the standard shell. The multiplying
power of a shunt is the sum of the gal-
vanometer resistance and the shunt re-
sistance, divided by the shunt resistance.
In this case the resistance of the galvan-
ometer was 6550 ohms. Hence if S
represents the resistance of the shunt,

obtained by experiment,

6550 + S
S

will

represent the electromotive force. Since
the electromotive force of a Daniell cell is
not 1 volt, as here assumed, but 1.079
volts, strict accuracy would require the
figures given to be increased in that
ratio. Moreover, the small error arising
from the inductive action of the needle
on the galvanometer coils has been re-
garded as unimportant.

4. Current. — By the law of Ohm the
current strength is the quotient of elec-
tromotive force by resistance. Dividing
the electromotive force in volts by the
resistance in ohms the current strength
is obtained in Amperes.

376

VAN NOSTEAND'S ENGINEERING MAGAZINE.

.5. Electrical Energy — The work done
by a current is proportional to the prod-
uct of the square of the current-strength
into the resistance of the circuit. Or,
since the electromotive force is equal to
the product of the current-strength by
the resistance, the energy is represented
by the product of the electromotive force
in volts by the current-stength in Am-
peres. This gives the energy in Volt-
Amperes.

6. Mechanical Energy. — Since an ab-
solute unit of work is done per second
by an absolute unit of electromotive force
in a circuit of one absolute unit of resist-
ance, 1 Volt-Ampere represents 107 abso-
lute units of mechanical work per second,
or 0.10192 kilogrm. -meter. By multiply-
ing the Volt- Amperes by 0.10192, the
product is the mechanical work done in
the lamp in kilogrm.-meters.

7. Lamps per Horse-power of Current.
— One horse-power is 75 kilogrm.-meters
per second. By dividing 75, therefore,
by the number of kilogrm.-meters of work
done in the lamp per second, the quotient
is the number of such lamps maintained
by a horse-power of current.

8. Candles per Horse-power of Current.
— The number of candle-ljghts per horse-
power of current is obtained, of course,

-by multiplying the number of lamps per
horse- power of current by the corrected
candle-power of each.

9. Normal Lamps per Horse-power of
Current. — Conversely, by dividing the
number of candles per horse-power of
current by the normal value of the lamp
in standard candles — in the present case
16 or 32 — the number of normal lamps
per horse-power of current is obtained.

Summary of Mesults.

{a) At 16 candles.

Edison.

Candles 15.38 .

Ohms 137.4 .

Volts 89.11 .

Amperes . . . 0.65L
Volt-Auipeh-es 57.98 .
Kilogram- )

Swan.
,16.61 ,
32.78 .
47.30 .
1.471,
69.24 .

Lane-Fox.
. 16.36 ..
. 27.40 ..
. 43.63 ..
. 1.593..
. 69.53 ..

Maxim.
15.96
41.11
56.49
1.380
78.05

meters,

Lamps per
H.P.

Candles
per H.P.

Lamps of
16 candles
per H.P.

5.911.. 7.059.. 7.089.. 7.939

. 12.73 .. 10.71 .. 10.61 .. 9.48
196.4 ..177.92 ..173.58 ..151.27

. 12.28 .. 11.12 .. 10.85 .. 9.45

Candles 31.11

Ohms 130.03

Volts

Amperes ?

Volt- Amperes
Kilogram- )
meters, f '

Lamps per )
H.P. \ •

Candles
per H.P.

Lamps of
32 candles
per H.P.

(5) At 32 candles.

Edison. Swan. Lane-Fox. Maxim.

33.21 .. 32,71 .. 31.93

31.75 .. 26.59 .. 39.60

98.39 .. 54.21 .. 48.22 .. 62.27

0.7585. 1.758.. 1.815.. 1.578

74.62 .. 94.88 .. 87.65 .. 98.41

7.604.. 9.67 .. 8.936.. 10.03

9.88

7.90

8.47

.307.25 ..262.49 ..276.89

9.60

8.20

8.65

. 7.50
.239.41

. 7.48

VI. — Conclusions.

The following conclusions seem to be
sustained by the results which have now
been given : —

1st. — The maximum efficiency of in-
candescent lamps in the present state of
the subject, and within the experimental
limits of this investigation, cannot be as-
sumed to exceed 300 candle-lights per
horse-power of current.

2d. — The economy of all lamps of
this kind is greater at high than at low
incandescence.

3d. — The economy of light-produc-
tion is greater in high resistance lamps
than in those of low resistance, thus
agreeing with the economy of distribu-
tion.

4th. — The relative efficiency of the four
lamps examined, expressed in Carcel
burners of 7.4 spermaceti candles each,
produced by one horse-power of current
is as follows : — (A). At 16 candles : Edi-
son, 26.5; Swan, 24; Lane-Fox, 23.5;
and Maxim, 20.4. (B.) At 32 candles:
Edison, 41.5; Lane-Fox, 37.4; Swan,
35.5; and Maxim, 32.4. To double the
light given by these lamps, the current-
energy was increased — for the Maxim
and Lane-Fox lamps, 26 per cent.; for
the Edison lamp, 28 per cent.; and for
the Swan lamp, 37 per cent.

The contemplated underground rail-
way of Paris is to be 24 miles long in-
cluding branches and will cost $30,000,-
000, or $1,250,000 per mile; 10 cents
first-class fare, four cents second class
fare, two cents workmen's fare, according
to the class of the "passengaire."

EXPERIMENTAL MECHANICS.

U77

EXPERIMENTAL MECHANICS.

By 0BERLTN smith. Bbxdgbton, N. j.
Tranaaottoiia of the Amerioan society of Bieohanioal Engineers.

There is in tliis country a field of me-
chanical work, which is of vast import-
ance to its industrial interests, and i
to pure science, but which has never been
occupied in am uatie way. I refer

xperimental mechanics, — the ascer-
taining by tentative1 methods the fitness,
strengths and qualities of different mate-
1 their behavior under various
strains, motions, processes and continued
; of their best forms and propor-
tions when worked into parts of machines,
and like considerations.

This work has, so far, been chiefly done
by individuals, as they felt its absolute
need in inventing and developing various
machines. Some of it has been done by
the National Government, principally to
meet its own necessities in naval matters;
a little, in the way of testing boilers, etc.,
to enable it to enforce its steamboat laws.
Other portions of the field have been oc-
cupied by solitary scientific students and
by learned societies, colleges and techni-
-cbools, e. g., the Stevens Institute,
with its valuable tests of strength and
elasticity of metals.

In France there is, I believe, some work
of this kind done at government expense,
but I have forgotten to just what extent;
probably less since she has become a re-
public than w.ien under the " one man
power" regime. In this country we
can hardly hope that our government
will, in our time, be" sufficiently under
scientific influence, or alive to the mag-
nificent industrial economy of the expen-
diture, to devote a few millions to the
endowment of a great National Univer-
sity of Experimental Science, with its
corps of well-paid professors, selected
from the ablest talent of the world, and
its thousand earnest students, all at work
making records which would speedily be
recognized as standards of technical
practice.

In default of this the work must be done,
as heretofore, by our chemists, and engi-
neers, and mechanics, and electricians.
It may be, however, that the time has
come for the introduction of more meth-

od and system, in order that efforts which
are now wasted in needless duplication
may be devoted to more accurate finish-
ing and recording of experiments, and
making them accessible to the mechani-
cal public in a properly indexed form.
Incomplete experiments are the rule,
rather than the exception, when perform-
ed by individuals in furtherance of some
industrial result. This is simply because
the required time and expense deter
them from going any further than is ab-
solutely necessary for the case in hand.

Apropos to this part of the subject, I
have, in common with others, experienced
on numerous occasions the want of a lit-
tle systematized and " get-at-table "
knowledge about some very simple
matters. I have, however, always been
obliged to fall back upon private experi-
ments, which, in the nature of the case,
would have been too expensive if made
thorough enough to be of public value.

To select a few instances : Case " A "
was regarding common spiral springs —
the principles governing their action; the
pressure to be obtained with a given mo-
tion, with given material, given diameter
of coil and wire, and given pitch and
| number of coils. Nobody knew.

Case " B " was in relation to " draw-
; ing " sheet metals, where a flat disk of
| tin-plate, brass, or other thin metal, is
i drawn cold into a cylindrical or conical
form. Who knows the sizes of these
| disks to form a given depth and diameter
of pan or box? Only those manufactur-
ers who have accumulated hundreds of
samples, finding the disk sizes by actual
trial (involving ofttimes tiresome altera-
tions to expensive dies) from which they
can guess approximately the dimensions
for new patterns which they may wish to
make.

Case " C " related to permanent mag-
nets. How short could they be in pro-
portion to their thickness? What attract-
ive power had they in proportion to their
weight, when magnetized to saturation ?
What time was required for such satura-
tion with a given hardness of steel, and

378

VAN NOKTRAND'S ENGINEERING MAGAZINE.

a given strength of electrical current in
a surrounding helix? "Would very mi-
nute magnets (say grains of steel dust)
behave proportionally as larger ones,
etc. *

Case u D " was the simple question :
How fast is it safe to run an ordinary
grindstone, and what is its bursting
speed ? A letter to a prominent grind-
stone manufacturer elicited the reply,
that he did not know, but that Messrs.
So & So ran their stones so fast, and
found it about right. In regard to Case
A, I wrote to gentlemen, eminent for
scientific research concerning the elastici-
ty of metals, and also to a well-known
spring maker. They none of them hap-
pened to have studied the properties of
springs. In relation to Case C, I con-
sulted one of our most celebrated elec-
tricians. It so chanced that he had never
specially investigated the properties of
permanent magnets, so in all these cases
1 labored on alone, having also failed to
find the desired information by referring
to some of the principal mechanical dic-
tionaries, electrical manuals and engi-
neers' handbooks. Perhaps the knowl-
edge searched for is kno^wn to somebody,
and published somewhere, but it certainly
is not readily accessible, as it is in the
case of the steam-engine. The latter ma-
chine has attained a dignity in the me-
chanical world that has given it a litera-
ture of its own, and all the proportions
necessary to a good engine can be found
given in detail in printed tables. This
is, to some extent, true in regard to cot-
ton machinery, and is beginning to be in
plumbing work, and a number of other
industries.

It will be seen that the main idea at-
tempted in the foregoing remarks is, that
the makers and users of machinery in this
country should, for their own pecuniary
benefit, as well as for the interest they
may feel in applied science, combine to
establish some sort of a central council
for experiment and research. The per-
sonel of this council should include such
a number of mathematicians, physicists,
engineers and mechanics, all of the high-
est ability, as would give it the respect
and allegiance of the mechanical public.
Its materiel would be buildings, appa-
ratus, record books and the best attainable
scientific library. Its work would be:
First, the publication and distribution of

official information regarding any techni-
cal subject which the members should
think of sufficient importance, and which
might be suggested by themselves, or by
any correspondent who needed or desired
its investigation ; and, second, the fixing
of standard sizes and proportions where
uniformity of practice is desirable. Its
methods of work would be literary re-
search, correspondence with practical
men, mathematical calculation and me-
chanical experiment. The latter, how-
ever, could in many cases be dispensed
with. To collect, compare, average and
amplify records of other peoples' experi-
ments and practice would be all suffi-
cient.

A notable instance of such work was
the fixing of the excellent " United States
Standard," for bolt threads, nuts, and
heads a few years ago. It was the com-
bined work of individuals (the Messrs.
Sellers) for their own practice, a society
(the Franklin Institute) for the promo-
tion of science, and the United States
Government, which latter made it but
semi-authoritative by deciding to adopt
it in the navy merely.

The important questions arise for con-
sideration, when, to what extent, and by
by whom, shall this work be done ? To
the first, a natural answer is — now. The
second depends somewhat upon the third,
and upon the money and enthusiasm at
command. The third answer is respect-
fully referred to the American Society of
Mechanical Engineers, with the hope
that, if the subject should seem of suffi-
cient importance, it will be properly dis-
cussed. It may be. that your learned
body, representing the best scientific and
mechanical talent of our land, will now
or at some future time, see fit to make a
beginning in this desirable work. Should
such be the case, the possible methods of
action are various. A practicable way
might be to secure co-operation, and to
bring about a systematic division of labor
among the societies and schools that are
already at work, thus increasing their
efficiency many fold. Independent ac-
tion might be the better method, and,
however small the beginning, a nucleus
would be formed, around which would,
in time, accumulate the intellectual and
pecuniary offerings of a grateful and ap-
preciative engineering public.

Should not the engineers of America

EXPERIMENTAL MECHAN [08.

371)

to maintain their credit at home as well
as the great reputation they have gained
abroad, 6ee to bringing about a time when
a peregrinating journeyman will not have
to master a new system of hieroglyphics
upon the drawings at every shop he works
in, — when every shop owner will not
have to select to suit his fancy from a
dozen assorted brands in buying a wire
gauge ; and figure out twenty different
sized pulleys to coax on to his line shaft-
ing to drive twenty " eighteen-inch "
lathes ; and puzzle his brains establish-
ing for himself standard sizes- and angles
for nut bevels, and machine screws, and
key-seats, and loose collars, and drawing-
boards ; and find in his mechanical dic-
tionary half a dozen speeds, varying
some five hundred per cent, as each and
all correct for turning cast iron, — when
he will not need to build a metal-testing
room of his own, — a time, in short, when
„. '▼ell- done calculation or experiment
shall replace a thousaytd half done, and
system shall replace chaos.

DISCUSSION.

The Pjresident: I think that matter
is a matter worthy of some debate, and a
matter of pretty general interest to us all.
I presume that after the gentlemen have
seen what has been done during the last
few months at the Pratt & Whitney Com-
pany's works, and have seen what ought
to be done at various other establish-
ments that we have visited to-day and at
other times, they will come to the con-
clusion that this work can be systema-
tized by the concerted action of men of
adequate knowledge, skill and experience
in such a way that the world would be a
very great gainer, and that instead of
one or two firms expending twenty, thir-
ty, or forty thousand dollars in experi-
ments in getting results that are only of
value to them, and of limited value even
to them, we should by a proper syste-
matization of methods get for that same
expenditure many times the value, and
get it in a satisfactory and authoritative
form, and in a form that would be acces-
sible and available to all. This proposal,
of course, as you all know, is not a novel
one. The matter has been proposed be-
fore, has been thought of seriously be-
fore, I presume, by every man who has
had much to do with mechanical work ;
and it has even taken promising shape on

several occasions ; but there have always
been difficulties in the way, and the result

to-day has not, been at all satisfactory.
Some of the first attempts that ha\e
been made to secure practical knowledge
by careful and skilfully directed experi-
mentation have been made under the
supervision of the government. A com-
mittee of the Franklin Institute conduct-
ed a series of experiments on the strength
' of iron many years ago, in connection
with the investigation of the cause of
steam boiler explosions, that had gr
value. The results were published in a
public document, which is still obtainable,
although rare. The results were of great
practical value,and remain valuable to-day.
Another investigation, made just a little
later under the auspices of the govern-
ment, was that of Professor Johnston on
the value of American coal, and that docu-
ment, containing Johnston's report, on
American coal, remains to-day one of the
most valuable books an engineer can have
in his library.

Mr. Woodbury : I have tried to obtain
that book— is it obtainable ? I have asked
both booksellers and correspondents and
have been unable to get it.

The President : An attempt was made
a few years ago only, to institute a series
of experiments on the causes of steam-
boiler explosions that should be complete,
exhaustive and valuable. Congress very
liberally appropriated 8100,000 and the
President was authorized to appoint a
board — a commission — which should con-
duct the investigations. The President
was not well acquainted with the men in
the country who are capable of conduct-
ing such an investigation. There was
no Society of Mechanical Engineers
to whose officers he could go and
of whom he could ask the names
of the .leading men in the country
in the profession, and from whom he
might obtain information that should
lead to the formation of a proper commis-
sion. He did the best thing that he
could do under the circumstances, no
doubt. In the Treasury Department
there exists a bureau, presided over by
the Supervising Inspector General of
Steamboats. The President made him
the chairman of this commission, and ap-
pointed a body of men whom he sup-
posed were competent to conduct the in-
vestigation and the matter was left in

380

VAN NOSTRAN1TS ENGINEERING MAGAZINE.

their hands. They at once proceeded to
spend money freely — laid quite large
plans ; but for causes that need not be
mentioned here the expenditure of money
was not as wisely made as it might have
been. A large proportion of the appro-
priation was lost from that cause, and
after various mishaps — some due to fault
and some to misfortune — the board died
an unnatural death, leaving their work
incomplete. Some work was done — some
interesting work was done — but the
board has never made a report. The or-
ganization changed in form and changed
in members. Some distinguished men
were on the board at intervals, but the
result has been nil. No report exists.
Notes were taken by the members of the
board, and I presume those notes are in
existence. I was on the board for a time
until my health failed ;. and for that and
other reasons that were obvious to me I
left, and during the period in which I
was connected with it, I know the experi-
ments were conducted carefully so far as
they went. The notes that were taken I
am confident are in existence, and I pre-
sume a concerted movement would
bring out those notes from those mem-
bers of the board who* are still living,
and reports by members to the Treasury
Department. If such reports were made,
they will be published as a matter of
course, and the public document contain-
ing reports so given would then become
accessible to all. But to-day we can
simply look back upon the expenditure
of $100,000 nominally to ascertain the
causes of steam-boiler explosions, with
but little result. If that thing were at-
tempted again, if the same opportunities
were offered to-day, I think it is extreme-
ly likely that results might be- obtained
that would be very valuable and more
than commensurate with the expenditure.
I presume that under similar circum"-
stances the President of the United
States and his advisers would look to a
body like this Society for advice as to
who should be appointed on such a com-
mission and as to what direction, to take,
perhaps, as to methods of investigation.
But the non-success of the board, I have,
no doubt, has hindered investigation in
that direction to such an extent that none
of us here present will ever see the mat-
ter reopened. I presume the investiga-
te causes of steam-boiler ex-

plosions, even were it to be considered as
necessary as it was thought to be then,
will not be again undertaken in a genera- ,
tion.

Fortunately other work, especially of
the Hartford Steam Boiler Inspection
and Insurance Company, and the works
of similar companies in Great Britain,
has enabled us to acquire knowledge that
could not have been acquired even by such
a commission. In the course of their
business operations they have been com-
pelled to study up. the subject. They
have had opportunities of observation
and investigation that no government
commission even could have obtained;
and very fortunately, therefore, as I say,
those commercial bodies are acquiring
information of great value, and the
causes of steam-boiler explosions are
gradually becoming known ; and I sup-
pose all engineers who have watched the
progress of their investigations and
studied the results of their work, xio/ve
come to the conclusion that there are
three principal causes of steam-boiler ex-
plosions ; at least I myself have no hesi-
tation in attributing the great majority
of them to three principal causes ; the
first is ignorance, the second is careless-
ness, and the third is utter recklessness.
Those are the three causes of steam-boiler
explosions. The number of steam-boiler
explosions of which the causes remain
unascertained is a very small percentage
of the total number, perhaps four or five
per cent. I do not know what the figure
is precisely, but it is very small, and
those are principally cases where lack of
knowledge comes simply from lack of
opportunities of observation. So that it
may be stated as a positive fact. I can
say, that we know to-day, that steam-
boiler explosions can be attributed simply
to easily preventible causes, and the
work of such a commission is not to-day
as much needed as it formerly was.- It
remains possible that there are causes of
steam-boiler explosions which are very
rarely operative and which still remain
undetermined, perhaps unsuspected ; but
they are so rare, that they have no direct
value — no direct importance, I should
say. Another attempt was made a little
later to make a serious of investigations
under the auspices of the government,
which resulted more favorably, but still
not as favorably as we might wish. A

i:\PERIMENTAL MECHANICS.

381

Civil Engineers first

ago— think it must be ten
creation of

committee of the American Society of I mediately after its appointment at the

took action several Watertown Arsenal, and received th

at a subsequent day, plans for Hie con-
struction of testing machines, with speci-
ernment commission to investigate the fications and prices that were named.
strength of American materials, They They selected a plan which seemed to
have a standing committee — you will find them the best, directed the construction
their names printed on every issue of the of such a machine, and appropriated the

UTS

now — toward the

years
a gOV-

Xransactions of the Society, on the first
inside page of the cover — a standing
committee on the tests of American iron
and steel. The object of that committee
was to secure the appointment of a com-
mission and the inauguration of an in-
vestigation, such as Mr. Smith has sug-
gested here to-night.

After some years of somewhat ineffect-
ive work, their efforts were finally suc-

-sful, and Congress directed the Presi-
dent to appoint a board to make tests of
iron and steel, and other metal, and to
report results. That board was to con-
sist of an engineer officer of the army,
an engineer officer of the navy, an ord-
nance officer of the army, and three ci-
vilians. This board, so constituted of
persons who were expected to be experts
in the direction that the investigations
were to take, was appointed by the Presi-
dent accordingly, and Congress made an
appropriation of $75,000 to do this work,
with a proviso, as the bill first was passed
through the house, that §15,000 should
be used for the expenses of the board,
and that $60,000 should be appropriated
to the construction of a machine. In

required amount of money for it, The
contract called for an expenditure of
$31,500 on the machine. They were in-
formed that the chief of ordnance (as
this machine was to be placed at the
Watertown Arsenal, and would fall into
the hands of the Ordnance Bureau when
the board had completed its work), would
put in the foundations of the machine,
and thus save the board a considerable
amount of expense. But that was not
stated officially and ultimately; those
foundations were put in at the expense
of the board, so that the major part of
the appropriation of the first year was
expended in the construction of a testing
machine.

But, while waiting for the construction
of this testing machine, which was in-
tended for the testing of very large mass-
es of iron and steel, the board went into
subsidiary investigations, as they consid-
ered them, intending to make the more
important investigations, — the investiga-
tions into the strength of structures and
large masses of iron and steel, — after that
machine was Completed ; and, so long as
that appropriation remained in hand,

the meantime the Committee of the So- they continued their work there, and they

ciety of Civil Engineers, who had been
acting energetically with the appropria-
tion committee to secure the appointment
of the board, found that some influence
was at work that they had not known
anything of, and that influence had se-
cured this peculiar wording of this reso-
lution which was to be a joint resolution
of both houses ; but, by their action, and,
possibly, by the action of friends unknown
to them, the wording was finally changed,
and an appropriation was made of $75,-
000, which was to be used at the option
of the board in their work. Part of the
wording still remained as before ; that
is, they were allowed the use of

expended the full amount of the appro-
priation upon the machines, or upon
these investigations. The amount used
in the personal expenses of the board
amounted to very little. The members
did their work as best they could, and at
an expense that was insignificant, out-
side of actual cost of making tests. The
result of the wrork of the board, so far as
it was carried out, was published in a
public document in 1878. That docu-
ment can be found by members during
the coming summer at Washington, and
I believe it can be procured by applica-
tion to your representatives. But the
appropriation, of course, was soon ex-

$15,000 for the commission. The inter- 1 hausted, and Congress gave another
pretation naturally given to that was that small appropriation the succeeding year,
it was to be used in paying expenses of But after the machine was completed,
the commission, traveling expenses and and after these investigations were well
incidental expenses. The board met im- under way, and the board was just in

382

van nostrand's engineering magazine.

good condition, in every respect, to go
on and do work that should be creditable
and valuable, Congress declined to make
any appropriation, even for the use of
the machine that they had built, and the
board died in consequence of the expira-
tion of its appropriation. The limit of
life for the board was fixed by the
limit of its appropriation. When the ap-
propriation expired the board ceased to
exist. So the board went out of exist-
ence just when it was getting ready to
do its work, and to do good work ; what
it could have done gentlemen can judge
very well by reading the report which
will be published this summer. In that
report you will find what was done with
about fifteen or twenty thousand dollars.
The financial statement is in the report,
and you can judge for yourselves how
much that work is worth, and how well
the expenditure of the board has been
repaid by the acquisition of knowledge.
But Congress seemed to have no appre-
ciation of the importance of that work
and declined to do anything for the
board. An immense amount of influence
was brought to bear upon the appropria-
tion committees, but without the slight-
est effect. Memorials were sent in by
the American Society of Civil Engineers;
by the Society of Mining Engineers ; by
the iron and steel associations ; by the
faculties of all the prominent technical
schools ; by the faculties of some of the
best known colleges ; and recommenda-
tions were made by a large number of
well-known business men, and influence
brought to bear upon the appropriation
committees by members of Congress
from all parts of the Union. Some gen-
tlemen worked very earnestly, and yet
an amount of influence that would natu-
rally and ordinarily secure the appro-
priation of almost any amount of money,
and carry through Congress any reason-
able,— any at all reasonable, — proposal,
failed to secure another dollar of appro-
priation for the board.

The machine, when completed, came
into the hands of the Ordnance Bureau
of the army, and is now in use by them
doing good work. An appropriation was
secured by the Ordnance Bureau, at the
last session of Congress for the continu-
ance of work with that machine, and
there seemed to have been no difficulty
in securing that appropriation, but the

influence of all the business men in the
country, the influence of all the scientific
associations in the country, the influence
of all the faculties of the technical col-
leges in the country combined, could not
succeed in getting the appropriation. So
that gentlemen can see what is to be done
if they expect to accomplish anything
further in that direction. So long as the
interests of the community seem to lie
in the direction of the production of a
testing machine simply, there was no dif-
ficulty. When it seemed likely that the
board would be able to use that machine
effectively, there was difficulty; and I
presume the conditions remain to-day as
they were then. Those are the ways in
which attempts have been made ; and I
have indicated about how much success
has been met with in the way of secur-
ing effective scientific work that would
be valuable to the business men of the
country, under the general administra-
tion of the government. If the attempt
is made to secure such work outside of
the executive departments of the govern-
ment, you will find the difficulty still
greater. Members of Congress do not
like to put money into the hands of ir-
responsible parties. It is much easier to
get money appropriated for use by a de-
partment of the government than for any
work to be done outside ; and the only
chance in this case was to secure the
co-operation of the government officials
with civil appointees.

I am taking a great deal of time, but I
would like to say a few words about some
other work that has been attempted. If
the gentlemen will bear with me I will
go on for a few minutes longer.

Several Members : Go on.

The President : A few years ago two
or three prominent gentlemen connected
with our railroads -came to me and asked
if some such commission could not be
found, if some such method of doing
work could not be inaugurated; or if we,
at the Stevens Institute of Technology, at
Hoboken, could not ourselves start in a
small way some such investigations as
have been called for in the paper just
read. I saw no reason why it should
not be done, and told the gentlemen if
they would give us the necessary capital
and allow us time to do our work well,
that we would accomplish anything in
that direction, and I myself had no ob-

EXPERIMENTAL MECHANICS.

:;s:s

jeetion at all to making the attempt. I
saw the trustees and they naturally were
very glad indeed to lend a hand in the
matter, and the matter seemed to have
been agitated in various directions. Mem-
bers oi the Society of Civil Engineers
spoke of it, and took official action in the
matter in their meetings ; and a good
many individuals at about that time
Led to have taken very much interest
in the subject. That focused the move-
ment at the Institute, and inaugurated
what we called the Mechanical Labora-
tory of the Stevens Institute of Tech-
nology. I had no funds, I had no assist-
ants. I had nothing but the countenance
and the interest of these gentlemen. But
I proclaimed that we would establish a
Lanical Laboratory at the Stevens
rute of Technology, and went ahead.
Fortunately, at this time, the government
A had just been instituted, the com-
mon of which I have just spoken ;
and as chairman of some of the commit-
tees of that board, I was directed to
make certain investigations. I simply
took the apparatus of the Stevens Insti-
tute of Technology, and for a time ap-
propriated it to the use of the board ;
found some bright young men who had
gone through the course, had graduated
creditably, and shown themselves skilled
in manipulation, and put them at work ;
and with, of course a good deal of super-
vision on my part, but with active, ear-
nest work on theirs, we succeeded in do-
ing a large part of the work that actually
was done by the goveimment commission.
A good deal of work was done outside.
Mr. Holley did a good deal ; General
Smith did some. A large amount of very
valuable work was done by a committee
consisting of Commander Beardsley and
some other gentlemen, in the investiga-
tion of the properties' of iron; our Me-
chanical Laboratory took charge of a cer-
tain amount of that work, and that was
a starting-point.

I borrowed money where I could, and
I begged money where I could ; and
where I could not do either, I took it
out of my own pocket. But in various
ways I accumulated apparatus and test-
ing machinery, and set going the Me-
chanical Laboratory of the Stevens In-
stitute of Technology. Well, the amount
of work done there amounts to-day to
about $40,000 worth of experimental

work. That is direct scientific investi-
gation, and directly in the lino that, is
indicated as desirable in the paper that
lias been read. But my duties and the
work that I had accepted from outside
professional practice, proved to be too
mnoh of a load for me, and I broke down;
and during my absence from the Insti-
tute the work done by the laboratory
naturally became less and les.*:. My col-
leagues took a very earnest interest in
what was going on, and much work was
still done ; but the amount of work be-
came gradually less and less, until on
my return I found very little was being
done, almost nothing, in the direction of
investigation; and since I have been
back I have not had the strength or time
to push the experiments as I did at first.
We are now doing a small amount of
commercial work, making examinations
of the strength of materials for the Dock
Department of New York; the Erie
Biilway, and private parties in all parts
of the country. But it is purely com-
mercial work. It does not lead up to
what Mr. Smith asks for ; the scientific
determination of laws and facts in such
form as to be accessible to the public.
And I am not very certain that as mat-
ters go now I can re-establish that ad-
junct to my department on the basis that
I had hoped to put it upon. If I get
strength, and if friends assist us in an
interested, active, earnest way, I have no
doubt we could find funds enough to en-
dow it. But it requires work ; and one
man, I find, cannot do more than about
three men's work. Consequently the
success of such a scheme depends, you
see, not only on the interest of the mem-
bers of the profession, but on the activi-
ty that that interest inspires. The whole
thing is perfectly feasible. The plan of
making such investigations in the man-
ner which is always expected in scientific
work can be carried out. It simply re-
quires brain, physical strength and capi-
tal ; and if the Society can find a way of
bringing those things together it will ac-
complish results that will be simply won-
derful.

Mr. Holley : I would like to add one
word, Mr. President, to what you have
said. I could say a good deal upon the
subject, but the time is passing rapidly.
It must be obvious to the Society that
the Ordnance Department of the United

384

VAN N0STRAN1>'S ENGINEERING MAGAZINE.

States Army does not wish to co-operate
with that perfect harmony with civilians
that might, under some other circum-
stances, have been expected, not to put
it too strongly. Seeing that the Ordnance
Department may not wish to go into that
co-operation with civilians in conducting
these experiments, but that it desires to
control that matter itself, if that is the
only way in which it can be made to help
us in this work, then, certainly, it becomes
the duty of the mechanical engineers to
try to stimulate the Ordnance Depart-
ment to make experiments that will be
useful to us and the industrial arts gen-
erally, and not useful merely to the Ord-
nance Department. I just throw out
that mere hint.

The President : And I would add to
my remarks on the work of the United
States commission appointed to test iron
and steel, that the discovery by the presi-
dent of the board of the inventor of that
testing machine, Mr. Albert Emery, is
enough of itself to justify the creation
of that board, and the expenditure of all
its money. I think the discovering of
Mr. Emery was one of the greatest dis-
coveries of the age ; and the construction
of the testing machine has been one of
the greatest pieces of engineering work
that ever has been done. That machine
has done and it is doing its work ; and if
nothing more has been done by the
board, as I said a moment ago, that is a
great deal, fully enough to justify the
creation of that board, and the expendi-
ture of all the money that has been and
will be expended upon that machine.
The machine is open to the use of the
public, and it is being used to-day very
largely, and is in almost constant use by
our business men. And I would say, too,
that although I do not feel at all satisfied
with the results of my experiments in
the establishment of a mechanical labora-
tory, I think that our success, so far as
we have obtained results, has been quite
sufficient to repay all the expenditure of
time, health, energy, strength and money
that has been made on it.

Mr. Stirling : I would like to call the
attention of the gentlemen to another
way in which we can get the informa-
tion, to some extent, that has been asked
for. Having the good fortune to be a
lieutenant of Mr. Eckley B. Coxe, of
Pennsylvania, I have the privilege of be-

ing under the same roof with one of the
finest technical libraries in the country ;
and in that library we have a book which
is published by the German government,
— I do not know of what bureau in that
government, and that book gives a state-
ment of every article that is published on
every subject in every country. And as
an illustration of what good this is to us>
the other day I had occasion to look up
the subject of the transmission of power
by friction gearing. I asked the librarian
to give me all the literature there was on
the subject, and I got a list of thirty or
forty articles, published in different
languages, on the subject of the trans-
mission of power by friction gearing. I
think that in that way gentlemen can be
posted upon a great deal of this experi-
menting that has been done by individ-
uals, on almost every subject.

Mr. Smith : I would like to say a word
more, if it will not take too much time ;
as this is a subject on which I feel very
deeply. I feel that I am too young a
member of the Society to make a motion
on the subject, and shall not do it to-
night. But I think that a committee
should be appointed to consider the
question, and report at a future meeting,
whether anything can be done by this
Society, or whether the matter should be
left entirely alone. If, however, anybody
here wants to make a motion I shall be
very glad. What is wanted is not only
the ability to get at the technical books
and articles that have been published on
the subject, but a brief resume of them.
An average manufacturer cannot afford
to search through a half dozen learned
books, even if he can get them, and col-
lect all the information that is given there
and condense it. He wants to be able to
correspond with a standing committee of
this association, or some other that is
known as a standard throughout the
country, and get at the best figures,
which ' need not be exactly accurate,
something just to guide him so that he
will not go too far astray on any particu-
lar thing he is working on. It is use-
less to hope, as our President says, for
much money to be spent by the govern-
ment ; still we can all do what we can in
that direction, by bringing it before
Congress and friends who have
influence there. Whatever is gained
will be gained by independent work;

EXPERIMENTAL M KC1I A N ICS.

385

and although it may not be much now,
on account of the want of means in this
Society, yet the Society will grow and we
will get more means, and this expense
might, perhaps, be paid by the members.
It would not be a very great expense to
keep up an organization with which
people could correspond and which would
give the results of what has been done.
After a while it would grow to be of such
importance, that it woukl be a standard
for working from by all progressive men.
And, something I did not mention in the
paper, that is wanted greatly among our
mechanics is a standard of nomencla-
ture. Great confusion results now from
having half a dozen names in different
machine shops for the same thing. That,
and standard sizes of gauges, and the
collection of needed information, and the
answering of questions regarding what
has already been done, would not be such
an immense work, and could be done at
comparatively small cost. Although I
do not think the Society is large enough
to undertake it now, yet we can all use
our utmost endeavors to make the So-
ciety grow, get membership of the right
kind, more money in the treasury, and
after awhile we shall see the importance
of this subject so clearly as to be willing
to spend a little of our money. I shall,
certainly, at another meeting bring about
some kind of a motion for a preliminary
committee to investigate the subject
more at length, if it is not done now by
somebody.

The President : The accomplishment of
anything in that direction will require a
great deal of careful thought, preliminary
work, and cautious procedure. It involves
a good deal more than gentlemen gener-
ally are disposed to anticipate. It means
the devotion of some man or men exclu-
sively to a certain object; and if a manu-
facturer cannot afford to give the time to
the looking up of a half a dozen refer-
ences, it is doubtful if he can find any
other man to give his time to looking up
a hundred references for a hundred dif-
ferent persons. To get good work done
requires the expenditure of a good deal
of money ; but it is a matter that has
been deemed of sufficient importance to
be called to the attention of other lead-
ing societies in the country, all the tech-
nical societies and faculties of technical
schools have considered it as of great
Vol. XXVII— No. 5—27.

importance ; and I have no doubt that
with a special and concerted action, the
time will come when the thing will be es-
tablished. Referring to Mr. Stirling's
remarks, the work he refers to is Carl's
Repertorium, and it was published for
quite a long series of years in Germany,
by the editor Carl ; and he was succeeded
by Schubarth, so that the late issues are
called " Schubarttis llepertoruon." Gen-
tlemen interested in investigations who
wish to look up references, by obtain-
ing a set of that work, will put them-
selves on the track of about all that has
been done in the direction of scientific
and technical research. And then in
reference to what has been done in this
country, turn to the files of the Journal
of the Franklin Institute. I do not
know how many volumes of that have
been published, perhaps sixty or eighty
volumes, but it runs back a great many
years, and contains an account of almost
all the important work that has been done
in this country. The Philosophical
Magazine gives an account of the greater
part of the valuable scientific work done
in Great Britain. The Annales cle Chemie
et cle Physique tells you what has been
done in France; and you will find if you
go to the As tor Library, in New York,
that the librarians can always put you
exactly on the track of what you need if
it is published at all. London Engi-
neering is to the engineer a perfect mine,
and a mine you will never tire of work-
ing.

M. Cailletet has invented a new pump
for compressing gases to a high degree of
compression. The main point in its con-
struction is the method by which he ob-
viates the existence of useless space be-
tween the end of the piston-plunger and
the valve, which closes the end of the
cylinder. This he accomplishes, Nature
says, by inverting the cylinder and cover-
ing the end of the plunger with a con-
siderable quantity of rnercury. This
liquid piston can of course adapt itself
to all the inequalities of form of the in-
terior space, and sweeps up every portion
of the gas, and presses it up a conical
passage into the valve. The valve by
which the air enters the body of the
pump is opened by cam-gearing after the
descent of the piston below the point
where the air rushes in.

386

VAN NOSTRAND'S ENGINEERIIS'G magazine.

PILE-DEI VING FORMULA.*

By A. C. HURTZIG, Assoc. M.I. C.E.
Contributed to Van Nostkand's Engineering Magazine.

In an article on Pile Foundations in
Van Nostrand's Engineering Magazine for
July, reference is made to a " Note on
the Friction of Timber Piles in Clay," by
the author. In addition to this note, he
on a former occasion investigated the
subject of pile-driving, with the object
of obtaining.a simple and practical method
of determining the relations between
weight of ram, fall, " set " per blow, and
supporting power of any pile. This re-
sult when applied to the' experimental
pile driven at Proctorsville, gave a sup-
porting power almost the same as the
actual load that was found necessary to
move the pile.

The inquiry led to the construction of
a set of diagrams, from which by mere
scaling, any particular condition of pile
driving could be obtained when the other
conditions were known. •The use of dia-
grams always commends itself to the
practical engineer who has generally no
inclination to wade through tedious form-
ulae and figures with great risk of error,
when he can obtain the information he
requires in a shorter time and with small
chance of error. In this article is given
the reasoning by which the results were
deduced, and the author claims for these
formulae and diagrams that they are based
on exact scientific principles, and that
since the constants are determined from
a large series of experiments, they are
practically reliable.

In the July number of this magazine
before referred to, a comparison was
made between twenty recognized form-
ulae, and an actual experiment on a
pile at Proctorsville. As was pointed
out, the discrepancies between the two
results are truly remarkable, and none of
the formulae go very near the actual facts.
The main particulars of the experiment
were as follows : (See July number page
23).

* Part of this article is an abstract of a Paper read
by the author at a supplemental meeting of the
Students of the Institution of Civil Engineers, London.

Length of pile =30 ft.

Scantling, 121" x \>> at top. Ill" x \\"
at bottom.

Weight of ram =910 lbs.

Fall of last blows =5 ft.

" Set " at last blow = j- inch.

With these conditions, the author's
formula, as will be presently shown, is

P 625'

in which

Y=" set " of last blow in feet =.03.
X= energy of do. do. in foot-tons =

5x910

2240

= 2.031.

P = extreme supporting power of pile
in tons. Inserting these numerical val-
ues and transposing, the equation be-
comes

P2 + 18.75P-1269 = 0,
whence

P=27.47 tons=61,533 lbs.

The actual load, which caused motion in
the pile was 62,500 lbs., so that the for-
mula gives a close approximation.

In arriving at this result, the author
considered three formulae which are prob-
ably more relied than on any others.

These were

Rankings,

^.E.S.W.A 4E2.S2y\ 2ES.T

_. //4.JU.S.W.A 4Hi*.»'.y*\

Sanders.

:8.y

McAlpine, P=80(W + 0.228 a/A-1)

in which the letters have the following sig-
nifications : .

P= weight to be sup-") -, . ,,

&, -, r f measured in the

ported. y .,

W1 • i - p ( same unit.

= weight of ram. )

h = height of fall. ^ measured

1= length of pile. i- in the

y= depth driven by last blow. ) same unit

S=sectionalareaof the pile, (to any unit).

PILE-DRIVING FOKMULJ-:.

387

E=niodulus of elasticity of the timber
referred to the same units as W. and S.

Kankine's formula is purely theoretical,
and though expressing the true relations
between the quantities, it fails as a prac-
tical formula in that its contents are not
derived from experiment on such a scale
as would justify their use in every-day
pile-driving practice. Thus in this form-
ula the modulus of elasticity has a value
deduced from the elementary experiments
on the strength of materials. Pile heads
under the process of driving are by no
means comparable with the perfect speci-
mens of timber used in laboratory exper-
iments ; yet no allowance is made in the
formula for this fact. It is also so cum-
bersome, as to render its use difficult and
distasteful to the practical engineer.

By putting y—0 it follows that

4.TT Q

P'= W.h.— p,

whence it aj^pears that the supporting
power of a pile is proportional to the
square root of the fall. Now the formula
of Major Sanders gives the supporting
power as proportional to the first power
of the fall, and this relation is evidently
an incorrect one. Sanders' expression
was deduced from experiments, and may
be trustworthy within a certain small
range of conditions corresponding with
those of the experiments. It is probably
admissible when there is a considerable
"set " per blow. In cases of small " set "
it gives excessively high results, and in
the limiting case where y=0 the pile
would support an infinitely great load,
no matter what weight of ram he used, a
a result the fallacy of which is evident.

McAlpiue's formula is of much value,
as having its constants deduced from a
large number of piles, and the form of
his expression, as will be shown imme-
diately, is the same as Rankine's in a par-
ticular case. McAlpine recommends his
result only between certain limits, and
these restrictions render the formula in-
applicable in a great majority of cases.
For instance, it is recommended for falls
between 20 ft. and 40 ft. — limits between
which but few piles are driven — in Eng-
land at least. There is no reason, how-
ever, why McAlpine's experiments should
not be used as a special case for de-

termining the constants for Rankine's
general formula.

Rankine's original expression is this :

P"J

(i)

in which the total energy (W.h) of the
blow is represented as having been de-
stroyed by two processes, viz,.: the com-

pressionl jof the pile, and the energy

(P.y) required to drive the pile through
a distance y. A considerable modifica-
tion is necessary in this owing to various
disturbing influences which are omitted,
but which from their variable and indefi-
nite nature must necessarily be omitted
from a general theoretical investigation.
Firstly, there is the friction of the leaders,
and the atmospheric resistance. McAl-
pine found that a 1 ton ram falling from
a greater height than 40 ft., will not even
in a very well constructed pile engine at-
tain to a greater velocity than if it fell from
40 feet only. This is contrary to the indi-
cations of theory, and it is such discrep-
ancies as this which have to be met in a
theoretical formula by suitable coeffi-
cients. In the next place, as the ram
reaches the pile head in each successive
blow, it meets with a material the elas-
ticity of which is different from what it
was before, owing to the destruction or
modification of the elastic properties of
some or all of the fibers in the pile head.
This effect on the cempression of the tim-
ber, the correct representation of which
will elude all theoretical inquiry, must
again be represented in the formula by
some constant derived from extended ex-
periments. Lastly, there are certain ir-
regularities in the nature of the surface
of the pile, in the verticality of the driv-
ing, &c, which will still further modify
the formula. The remaining energy of the
blow is absorbed in compressing the tim-
ber and imparting motion to the pile.
In Rankine's expression (i) above, the
motion of the pile enters the last term
only, and it is only the first term that
will require modification on account of
the various disturbing influences enu-
merated. For suppose the pile going ^j-
inch per blow or some other extremely
small amount, and suppose at the next
blow it refuses to go at all. The disturb-
ing influence, in the last cases where the

388

VAN NOSTRAND'S ENGINEERING MAGAZINE.

pile is in a state just bordering on mo-
tion, must be exactly the same as they
were when the pile just moved, and they
must consequently appear in the formula
in the limiting case. But then the sec-
ond term (P-fy) vanishes since y=o;
hence the disturbing influences must be
represented in the first term, and the ex-
pression in the limiting case will take this
form:

W.^C.|J .... (ii.)

where C is mere constant.

This case corresponds with the condi-
tions of McAlpine's experiments, and
from these experiments the vulue of C
may be obtained with a considerable de-
gree of accuracy, since observations on
as many as 7,000 differ en t piles were
taken. To compare McAlpine's formula

with (ii) above write W=unity, and — for

-j=- which will be a constant quantity for
4Eb

any particular pile ; (ii) then becomes by

transforming

P=kVh~ .... (iii.)
while McAlpine's formula becomes

P = 18.24y/A" . . . (iv.)

and these two results are quite similar.
The numerical conditions of McAlpine's
experiments are briefly these :

The average driven length of the piles
was 32 ft. Allowing for re-heading, &c,
this is equivalent probably to an average
length of about 36 ft. while driving. The
piles were round straight spruce spars of
an average diameter of 11 inches, or sec-
tional area of 96 sq. inches.

The ram was 1 ton falling through 30
feet. The average distance driven in the
last five blows was 1 inch, the last blow
of the ram driving the pile nil.

The actual weight — found from many
cases — to move a pile so driven was 100
tons each pile.

By inserting in (iii) these numerical
values it reduces to

vc
and by comparing this with (iv) it appears
that

?M=18.24

.\a/c = 4.74 and c = 22.4.

Having found the value of c, Rankine's
expression will now be

WA=5.6^P° + Py

(I)-

This formula will be applicable in any
ground; for since a pile resists motion
by virtue of lateral compression, the
depth driven by the blow is cceteris par-
ibus, the exact indication of the nature of
the ground. It can be no matter at all
what is really its mineralogical character,
except in its effect in opposing the motion
of the pile, and this effect is known by
the measurement of the depth driven
by the blow, or the "set." The very
substitution in the formula of the numeri-
cal value of this " set " at once renders it
applicable to the particular ground in
which the pile is being driven.

Referring now to formula (I), the value
of the ratio of the length in feet to the

sectional area in square inches (-),

practice varies generally between the
limits \ and J. Where round spars are
driven the ratio may be increased to ^,
but this is an unusual case. The average
value of E, the modulus of elasticity for
timber of the fir and pine classes, such as
are commonly used in pile-driving, is 700
tons. Making use of this value of E and

taking values off- )=£, \9 ^, and J, the
numerical equivalents of ' are re-

spectively ^¥, ^T, ^ and -^^ Rep-
resenting now the energy of the blow
(W./i) by x, inserting the above numerical
quantities and transforming, a series of
four formulae is obtained as in the fol-
lowing table (see next page).

These formulae give rise to two sets of
diagrams. For a description of their
construction and use one case will be
taken. The annexed figures refer to. the
first formula in the table.

V' P 500

Taking x and y as variables in this, it is
the equation to a straight line cutting the

. , . P2

axis of x at a point x=— — . The ordinate

500

y of this straight line at any point gives

the set per blow corresponding to the

energy x at that point. For different

PILE-DRIVING FORMULAE.

389

Formula.

500
625

y=¥-

V P 750

y P 1,000

Correspond i nix lengths of
Pile for

f-.2 a

rt x *

33 — th
§«2 II

ft.

36
29
24

»-. c a
ro v uj

a A ,-*>
s . os

*J .S T-H

£w II

cc7"1

ft.
42

28
21

fi y K

ft.

49
39
33
24

arbitrary values of P there are different
straight lines as shown in Fig. 1. To il-
lustrate the use of this diagram, let it be
required to determine the conditions of
driving for a pile which shall sustain a
weight of 20 tons. Taking 3 as a coeffi-
cient of safety, the line P=60 tons will be
the one to consider. This line cuts the
axis at a point where jc=7.2. Here then
y=set=o, that is to say, a ram of one ton
falling 7.2 ft., and driving the pile till it
refuses to move, will be sufficient to enable
the pile to carry a load of 20 tons, and
for this particular case 7.2 ft. is the least
" fall that can be used. If it be desired to
use a 12 ft. fall the energy of blow x=
12x1 = 12 foot tons. The corresponding
value of y=.08 ft., or "set" per blow=l
inch ; and if the driving has been regularly
diminishing down to this point it may
cease, and the pile will safely sustain the
required load.

If now in the formula, y is taken as
arbitrary, while x and P are the variables,
the equation is one to a parabola and the
curves drawn in Fig. 2 represent these
parabolas for different arbitrary values of
the set " set " y. The ordinate to the
curve for any particular " set " per blow
gives the extreme supporting power cor-
responding to the energy x at that point.
For example, required the extreme sup-
porting power of a pile driven by a one
ton ram falling 12 ft. until the " set " per
blow does not exceed £ in. = .04 feet.
The ordinate, for x=12, to the curve cor-
responding to this " set " of .04 ft. is 68,
and 68 tons is the extreme value required.

The remaining case where y and P are
variables x being arbitrary is not of so
much value, since all possible information
required is given in Figs. 1 and 2 for the
particular given conditions of any ma-
chine.

With regard to the experimental pile at
Proctorsville, the value of

s 12X12J
and the formula to be used is
x P
P~625'

Factor of Safety. As pointed out
above, the particular ground in which a
pile is being driven, so far as its resisting
power is concerned, is always taken into
consideration by the mere insertion of
the " set " in the formula. If two piles
be driven to the same resistance, but in
different soils, there is little doubt in the
author's opinion that these two piles
would sustain nearly equal dead weights.
In sandy soils, after a lapse of time, no
doubt the resistance to driving increases,
and therefore the supporting power of a
pile would also generally increase. In
clayey soils probably this improvement
takes place only to a very slight extent.
The great use of a factor of safety is to
cover the irregularities which occur on a
work, and which are not anticipated or
provided for from the office. A contract-
or for example does not always carry out
the work to the letter of the specification,
and a pile ordered to be driven to a cer-
tain resistance under a certain blow, may
be left in a very different state from what
was intended. Again, the formula is
taken to apply to a pile the head of which
is in fairly good condition, but though a
pile head may be battered almost to a
pulp, it is often thought by foremen pile-
drivers not worth while to re-head it if it
is going say J inch when a specification
may require \ inch. It is considered suf-
ficiently near, and is left as driven. But
this idea — perhaps pardonable in an igno-
rant workman — involves a great reduction
in the supporting form of the pile. The
author has seen a spongy-headed pile
driven until it refuses to go ; after being
re-headed the pile has under the same fall
gone f of an inch. Such a thing repeat-
edly occurs. On any small job where
one pile engine is used, it is a simple

390

van nostkand's engineeking magazine.

too

O..90

0.80

0.70

0.60

0..50

Ov-40

Fig. I.

Diagram showing relation between Energy of blow,
Set peTblow,_and Extreme supporting power of afir pile

40 Foot Tons
1.00 Foot

0.20

0.30

0.10

0 5 10 1.5

Abscissas— x=Energy of Blow in foot tons

Formula y=~- ^-350.

40. Foot Tons

PILE-DRIVING FORMl'L.!:.

391

Fig. 2.

100.

Curves of extreme supporting powers of afir pile
under varying Energy of blow for different values of Set.
10 20 30

40 Foot Tons
100 Tons

0 5 10 15

Absci'ssae-=x=Energy of Blow'in foot tons.

Formula v = -^- ^—

y p 500.

40 Foot Tons

392

VAN NOSTEAND'S ENGINEEEING MAGAZINE.

matter to ensure each pile being driven
correctly, but on a large work such as the
author is in charge of, where 15 steam
pile engines are in use and where some
thousands of piles have been driven, it is
certain that a large number will escape
inspection. Then again, here and there,
a stick of timber may get driven of poorer
quality than the surrounding piles, and
after a short time this pile may become
useless for supporting the superincum-
bent structure.

In the course of years it is probable
that data may be obtained, comparing
actual dead weight resistances in differ-
ent soils with the indications of some
theoretical formula, but there will still re-
main the necessity for an arbitrary factor
of safety which will in the judgment of
the engineer suit the particular case in
question. What considerations should
determine the value of this factor ? There
are no means of determining the numeri-
cal equivalents of such irregularities as
are named above, except a comparison
with records of actual works executed.
By a consideration of such works in
Europe the author concludes that with
ordinary piling engines giving from one
to six blows per minute, a factor of safety
varying from 2£ to 5 will include the

range of ordinary practice. Now as far as
crushing of the timber is concerned, a 30
ft. pile 12 inches square will safely carry
50 tons, and as the safe load on a pile is
very rarely if ever made equal to this,
the factor of safety for driving will not
interfere with that for crushing. The
factor deduced — 1\ to 5 — will then not
be too low to meet contingencies, and as
these are the numbers that recommend
themselves by a comparison with recent
practice, the author would adopt them as
the limits for use with the diagrams. The
number 3 is sufficiently high for most
cases.

In regard to piling engines of the Nas-
myth type delivering blows up to a rate
of 60 a minute, experiments have been
made which show that a given energy ex-
pended by such an engine in blows deliv-
ered in rapid succession would do "2\
times the amount of effective work that
could be accomplished by an equal ener-
gy from a hand engine when the blows
follow each other slowly. From this, and
from a comparison with recent works, it
is probable that the diagrams or formulae
would give tolerably accurate results for
the Nasmyth type of pile-driver if the
factor of safety taken were between the
limits 1 and 2.

HOUSE DRAINAGE AND SANITARY PLUMBING.

By WM. PAUL GERHARD, Civil and Sanitary Engineer, Newport, R. I.
Contributed to Van Nostrand's Engineering Magazine.

II.

ESSENTIAL ELEMENTS OF A SYSTEM OF
PLUMBING.

We have thus far considered only the
material, size, general arrangement and
manner of jointing the drain, soil and
waste pipes in a house. We must now
consider what the essentials of the sys-
tem are, in order to secure to the house
perfect immunity from sewer gas. Brief-
ly stated, these essentials are as follows :

1. Extension of all soil and waste
pipes through and above the roof.

2. Providing a fresh air inlet in the
drain at the foot of the soil and waste
pipe system.

3. Trapping the main drain outside

of the fresh air inlet, in order entirely
to exclude the sewer air from the house.

4. Providing each fixture, as near as
possible to it, with a suitable trap.

5. Providing vent pipes to such traps
under fixtures as are liable to be emptied
by siphonage.

EXTENSION OF SOIL AND WASTE PIPES.

The first requirement asks for a verti-
cal extension of all soil and waste pipes
through the roof. This extension affords
a ready outlet for all gases that would
otherwise tend to accumulate inside the
pipe system. In the case of soil pipes
nothing short of an extension the fidl
bore of the pipe will answer this purpose.

HOUSE DKAINAGE AM) SAMTAKY I'M MBING.

393

It has been proposed, of late, to enlarge
the soil pipe from the highest floor fco

the roof to six inches diameter, in order
Completely to prevent any stagnation of
air in the pipe. Waste pipes should be
enlarged from the point where they past
through the roof, to four inches diameter,
as smaller outlets are liable, in cold cli-
mates to become obstructed by the freez-
ing of condensed vapor. Plumbers some-
times use galvanized wrought iron or tin
pipes for this extension, but this is de-
cidedly bad practice. It should be of the
same material as the main soil pipe, and
its joints should be worked with equal
care.

The extension of soil and waste pipes
should terminate at a distance from any
windows, louvred skylights, or ventilating
flues, and at least two feet below the top
of the nearest chimney. It is desirable
to have this extension as high as possible
above the roof, so as well to expose the
mouth of pipe to the influence of air
currents. In order to prevent any ob-
struction of the soil pipe, plumbers often
cover the mouth with a return bend.
This, however, is objectionable, as it in-
terferes with proper ventilation. Less
bad is the plan of capping the soil pipe with
a suitable fixed cowl, such as, for instance,
Emerson's or Wolpert's ventilator. The
best plan seems to be to do away entirely
with any cover to the soil-pipe mouth.
Capt. Douglas Galton, in his book "Con-
struction of Healthy Dwellings," says in
regard to this question: "A tube or
shaft with an open top acts best. It is,
however, necessary to protect the top to
prevent rain from entering the tube; but
a cover tends more or less, according
to its shape, to delay the current in the
tube or shaft." This necessity of covering
ventilating tubes or chimney tops to pro-
tect them from rain, does not exist in the
case of soil pipes ; these may only want
protection against malicious introduction
of stones or similar articles. A galvan-
ized iron, copper or brass wire basket set
into the mouth of the soil pipe will an-
swer this purpose.

There is no doubt that open-mouthed
pipes have a better upward ventilation
than pipes covered with cowls, if the wind
blows horizontally or nearly so. Wolpert
in his "Treatise on Ventilation and
Heating " states the average useful effect
in per cents, of the velocity of the

wind, as derived from a number of ex-
periments, to be:

68.0 per cent for open-mouthed tubes,

51.0 per cent, for pipes capped with

Wolpert's new cowl,
35.8 per cent, for pipes capped with

Wolpert's old cowl,

for a horizontal direction of the wind. In
other words, the upward suction in a tube
without any cowl is in the average equiv-
alent to over | of the force of the wind,
blowing over it in a horizontal direction.
For pipes capped with Wolpert's new
cowl it is only a little more than £ of the
wind force, and for the old cowl it is J of
it. As an average for other directions of
the wind Wolpert finds the upward draft
in pipes covered with his new and old
cowls to be 51.5 per cent, and 34.5 per
cent., respectively, of the wind force.*

The result of an elaborate series of
about 100 experiments upon ventilating
cowls, made on seven different days, at
different times of the day, and under
different conditions of wind and temper-
ature, by Messrs. W. Eassie, Rogers Field
and Douglas Galton, was as follows:
"After comparing the cowls very care-
fully with each other, and all of them
with a plain open pipe as the simplest,
and in fact only available standard,
the sub-committee find that none of
the exhaust cowls cause a more rapid
current of air than prevails in an
open pipe under similar conditions, but
without any cowl fitted on it. The only
use of the cowls, therefore, appears to be
to exclude rain from the ventilating pipes ;
and as this can be done equally, if not
more efficiently, in other and similar ways,
without diminishing the rapidity of the
current in the open pipe, the sub-com-
mittee are unable to recommend the grant
of the medal of the Sanitary Institute of
Great Britain to any of the exhaust cowls
submitted to them for trial."

FRESH AIR INLET.

The second requirement calls for a fresh
air inlet or fresh air pipe. This is no less

♦The current of air in these experiments was
created by a powerful fan, the velocity of the current
varying from 8 to 31 meters per second (from 17.9 to
I 69.3 miles per hour), equivalent to high winds and hur-
ricanes respectively. The diameters of the cowls
tested varied from 0.787 to 3.937 inches. It is to be re-
gretted that the author did not extend his experiments
so as to include much smaller velocities of current.
It is very likely that for the latter the percentage of
useful effect of cowls would be much smaller.

394

VAN NOSTRAND'S ENGINEERING MAGAZINE.

important than the extension of the soil
pipes through the roof. In order to ef-
fect a constant movement and change of
air in the pipes, two openings are required,
an outlet and an inlet. The extension of
the soil pipe through the roof provides
only an escape for the foul air gener-
ated in the soil pipes and waste pipes
through the decomposition of foul or-
ganic matter, clinging to the interior of
pipes and lodging in traps under water
closets and fixtures. But in order to ox-
idize and thus render harmless this matter
undergoing putrefaction within the pipes,
a constant introduction of fresh air from
the outside atmosphere is necessary. As
the soil pipe is warmer in winter time
(being in the constantly heated house)
than the fresh air pipe, located outside of
it, an almost continuous upward current
in the soil pipe results. . In summer time
this current is only seldom reversed ; for
as a general rule, the top of soil pipe is
heated by the sun more than the fresh
air pipe near the ground.

There is a second and almost equally
important reason for providing a fresh
air inlet, wherever the third requirement,
the trapping of the drain, has been com-
plied with. If a water closet is used or a
pail emptied into a slop sink, the water
discharged into the soil pipe acts like a
piston ; although it is not likely to fill a
4-inch pipe, it certainly carries the air on
its course downward with it by friction.
Thus the descending water drives air be-
fore it and out through the fresh air pipe ;
if this had not been provided, it would
very likely force the nearest traps under
fixtures, and send a puff of sewer gas
into the living rooms. This reversed ac-
tion of the fresh air inlet does not occur
sufficiently often to warrant the appre-
hension of any danger in the location of
the inlet. Of course, it should not be
too near under windows of living rooms
or dormitories, nor should it be placed too
near the front steps of a city house. A
little judgment should be exercised in lo-
cating the fresh air inlet. In cities, hav-
ing between the house and the street a
wide parking, it is best to build in this a
small manhole, at the bottom of which
the trap and opening for fresh air are lo-
cated. The top of manhole should then
be closed with a cover, having numerous
openings so as to permit the outer air to
enter the drain freely, and also to pre-

vent as much as possible obstructions by
snow or ice in winter time. For this
reason it cannot be recommended to open
the fresh air pipe into a gully in the side-
walk, or in the floor of an area. Equally
objectionable is the location of the fresh
air pipe in a coal slide. It seems best to
carry the fresh air pipe some distance
away from the house, and this is always
practicable in the case of country houses,
where the fresh air pipe should prefera-
bly be hidden from view by shrubbery.

If the main trap is located inside the
foundation walls, the fresh air pipe should
enter the drain just above the trap by a
T or Y branch. Only in rare does cases
it become necessary to carry the fresh air
pipe vertically upward through the roof.
This plan would neither be very efficient,
as the difference in temperature of inlet
and outlet pipe would be small, nor very
economical.

As regards size of the fresh air pipe, I
would say that nothing short of the di-
ameter of the iron drain would answer ;
as this is generally 4 inches in diameter,
a 4-inch opening for fresh air pipe is re-
quired. This opening should be pro-
tected against obstructions by a wire
basket similar to that used for the upper
part of soil or waste pipes.

TKAP ON MAIN DKAIN.

Our third requirement calls for a trap
on the main drain between the sewer,
cesspool or flush tank, and the fresh air
pipe. A trap is practically a suitable
bend or dip in the drain, which retains a
sufficient quantity of water to prevent
the passage of sewer gas.

The opinions of experts as to the ad-
visability of trapping the main drain are
divided, some considering the trap nec-
essary, while others claim it should be
omitted.

The objections urged against the use
of traps are as follows:

1. They impede the ventilation of the pub-
lic sewers.

2. They form an obstruction to the flow of
the sewage in the house drain, and are, there-
fore, the cause of accumulations of foul mat-
ter in the drain, which by its decomposition
will generate noxious gases; also

3. Foul matters will lodge in the trap.

While the first objection does not
strictly belong to the subject of this paper
I will say that it is accepted by most

H0TJ8E DRAINAGE AM) SANITARY PLUMBING.

395

authorities that house drains and soil
pipes should not be used as ventilators for

tin I sewers. In exceptional cases

— such as, for instance, where; an entirely
new sewerage system is built, designed
and constructed according to uniform
plans, and where not only the construc-
tion of sewers, but also the house plumb-
ing is under constant supervision of the
engineer and designer of the system* —
the trap (and consequently the special
fresh air pipe) may, perhaps, be left out.
But I believe that a proper ventilation of
sewers can be effectually carried out with-
out ventilating through the houses.f

In regard to the second and third ob-
jections, I would say that obstructions do
not frequently occur if the drain is care-
fully laid, with sufficient and continuous
fall to insure a cleansing velocity of the
flow. If such an inclination cannot be giv-
en to the drain, proper flushing appliances
should be used, and these will by daily
or more frequent washings, insure the
removal of all matters liable to lodge in
the trap. Another most necessary pre-
caution to prevent accumulations in the
trap, where the fall is very slight, may be
found in the use of a proper grease trap,
about which I shall speak hereafter.

Xo amount of care in laying the drain
•will prevent its obstruction through care-
lessly introduced articles; these will
mostly lodge in the trap. A cleaning
hole should therefore be provided with
the trap, and is rarely omitted in good
work, or else a Y branch, closed with a
trap screw, should be inserted just a little
above the trap.

In Vol. III. of the "Sanitary Engi-
neer" will be found a discussion of the ad-
visability of trapping the main drain.
My own opinion, as stated in a commu-
nication to that journal, is as follows :

"If we could have ideal sewers, house
drains and soil pipes, it might, perhaps,
be possible to dispense with such a trap
altogether. But since all sewers may
have temporary stoppages from some
cause, since house drains may settle or
leak, and joints of soil pipes crack, thus
allowing sewage matter to undergo putre-

* For instance, at Memphis, Term., and at Hamburg,
Dantzic, Frank fort-on-Main, Berlin, Breslau, and other
places in Germany.

t See Mr. Edward S. Philbrick's articles on " Venti-
lation of Sewers," in the Sanitary Engineer, Vol. I.
See also Sanitary Engineer, Vol. V., Number 12, page
24G.

faction and enter the interior of houses,
I would in all cases advise the use of a
safeguard, consisting in a disconnecting
trap and a /cell ventilated 80il pipe. This
latter arrangement is a conditio sine qua
>h>n, and rather than have, a trap /"it/tout,
ventilation I would advise to have none

at all I would always

condemn as unsafe a system of house
drainage in which the public sewrers are

ventilated through the houses

The work of ventilating public sewers
should, in my opinion, be done by the
same public authorities who devise the
sewer system, and not by the house-
holders."

Leaving aside, however, the case of a
house drain connecting with a public
sewer, it seems quite evident that, in the
case of a house discharging its sewage
into a cesspool, an effective barrier should
be imposed to the gases constantly gen-
erated in that receiver of all foulness from
the household; and equally so in the
qase of a flush tank which temporarily
holds a large amount of faecal and other
refuse matter, which sometimes under-
goes decomposition.

The principle of disconnecting each
house from the street sewer was first ad-
vocated in England, and its importance
becomes most apparent in the case of an
epidemic, as by the use of a trap each
house will be isolated, while if all houses
have an open connection with a sewer,
this and the house drains may become the
channels for spreading the disease from
one house to another. It has been said
by those not in favor of such disconnec-
tion, that the air of the house drain, the
soil pipe and the branch wastes is much
worse than that of most city sewers, and
that consequently no harm could be done
by allowing the sewer to breathe through
the pipes in the house. Such statement
may be true in regard to the sewers of
some cities ; in others, sewers, especially
if built long ago, are extremely foul.
But it seems to me that just where the
air of drains and pipes is foul, it needs a
strong dilution and purification by
abundant fresh air, which an opening to
the outside atmosphere can furnish, but
never a direct connection with a sewer.

An open connection of the house drain
with a sewer or cesspool is necessarily
based upon the condition that every joint
in the house is perfectly tight, and every

396

van nostrand's engineering magazine.

trap perfectly trustworthy. As plumb-
ing is done in most bouses these condi-
tions are only seldom fulfilled. But even
where in new work such a standard of de-
sign and workmanship has been reached,
the work may not remain so forever.
It is, therefore, advisable to use a trap
on the main drain as a safeguard, but in
addition to this to insist upon occasional
inspections. These become a necessity in
the case of large buildings, such as
hotels, schools, large factories, jails and
almshouses.

Incidentally, it should be mentioned
that a trap on the drain performs a most
useful office during repairs or alterations
of the plumbing work in keeping from
the interior of the building the gases
from the sewer.

Much, of course, depends upon a
proper kind of trap for such disconnec-
tion. The old so-called " cess pool trap "
is, next to the pan closet and the D-
trap, the worst device ever proposed in
connection with house drainage. As usu-
ally constructed it is of very large size,
with square corners, and soon accumu-
lates filth, becoming in a short time in
reality a cesspool.

The common runnin'g trap, which is
manufactured in earthenware as well as
in iron is the simplest and at the same
time the best of all forms. It should
preferably have a vertical drop of a few
inches from the drain to the water line in
the trap in order to expel any solids that
would tend to lodge in it. The running
trap is often provided with a cleaning
and inspection hole at the house side of
the water seal, which serves as a fresh
air inlet, when the trap is placed in a
manhole outside of the house. In other
instances a rain leader is inserted into
the opening of the trap, which thus re-
ceives abundant flushing at each rain
fall. The running trap is sometimes
located on the line of the iron drain, just
inside of the foundation wall, so as to be
at all times easily accessible. A trap in
iron, with a cleaning hole and a cover is
then used. Care should be taken to close
the cover perfectly air-tight.

In all cases the trap should be so lo
cated as not to be liable to freeze in cold
climates or exposed localities.

In England various "disconnecting
traps " have been used, such as Moles-
worth's trap, Prof. Reynolds' and Dr.

Buchanan's disconnectors, Hellyer's
Triple-Dip Trap, Pott's Edinburgh " air-
chambered sewer trap," Stiff's "inter-
ceptor " sewer trap, Weaver's disconnect-
ing trap, Mansergh's, Buchan's, Banner's,
Stidder's, Bavin's traps, " Eureka " sewer
air trap, and many others. All of these
may have certain merits, but nothing
could be better nor cheaper than the
common running trap with fresh air pipe
used almost exclusively in American
plumbing.

For those exceptional localities where
undue pressure in the sewer, from wind
blowing into the outlet of the sewer, or
from sudden changes of temperature
(when exhaust steam is allowed to enter
a sewer), or from heavy accumulations of
surface waters gorging the sewer, or
from the action of the tide in tide-locked
sewers, frequently forces the seal of the
trap, two running traps with a proper
vent pipe between them have been rec-
ommended. I have myself, for some
time, advocated such an arrangement,
which, after further experience, I think
complicated and unnecessary. It would
require either a pipe extended through
the roof, between the two traps, or else
an open shaft (a manhole) between them,
and besides this, in every case, afresh-air
pipe entering the drain above the upper
trap.

TRAPPING OF FIXTURES.

The fourth essential, as stated above,
calls for a suitable trap, placed as near
as possible under every fixture.

As regards this point I cannot agree
with the views of Prof. Osborne Reynolds
of Owens College, Manchester. In his
otherwise excellent little book, " Sewer
Gas and how to keep it out of Houses,"
after explaining the necessity of a dis-
connecting trap on the main drain, and
giving particulars about its construction,
he continues : " There will then be no
need to have traps within the house!"

Traps under fixtures become a neces-
sity, as much of the so-called "sewer
gas " is actually generated in the drain
and soil pipes of the house. Even the
waste from a wash bowl becomes coated
in time with a soapy slime, emitting bad
odors. The trap on the main drain
would offer no protection against the
foul gases derived from organic matter
decomposing within the pipes. We thus

HOUSE DRAINAGE AND SANITARY PLUMBING.

397

see that, while some advocate the trap
on main drain, but no traps under fix-
tares, others leave out the main trap,
but trap the outlets of all fixtures. In
my opinion, both the trap on main drain
and those under fixtures are necessary.

Traps should be located as close as
ible to fixtures, in order to reduce the
length of waste pipe on the house side of
the trap, which is liable to become foul
with long use. Probably the best ma-
terial for traps is lead, as this permits of
making a good joint with the lead waste
pipes. As Mr. Hellyerhas truly pointed
out, the junction of the trap with the
waste pipe is of far more importance
than its junction with the fitting, because
the former is on the sewer side of the
trap, and, unless properly made, would
afford a passage for gases from the
waste pipe system into the rooms.

Whatever kind of trap may be used
under fittings (and there is an endless
number of such patented devices), it is
of the greatest importance that the trap
should be self-cleansing ; for this reason
traps with square corners or large j
spaces, liable to accumulate dirty matter, j
are objectionable. Much depends on a
proper size of traps for waste pipes : the
smaller the trap the better will it be
washed clean. As a good rule I would
recommend to choose a trap a quarter or
half an inch smaller than the diameter of \
the waste pipe, to which it is attached.
The flushing stream is thus concen-
trated, and its scouring power increased
within the trap, while on the other hand
a trap an inch larger than the waste pipe
is sure to fill up in time with sediment.

The following will serve as a guide :

Traps under water closets with 4 in. soil
pipe should be 3£ in. to 4 in. diameter.

Traps under wash basins with l£in. to 1\ in.
waste pipe should be 1 in. to \\ in. diameter.

Traps uuder bath and foot tubs with !U in.
waste pipe should 11 in. diameter.

Traps under btundr}' tubs with 11 in. to 2 in.
waste pipe should be 1£ in. to 1$ in. diameter.

Traps under sinks with 14 in. to 2 in. waste
pipe should be 1^ in. to H in- diameter.

Traps under slop siuks with 2 in. to 3 in.
waste pipes should be H hi- to 2 in. diameter.

As regards the proper dip of traps I
would say that traps under those fittings
which receive solids (water closets) should
not have a greater dip than \\ to 2
inches, because otherwise the solids are
not readily removed, and lodge in the

trap. For traps of minor wastes a larger
dip or ki water seal " is advantageous, as
affording a protection against loss of

seal through evaporation, siphonage or
back pressure.

Traps may be classified according to
the means used for the exclusion of gases
into :

1. Water-seal tr<ij>s.

2. Mechanical traps.

The characteristic of all water-seal
traps is that they have in their lowest
part a bulk of water divided by a dip in
the pipe, so as to stand on the house side
as well as on the sewer side one or sev-
eral inches higher than the lowest point
of the dip, thus making a seal which,
under ordinary circumstances, prevents
the passage of gases.

The traps of the second class have, in
addition to the water-seal, a mechanical
contrivance such as floats, balls, valves,
flaps, &c, to exclude sewer gas.

Of water-seal traps I mention the bell
trap, Antill's trap, the old fashioned D-
trap, the bottle or round trap, Adee's trap,
the Climax trap, the common S-trap, P-
trap and three quarter S-trap. There
is an endless variety of mechanical traps,
amongst which I mention Bower's trap,
Cudell's trap, Garland's trap, Buchan's
trap, Waring's check valve, Nicholson's
mercury seal trap, and others (see Fig.

2-)

The bell trap A is objectionable on ac-
count of insufficient water seal and im-
proper shape. It is frequently found at
the outlet of sinks and yard gullies, and
being in its upper part a movable strainer,
it is often lifted by servants or thought-
less persons, and the gases from the
drain pipe thus enter the house freely.

Antill's trap B avoids this defect, hav-
ing a fixed strainer, but is objectionable
on account of shape and small water-
seal.

The D-trap C and the bottle trap D
constitute small cesspools ; they violate
the principle tha£ a trap ought to be self-
cleansing. The D-trap accumulates dirt
and grease in the upper corner, which
receives no scouring from the water pass-
ing through the trap ; and the bottle
trap very often chokes up as shown at E.
A round trap of improved shape is shown
at F, which may keep cleaner on account
of its round bottom.

398

VAN NOSTEAND7S ENGINEERING MAGAZINE.

EOUSE DRAINAGE AM) SANITARY PU'MHING.

399

Adee's trap G is little better in this
respect, though it has this to recommend
it that it is not so easily siphoned, having
a large air space above the water, and a

largo body of water in 1 he trap. This is
also true of the round trap, when new
and clean ; when choked with grease as
shown at E. it is as much liable to siphon-
age as the S trap.

The Climax trap, H,has a large dip and
a round cup at it's bottom, which is re-
movable for cleaning purposes. Its re-
sistance to siphonage is not greater than
that of any of the other traps, or that o\'
the common S-trap with same depth of
water seal.

The P-trap I, and Strap J, are shaped
so as to be perfectly self- cleansing when
adapted in size to their waste pipes.
They are of uniform diameter through-
out, have no nooks or corners to accum-
ulate dirt. The old hand-made S-traps
with seams have been superseded by
lead traps cast in a mould such as the
Da Bois traps. As regards cleanliness
these traps are undoubtedly superior to
all other traps of which I have knowledge.
Tney cannot, however, be relied upon to
exclude sewer gas, as their water-seal is
frequently destroyed either by siphonage
or by evaporation. They are shown in
Fig. 2, with a vent pipe attached at the
highest bend of the trap on the sewer
side of the seal. The object of this vent
pipe is to prevent siphonage, as will be
explained hereafter.

Bower's trap is shown at K. This trap
has a water-chamber into which the pipe
from fitting enters at the center, and an
outlet pipe on one side. The mouth of
the inlet pipe is sealed by the water in
the chamber, but in addition to this a
floating ball of india-rubber in the water
chamber is held tightly against the
mouth of the inlet pipe, forming a seal,
which, however, depends on the quantity
of water in the chamber. The water, in
passing through this trap, removes the
ball from its seat and rotates the same,
thus keeping it clean and free from mat-
ters adhering to it. An additional ad-
vantage of this trap lies in the ball, which,
being compressible, allows the water in the
chamber to freeze without danger of the
bursting of the cup. Unless the soil pipe
is extended full size through the roof
this trap may have its water lowered by
siphonage so much that the ball will

drop from the mouth of the inlet pipe,
but with proper ventilation of soil and
waste pipes it forms an efficient trap for

wash bowls, tubs and sinks, although it is
not as self-cleansing as the common
S-trap.

Waring's check-valve is shown at O.
This valve forms a seal by its weight,
and the seal is dependent upon the ac-
curacy of the turned seat. Hair and
particles of other matters may adhere to
it and prevent a tight shutting of the
valve.

C udell's trap L and Buchan's trap M are
constructed much upon the same princi-
ple, but have a heavy metallic ball instead
of a conical-shaped valve. This ball may
keep cleaner by being revolved, but in
this case, as above, the tightness of the
seal will depend upon the accuracy of
turning the seat.

Nicholson's mercury seal trap N has
an inverted porcelain cup inside of its
cylinder, the edge of which rests on mer-
cury, forming a tight seal. The cup is
lifted, at each discharge, by the force of
the water entering at bottom of cylinder;
after all water has passed from the basin
the cup falls back in its place. This trap
is generally made of earthenware with
brass couplings ; it is therefore a more
expensive trap, but the mercury seal very
efficiently prevents the entrance of sewer
air, even if the water in the cylinder
should be removed by siphonage or evap-
oration.

VENTING OF TRAPS.

The fifth requirement asks for a proper
vent pipe for such traps under fixtures as
are liable to be siphoned. This siphon-
age constitutes in many cases a danger,
but especially so with S-traps. Traps
may be siphoned under the following con-
ditions :

1. Traps with an easy bend, on a
rather steep line of waste pipe, and with
small depth of seal, are liable to empty
themselves by the momentum of the water
rushing from the fitting through them.
The air in the upper bend of the trap is
expelled and replaced by water, which
causes the trap to act as a siphon. When
the fitting has discharged all its water,
and air breaks the siphon, the water in its
inner limb will mostly drop back into
the trap, but in case of a small dip it
would be insufficient to seal the trap.

400

VAN NOSTRAND7S ENGINEERING MAGAZINE.

Unless a slow after-flush takes place the
trap remains unsealed.

2. Traps under fixtures may be si-
phoned by a flow of water coming from
another fitting on the same branch waste
pipe.

3. Traps may be siphoned by a dis-
charge— from a water closet, a tub, or
from a pail of water from a slop sink —
into the main soil pipe, to which the
branch waste of the trap is connected.

To guard against the first danger the
dip or water seal of the trap should be
as great as possible; but, even then a
special vent pipe will often be necessary,
attached to the highest part of the bend
in the trap on the sewer side of the water-
seal, or else a mechanical trap should be
used.

To guard against the second danger
the trap of each fixture should be vented ;
wherever possible, each fixture should
discharge independently into the soil
pipe, thus reducing the danger from
siphonage to cases 1 and 3.

The third danger from siphonage by a
discharge into the main soil pipe, either
above or below the point where the waste
from the trap enters it, will in some cases
be sufficiently prevented by the complete
and thorough ventilation of the soil pipe.
In many cases, however, the venting of
the trap becomes necessary.

Where a number of water closets dis-
charge into the same inclined branch of a
soil pipe the air-vent to the water closet
trap becomes necessary, especially so with
water closets, discharging quickly a large
body of water, such as the various pat-
terns of the plunger closets (Zane, Dem-
arest, Jennings) and some of the " wash-
out " closets.

Where slop hoppers are trapped by an
S trap, this must be properly guarded
against siphonage, as the trap is very
likely to lose its seal from the momentum
of the water rushing through it each time
a pail of slops is quickly emptied into the
sink.

The material most suitable for air pipes
is lead, as such pipes are easily joined to
lead traps. Sometimes wrought-iron
tubing is used, and, since the vent pipe is
not so much intended for carrying off foul
gases [which office is performed by the ver-
tical extension of all waste pipes through
the roof] as to afford a passage to air in
order to break the suction, they may be

safely used. Care should be taken to lay
these pipes with a slight inclination, in
order to prevent accumulation of water
from condensation in the pipes. Vent
pipes for fixtures on different floors may
be joined, if convenient, and may enter the
soil pipe above the highest fixture. But
it is preferable to run them to a main
vent pipe of lead, or better, cast iron,
which goes through the roof independ-
ently. Where this passes through the
roof it must be enlarged to 4 inches diam-
eter, as it might otherwise be obstructed
by ice in winter time. It should not be
covered at the top with any kind of ven-
tilator. The size of the vent pipe should
never be less than that of the trap, except
for water closet traps, where it should
be 2 inches in diameter, but in the case
of two or more water closets it should be
3 inches and sometimes even larger from
the point where the various vent pipes
join.

It is often not only costly but also in-
convenient to run vent pipes to the roof.

There is also some danger that the vent
pipes for traps under tubs, sinks and
bowls may stop up with soapsuds or
grease, in which case they would cease to
act properly. The continuous current of
air in the vent pipe, in passing over the
water in the trap, will tend to increase
its evaporation. Finally it becomes nec-
essary in the case of high buildings,
largely to increase the diameter of vent
pipe in order to make up for the loss
through friction necessarily occurring
with long air pipes. Therefore, while I
consider vent pipes for traps a necessary
evil in many cases, I am inclined, in other
cases, to prefer a good mechanical trap,
which cannot be siphoned, provided the
soil and waste pipe system has ample
ventilation. Such mechanical trap may
be used under sinks, tubs and bowls ;
but for water closets and slop hoppers
(if without a strainer) the simple lead
water seal trap with vent attached is the
only safe device.

EVAPORATION OF WATEE IN TRAPS.

Nothing short of continuous use of the
fixtures will prevent evaporation of the
water in traps. A large dip is recom-
mended for traps on waste pipes to guard
against a rapid loss of the seal. When
a house will be left unoccupied for a long
time, but especially during the hot sum-

HOUSE DRAIN Ad K AND SANITARY PLUMBING.

401

mer months special precautions should
be taken to prevent sewer gas from en-
tering the rooms and saturating carpets,
wall-paper and furniture. Replacing the
water in traps with oil or glycerine may
be recommended, or else the use of com-
mon rock salt which attracts sufficient
moisture from the atmosphere to make
up for the loss by evaporation.

UPTION OF GASES BY THE WATER IN TRAPS.

It is well known that water has the
property of absorbing gases, and it was
believed that the water in traps would
readily absorb sewer air from the soil
pipe and give it off at the house side of
the trap by evaporation. It has also
been asserted that microscopic organisms
(germs of disease) floating in gases of
y would pass through the dip of the
water-seal and enter the house through
the fixtures, and that consequently the
water-seal of traps offered no security
against the invasion of sewer gas. Dr.
Fergus, of Glasgow, Scotland, was the
first to call attention to this matter, and
made an extensive series of experiments
in 1873-74, which led him to condemn
as unsafe the system of water carriage in
general, and the trapping of fixtures.
The views of sanitarians, based upon Dr.
Fergus' experiments, have been much
modified by recent experiments of Dr.
Carmichael, of Glasgow, by researches of
Dr. Frankland in London, Wernich and
_;eli in Germany, Prof. Rafael Pum-
pelly and Prof. Smyth in Newport, R. I.,
and others.

Dr. Fergus' experiments were made
with gases in a concentrated condition, and
as such are quite as reliable as the more !
recent experiments. But the latter more |
closely resemble actual cases, being made
by experimenting directly with soil pipe
gases. Referring to what has been said !
about sewer gas, it will be seen that am- !
monia, sulphuretted hydrogen and other
gases of decay are present in drains and
soil pipes only in minute quantities. Dr.
Carmichael found that the amount of
these gases passing through a water-seal
trap was so extremely small that no dan-
ger could be apprehended. With a thor-
oughly ventilated system of soil and waste
pipes this peril may be taken as insignifi-
cant.

Another set of experiments by Dr. Car-
michael, made to determine the passage
Vol. XXVII— No. 5—28.

of germs through water, seems to indi-
cate that germs, even if contained in the
water of traps, are not liberated from it,
as was hitherto supposed, unless the water
is violently agitated. Frankland in Eng-
land, Naegeli in Germany and Prof. Pum-
pelly in Newport, It. I., arrived at the
same conclusion, after careful investiga-
tions and experiments.

Dr. Carmichael sums up his conclu-
sions by saying : " Water traps are,
therefore, for the purpose for which they
are employed, that is, for the exclusion
from houses of injurious substances con-
tained in the soil pipe, perfectly trust-
worthy. They exclude the soil pipe at-
mosphere to such an extent that what es-
capes through the water is so little in
amount, and so purified by filtration, as
to be perfectly harmless ; and they ex-
clude entirely all germs and particles,
including, without doubt, the specific

germs or contagia of disease "

Further scientific researches will un-
doubtedly throw more light on this yet
little investigated subject.

TRAPS FORCED BY BACK PRESSURE.

It has already been explained how traps
under fixtures may be forced by back
pressure. This cannot, however, occur
with traps under fixtures, if all soil and
waste pipes are properly extended through
the roof, and provided with a fresh air
opening at their foot.

BRANCH WASTES FROM FIXTURES.

Fixtures are connected to the soil and
waste pipe system by branch wastes car-
ried under the floors. The material used
almost exclusively for such branch wastes
is lead, and the sizes adapted to different
fixtures have already been stated. The
connection is very simple in the case of
a single fixture, such as a kitchen sink,
or a lavatory. The problem becomes
more intricate in the case of a set of
fixtures, such as are generally located in
a bath or dressing room. A bath room
of the better class of city houses contains
a water closet, a bath tub, and a lavatory,
sometimes also a hip-bath or bidet. It
is. desirable that each of these fixtures
should have a separate connection to the
soil pipe. Such is seldom possible, ex-
cept when the soil pipe is located in a
.special shaft, or where it is possible to
conceal the pipe and Y branches by a

402

VAN nostrand's engineering magazine.

" false ceiling," as the height of timbers
does not generally allow of the placing
of more than one Y branch.

A very common, but most defective
manner of overcoming the difficulty is by
emptying the wastes of bath tub and
bowl into the water closet trap below its
water line, supposing the water closet to
be of such type as requires a lead trap be-
low the floor. As the waste pipes have
only a slight fall to the trap, the water
of the latter, which frequently holds ex-
cremental matter, will stand for a long
distance back in the waste pipe and keep
it continually foul ; the free flow from
the bath and bowl is much retarded, the
waste being air bound between the water
closet trap and the traps of bowl and
bath. Matters are even worse, when the
water closet trap is meant to serve also as
trap for the bowl and bath, these having
no traps placed under them. The foul
water standing back in the waste pipes
will then readily evaporate into the dress-
ing room, and fill it with noxious odors.
Moreover, it frequently happens that this
trap becomes displaced by tipping over,
or that the waste pipe attached to the
trap sags, so as to render the water seal,
which is rarely over an inch in depth, in-
effective. It will be readily understood
how, under such circumstances, the foul
gases of the soil pipe — especially if this
be unventilated, as is so often found in
examining old houses — gain an easy ac-
cess into our rooms. Should the main
drain have an untrapped connection to a
sewer or cesspool, the gases from these
would ascend and permeate the whole
building. Such instances of faulty work
are by no means rare, and are causes of
much preventible headache and sickness.

To run such wastes into the water closet
trap above its water line is equally wrong.
Where the water closet is some distance
away from the soil pipe, it is possible to
insert between its trap and the junction
with the soil pipe, on the horizontal part
of the soil pipe, two 4" X 2" Y branches,
or else one double Y branch for bath
and bowl wastes. Where the water closet
is quite near the soil pipe, and the con-
necting pipe between them is of lead, the
wastes from bowl and bath may join the
latter beyond the trap. Wherever there
is room enough, a 4" X 2" double Y
branch may be inserted vertically below
the water closet branch on the soil pipe,

or else one 4"x 2" Y for bowl above
the water closet branch, and a 4" X 2" Y
below it for the bath waste. It seems
desirable that the iron works should
manufacture a combined Y branch, having
a 4-inch opening for the water closet
waste, and one or two lj-to2 inch open-
ings for the smaller wastes.

Long lengths of waste pipes under
floors are objectionable; to avoid them it
is sometimes better to provide a special
stack of 1 J to 2 inch vertical iron waste
pipe near lavatories or baths, where these
are remote from the main soil pipe.

It is customary to provide bath tubs,
wash bowls, and pantry sinks with an
overflow pipe, in order to prevent flood-
ing of floors, if the outlet of any of these
fixtures should be closed by a plug, and
the water carelessly left running. These
overflow pipes should enter the waste
between the fixture and its trap, or else
they should enter the trap below the
water line, so that the trap serves for both
waste and overflow. Overflow pipes do
not receive a thorough flushing, and are
liable to become foul with soapsuds,
emitting unpleasant odors. For baths,
fortunately, the overflow pipe can be
safely dispensed with by using the stand-
ing overflow, for bowls those with " pat-
ent overflow," i.e., a concealed channel in
the earthenware bowl, have the length of
overflow reduced to a minimum.

A set of laundry trays is generally
trapped by only one trap, thus leaving a
long length of waste pipe in connection
with the air of the room. I believe, how-
ever, that such wastes, properly restricted
in size, and laid with sufficient inclina-
tion, can be kept well flushed and clean,
and therefore unobjectionable.

In the case of a set of water closets or
urinals I consider it imperative to have a
separate trap under each fixture.

It is of the utmost importance that the
connection between water closet and soil
pipe' should be absolutely tight. The
different types of water closets are pro-
vided at their outlets either with a lead
trap under the floor, or else they have a
trap of iron or earthenware, as the case
may be, above the floor, or they are so-
called " trapless " closets, in which case
the only water-seal against gases is
formed by the water held in the bowl
(either by a valve, pan or plunger, or by
a special shape of the bowl). For water

HOUSE DRAINAGE AND SANITARY PLUMBING.

403

closets haying a lead trap under the floor
a brass ferrule is connected by a wiped
joint to the end of the trap, and the fer-
rule is inserted into the hub of the iron

soil pipe, and caulked tightly. Thehonse
end of the lead trap is flanged out, and the

earthenware or iron horn of closet insert-
ed into it, resting with its horizontal
flange upon a ring of soft india-rubber,
or of oakum, saturated with red lead.
Wood screws, drawn through the hori-
zontal flange into the floor, tighten the
connection.

In the case of trapless closets and such
with trap above the floor, the outlet is

Derail? connected by a lead thimble to
the soil pipe in the same manner as just
described for lead traps.

Such a connection is in neither case a
perfect one. But in the case of closets
with trap under the floor, this connection
is on the house side of the trap, and the
danger from leakage of sewer gas from
the soil pipe is prevented by the water
seal. With trapless closets (such as
some pan closets, valve closets and
plunger closets), with closets having
trap above floor (short hopper, some
plunger closets), and finally with all
'; washout " closets such a connection is
dangerous, and a better joint than is
used at present should be devised, such

. for instance, a connection by means
of a brass ferrule between water closet
outlet and iron soil pipe.

SAFE-WASTES.

In order to prevent the flooding of
floors and ceilings, fixtures, such as
wash bowls, bath tubs, water closets, etc.,
are mostly lined with a safe of sheet
lead, provided with a waste pipe. In
bad plumbing work these " drip pipes "
are either joined into the nearest soil or
waste pipe — often even without a trap —
or else, in the case of water closet safes,
are made to run into the water closet trap.
Such drip pipes should not be connected
at all to the drainage system. They
should run vertically downward to the
cellar, and open either over a sink, or
terminate at the cellar ceiling. Should
it be feared that the drip pipes might
become the channels for leading the cel-
lar air into the upper rooms, their mouths
should be closed with paper, glued over
them, or the pipes should have an up-

ward bend, closed by a ball, which is
prevented from dropping by wire bunds.

RAIN LEADERS.

Rain-water pipes may be of galvanized
wrought-iron, or of tin; when laid inside
of a house they should be of oast iron
and their joints treated in all respects as
those of soil pipes. Before joining the
house drain they should be trapped, if
such junction is made beyond the main
running trap of the drain, and the trap
of the leaders should be sufficiently deep
in the ground to prevent the water from
freezing. If rain leaders join the drain
inside of the house they should not have
a special trap, unless their top opens
near dormitory windows. Sometimes a
leader delivers into the main trap of the
drain, and thus helps to cleanse the trap.

Bain leaders should never be used as
soil pipes nor should they be solely de-
pended upon to ventilate the drain ; and,
on the other hand, soil pipes should
never be used to carry rain water from
the roof.

In making a sanitary examination of
the Executive Mansion at Washington,
under direction of Col. Geo. E. Waring,
Jr., the writer had occasion to see an in-
stance of the violation of this rule. The
main soil pipe in the building was a 10-
inch (!) cast iron pipe, which served the
double purpose of receiving the discharge
from three water closets, a urinal, a slop
sink and some wash bowls and bath tubs,
and also all the rain water from the large
roof. At each rain-fall this large pipe
received ample flushing, but in times of
prolonged droughts its inner walls be-
came thoroughly slimed and foul wTith
excremental and other matter. In times
of violent rain storms the water rush-
ing down the 10-inch pipe and passing
the branch wrastes, very likely siphoned
all water out of the traps, thus leaving
the house unprotected against the foul
gases of the soil pipe.

CISTERN OVERFLOW PIPES.

Both under-ground cisterns and cis-
terns in the attic of a house should be
provided with an overflow. The usual
custom has been to connect this overflow
pipe to the drain, or, if inside a house, to
the soil pipe. In consequence of this
most pernicious practice the water was
contaminated, and since water is known

404

van nostkand's engtneeking magazine.

to be a carrier of disease germs not less
so than the air, sickness and deaths were
traced to this faulty arrangement.

No overflow from a cistern for cooking,
washing or drinking water should be con-
nected to any part of the drainage sys-
tem under any circumstances. Even if
properly trapped the danger is not re-
moved, as the water in this trap evapo-
rates, and as an overflow seldom occurs,
no water refills the trap, and drain air
passes freely into the tank. This over-
flow should be made to run into the gut-
ter of the roof, wherever this is practica-
ble. In cold climates or in exposed
places its outlet should be protected by
a flap-valve. If, for some reason, the
above course cannot be followed, the
overflow should discharge over an open
sink in the basement or cellar. If the
cistern is located outside of the house, the
overflow should be carried to some low
point, where it should have an open out-
let. Blow-offs for water-tanks should be
treated similarly to the overflow-pipe.

REFRIGERATOR WASTES.

It is not safe to have a direct connec-
tion between a refrigerator waste and
drain or soil pipes, for reasons given
above for overflows of cisterns. Small
refrigerators may waste into a pail to be
removed and emptied periodically.
Wastes from large refrigerators should
empty over an open cup with a waste at
its bottom, provided with a reliable
mechanical trap and connected to the
nearest soil pipe or drain.

DRAINAGE OF CELLARS.

It remains to discuss the proper
method of removal of excessive moisture
from the soil under and around a dwell-
ing. Unless this is properly attended to,
cellars of houses will be continually
damp, the brick or stone walls will
readily absorb the moisture by capillary
attraction and an excess of watery vapor
will fill the house. The well known re-
searches of Dr. Bowditch of Massachu-
setts, and of Dr. Buchanan in England,
have clearly established the relation of
excessive soil moisture to certain diseases,
notably consumption, bronchitis, pneu-
monia and other diseases of the lungs.

Dr. Parkes, in his admirable "Manual
of Practical Hygiene " speaks about
diseases connected with moisture and

ground-water as follows : " Dampness of
soil may presumably affect health in two
ways — (1) by the effect of the water, per
se, causing a cold soil, a misty air, and a
tendency in persons living on such a soil
to catarrh and rheumatism ; and (2) by
aiding the evolution of organic emana-
tions. The decomposition which goes
on in the soil is owing to four factors,
viz.: presence of decomposable organic
matters (animal or vegetable), heat, air
and moisture. These emanations are at
present known only by their effects ; they
may be mere chemical agencies, but more
probably they are low forms of life which
grow and propagate in these conditions.
At any rate, moisture appears to be an
essential element in their production.
The ground-water is presumed to affect
health by rendering the soil above it
moist, either by evaporation or capillary
attraction, or by alternate wettings and
dryings. A moist soil is cold, and is
generally believed to predispose to rheu-
matism, catarrh and neuralgia. It is a
matter of general experience that most
persons feel healthier on a dry soil."

In order to keep the level of the sub-
soil water below a certain depth artificial
channels should be provided, laid at that
depth and sloping towards some proper
outlet which will remove all surplus
water. These channels, which carry off
only clean water, are also called drains
(this being the original meaning of the
word).

Under the foundation walls of the
house trenches dug for this purpose
should be filled with loose or broken
stones. Drains (common tiles) should
be placed two or three feet below and
under the cellar floor, with open joints,
care being taken to prevent any intrusion
of earth at the joints, by wrapping tarred
paper or strips of cotton around them.
The drain can then be covered up and
buried. The size of the tile drain's will
depend on the character of the soil. As
a general rule 1^-inch tiles are quite suf-
ficient, except in the case of a spring in
the cellar, when it may be necessary to
use pipes of 2 inches and sometimes even
larger sizes.

The only difficulty, from a sanitary
j point of view, consists in finding a proper
| outlet. If the house is a country resi-
dence with ample ground around it, and
I especially if the land is not level, but

BOUflE DRAINAGE AND SANITARY PLUMBING.

405

slopes to some distant valley or creek, it
is very easy to continue the main cellar
drain with a sufficient pitch to some gut-
ter or open ditch, into which it may dis-
charge.

The case becomes difficult with city
houses, on narrow lots, with no other
outlet available but the sewer under the
street. A direct connection between the
cellar drain and the sewer is forbidden
for well-known reasons, and even the
interposition of a water-seal trap may
not be regarded as a sufficient safeguard,
for during periods of droughts the water
evaporates, allowing the gases from the
sewer to pollute the ground under the
house.

The drain should run into a mason's
trap with deep water-seal, and filled with
coarse sand or line gravel, and before
joining the sewer the drain should be
trapped by a running trap, into which,
if practicable, a leader should discharge.
Another arrangement is to trap the cellar
drain, and to provide an outlet for gases
which may force the trap, by a vertical
pipe, on the house side of the trap, and
opening on the surface of the ground.
This is sometimes done when the sewer
is in an alley at the rear of the house,
and an open yard gully may be con-
nected to the vertical vent pipe to supply
the running trap with water.

It is equally important to have a dry,
impervious floor in the cellar, which can
be secured by first laying a base of con-
crete, upon which a layer of about J inch
of asphaltum should be placed. This
makes the floor practically impervious.
It should then be properly finished with
a layer of best Portland cement.

DAMPNESS OF WALLS.

In order to prevent dampness of walls,
that part of the wall below the level of
the ground should be constructed with par-
ticular care. Nothing will better prevent
dampness in walls than a " damp course "
of some impervious material. Asphaltmn
is probably best for this purpose, though
layers of slate in concrete or damp proof
tiles are very efficient. If at all practi-
cable there should be a dry area all around
the foundation walls in order to prevent
any dampness in the walls originating
from the earth surrounding it at the
sides. If such an area cannot be provided

a double wall with an air-space between
inner and outer walls should be used.

SYSTEM OF HOUSE DRAINAGE.

Fig. 3 represents a section through
a dwelling house, illustrating the essen-
tial elements of a system of house drain-
age.

A is the gravel trap, into which the
subsoil drain B discharges, and which
serves to prevent the gases from the
sewer from entering the drain tiles and per-
meating the cellar. The drain B for cellar
drainage should be of common 1^-2 inch
tile drains, laid with open joints, around
which tarred paper or cotton rags may
be wrapped to prevent any stoppage of
the tiles from dirt falling in at the
joints.

C is the house drain, which should con-
sist of 4-inch vitrified pipe with well ce-
mented joints to within 10 feet from the
cellar wall. D is the running trap on the
main drain to disconnect the house from
the sewer. Into it the rain leader X dis-
charges. E is a Y branch, closed with a
brass trap screw, for cleaning purposes.
F is a fresh air pipe, 4 inches in diameter,
entering the house drain above the trap,
and carried some distance away from the
house, its mouth being hidden from view
by shrubbery, and covered with a wire
basket for protection against obstruc-
tions.

G is the 4-inch house drain, of heavy
iron pipe, with well caulked lead joints,
carried with sufficient fall along the cel-
lar wall to the furthest point, where it
receives either a soil pipe or a rain
leader.

H H are the 4-inch iron soil pipes,
which join the iron drain in cellar by Y
branches and eighth bends. They are ex-
tended full size through the roof, and
their outlets I I are protected by a
strong wire basket.

J is a small refrigerator which wastes
into a movable pail. K is the large tank
in attic, which is supplied through a ball-
cock from street pressure. Its overflow
pipe L is shown trapped by an S-trap
with deep seal, and emptying into the
gutter of the roof. The blow-off N
from tank runs down vertically and de-
livers over the kitchen sink.

M M are small cisterns for flushing the
water closets and slop hopper only.

406

TAN NOSTRAND's ENGINEERING MAGAZINE.

Fio\ 3-

r K

SYSTEM OF HOUSE DRAINAGE.

O O are earthenware wash bowls with
l^-inch waste pipes and overflow pipes of
lead, trapped by Cudell's or Bower's
traps, and delivering into 4" x 2" Y
branches of soil pipes.

P is a pantry sink, of heavy, tinned and

planished copper, with overflow and 1J"
waste pipe of lead trapped by a Bower's
trap and entering a Y branch of soil pipe.
Q are cement stone or ceramic wash
tubs, with \\" waste pipe, and trapped
by a Bower's trap.

BOUSE DRAINAGE AND SANITARY PLUMBING.

407

. li is an all earthenware flushing-rim
slop hopper, trapped by a vented S-trap,
ami flashed from a special cistern.

S is the kitchen sink, of galvanized or
enamelled iron, or of earthenware, trapped
by an 1J" Bower's trap with 1£" lead
waste pipe.

T is a hath tub, of enamelled iron,
or heavy planished copper or of porce-
lain. It is provided with a standing
waste, and trapped by an 1J" Cudell
running trap. T' is a small hip bath, of
copper, provided with overflow and 14"
waste pipe, trapped by a vented S-trap.

V is a 2-inch air pipe to prevent the
siphonage of traps. It is extended
through roof, and enlarged to a 4-inch
outlet, which should be left without any
other covering than a wire basket. Into
this air pipe enter the vent pipes from S-
traps under slop hopper, water closet and
hip bath.

W W W are water closets, the types
shown being the long and short hopper
and the washout closets. Each of these
is provided w7ith a special flushing cistern
M M M.

X X is a rain leader delivering the
water into the running trap of the house
drain.

Y is the blow-off from the boiler, which
wastes into a Y branch of the iron drain
in cellar.

The system described and illustrated
differs from the methods of house drain-
age as practiced in England in one essen-
tial point. There, it. is the rule to keep
soil pipes separate from waste pipes, to de-
liver to the former, in the words of Prof.
Fleming Jenkin, " such foul matters as
would certainly be tainted when conta-
gious disease occurs in the house," in
other words, the waste water from water
closets, urinals, slop sinks and probably
laundry tubs ; a second system " receives
all liquids, which may be called dirty,
but not foul — the water from baths, kit-
chen sinks, and wash hand basins." It is,
moreover, the rule in England to locate
the soil pij>e outside of the house walls,
and to deliver the waste pipes over an
open gully in the yard, from whence the
wastes run into the house drain. Both
arrangements are entirely impracticable
in this country on account of the severity
of the climate, and the separation of the
two systems by discriminating between

foul and dirty waste water leads to un-
necessary complications. With well joint-
ed, thoroughly ventilated soil pipes of
iron, it seems quite permissible in Ameri-
can plumbing to run into them the wastes
from any fixture in the house, if it be
near the soil pipe, and where vertical
stacks of wraste pipes are mil for bath
tubs and wash basins, these waste pipes,
if properly jointed, may with perfect
safety deliver into the iron cellar drain,
which receives the soil pipes of the
house.

If all the given rules are carefully ob-
served, the system of drainage of a dwell-
ing will be as perfectly as possible in ac-
cordance with the present knowledge of
sanitary science. Time and experience
may find out hitherto unknown faults,
but will also, it is believed, teach the
proper remedy. With p)ipes of proper
material, properly joined, properly laid,
and properly and sufficiently often flushed
with air and water, the object of a system
of house drainage seems to be attained,
viz., the instant removal from the house
of all liquid and semi-liquid waste mat-
ter, and the perfect oxidation and con-
stant dilution of the air contained in the
pipes.

Says Mr. J. C. Bayles : " The conclu-
sion I have reached is that when sewer
gas finds its way into a house through
the soil and waste pipes, the fault lies
somewhere between the architect, the
builder and the plumber. In any case,
it is without excuse. I know that houses
can be drained into sewers — without
bringing sewer gas into them. The exist-
ence of foul sewers is in itself a perpetual
danger to the public health, but there is
no reason why we should bring that dan-
ger into our houses by providing channels
through which the poisonous air of the
sewer can find a means of ingress. I
know of houses into which no sewer gas
ever comes — unless, possibly, through
the windows, borne in with the air of the
street — and I have no hesitation in say-
ing that, when the tenants of houses de-
mand immunity from the dangers of
unhealthful conditions, architects and
builders will find a means of correcting
the evils now complained of as practically
irremediable. Sanitary reform in cities
only waits until those to be benefited by
it shall demand it."

408

VAN NOSTRANITS ENGINEERING MAGAZINE.

RECORD AND PLAN OF DRAINAGE AND PLUMB-
ING INSPECTION.

It cannot be too strongly recommended
to every householder to keep for future
reference, for cases of inspection or repairs
and alterations, a complete plan of all tha
drain, soil and waste pipes in and outside
of the house, a record of the depth of
the drain, fof the sizes and material of
pipes, of the location of junctions, traps,
fresh air pipes, access pipes or cleaning
Y's, of all fixtures on every floor, etc.

Frequent inspections of the plumbing
of buildings are by no means superfluous.
They are very important in the case of
public buildings, schools, hospitals, asy-
lums, jails, hotels, but especially so, for
such buildings as are occupied only a
part of the year (summer residences,
seaside hotels, mountain resorts, etc.).
In some cities " sanitary associations "
have been organized, such as at Newport,
R. I., Lynn, Mass., Brooklyn, N. Y., and
other places. The members of these as-
sociations can avail themselves of the
services of an inspector of plumbing em-
ployed by the association, in order to as-
sure themselves by frequent inspections
of the sanitary condition of the plumbing
in the house, of its outside drainage and
water supply, its ventilation, etc.

In the case of new buildings the archi-
tect's plans should show the exact loca-
tion of the proposed plumbing work in
the house. The work should be done ac-
cording to written specifications, carefully
drawn up by the architect or a sanitary
engineer, under whose immediate direc-
tion the plumber should work. It is a mis-
take — but, alas ! how often is it made —
to give the plumbing work of a new build-
ing out by contract. The slight amount
saved in first expense is almost always
followed by an increased outlay for re-
pairing and altering defects, which appear
only after the house is occupied. A pru-
dent house owner will prefer to have his
plumbing done by day labor, by honest,
conscientious plumbers — and these are
by no means rare, as the universal cry
against them would seem to indicate —
who care more about their reputation
than about a few dollars earned through

dishonest and reckless work.

PLUMBING REGULATIONS.

The cities of New York, Brooklyn and
Washington lately have set an example

worthy of imitation in other cities.
The health authorities have issued ex-
cellent regulations for plumbing of
buildings, and require the plans for
plumbing to be submitted to them for
approval and for filing. The plumbing,
before being covered up, is examined
by intelligent inspectors of the Board of
Health. There may be at first some
bad feeling about such a measure, but
the good plumber will soon understand
that the law passed is to his advantage ;
it will protect him against the " botchers"
in the trade, and will help to re-establish
his of late much abused good name.

These plumbing regulations will cer-
tainly tend to lessen the frequent com-
plaint about bad plumbing in houses,
and the consequent entrance of sewer
gas. They will contribute much to-
wards the lowering of a high death rate,
and similar regulations may be adopted
with advantage in all large cities.

The Russian Arsenals. — The produc-
tion of the various Russian arsenals and
gun factories during the year 1880 was
as follows : The gun factory of Toula
turned out. 135,000 infantry rifles, and
15,000 cavalry carbines. That of Ses-
troretzk 120,000 rifles and 5000 Cos-
sack carbines. The Tjer workshops sup-
plied 130,000 rifles, 5000 Cossack carbines,
and 125,000 gun-barrels. The private
factory at Zlatwost furnished 15,833
swords and 25,000 gun-barrels, and
actions were purchased from the Obouk-
hov Steel Works. The arsenal at St.
Petersburg completed 150 short bronze
24-pounder guns, and supplied the breech-
blocks for 435 steel guns, which were
manufactured at the Oboukhov works ; 50
6-in bronze mortars were constructed at
Biransk. The different arsenals also de-
livered 270 iron field gun carriages and
wheels, 648 iron limbers, with wheels ahd
ammunition boxes, 378 ammunition wag-
ons, 20 siege gun carriages, together with
a large quantity of wheels and extra fit-
tings ; 2500 tons of powder were pro-
duced at the factories of Okhta, Chostka,
and Kazan ; 151 millions of cartridges, a
large quantity of caps, &c, were com-
pleted at St. Petersburg ; and the rocket
factory at Nicolaiev turned out about
5000 rockets of various kinds.

VENTILATION OF BKWERS.

4(>9

VENTILATION OF SEWERS.

I'mra "The Architect.'

A report has been prepared by Sir
Joseph Bazalgette, C.B., C.E., on the
Sewerage of Brighton. It is preceded
by the following retrospect of the re-
sults of some of the methods which
have from time to time been suggested
and tried for the better ventilation of
the sewers of towns :

The removal or treatment of the
gases resulting from decomposition in
sewers in an inoffensive manner is a sub-
ject which during the last half-century
has received much consideration. When
in 1850 I was conducting experiments on
the ventilation of the sewers of London,
I had the advantage of consulting with
that eminent chemist, Professor Faraday,
who had previously given much attention
to the subject, and who, in his evidence
before a Parliamentary Committee as
early as 183-4, had expressed the opinion
that it was beset with great difficulties.
Subsequently I visited some of the mines
in the north of England and in Wales, in
order to see how far any of the modes
adopted for their ventilation could be
applied to the better ventilation of sew-
ers, and I became acquainted with most
of the suggestions which have been made
for otherwise dealing with the gases
generated in sewers.

In 1858 a Committee of the House of
Commons, consisting of Lord Palmers-
ton, Lord John Russell, Lord John
Manners, Sir Benjamin Hall, Mr. Robert
Stephenson, and Mr. Tite, directed me
to make experiments on the effect pro-
duced by extracting and burning the
gases of sewers by means of furnaces.
Those experiments were conducted with j
the furnace in the clock-tower of the j
Houses of Parliament, and I subse-
quently gave evidence before that Com-
mittee, to the effect that in the immedi-
ate neighborhood of the furnace the in-
draught was found to be very strong, but
that, whilst the supply of air was drawn
with great force from the sewer inlets
close to the furnace, the air current pro-
duced in the sewers at a short distance
from the furnace was scarcely perceptible.

The Committee of the House; of Com-
mons reported that, although such a
process might be advantageous to sew i
within a short distance of the furnace, it
could not be successfully applied to any
wide range of sewers, on account of the
number of openings which unavoidably
communicate with them, the nearest of
which to the furnace would supply it
with atmospheric air, whilst the gases in
the further part of the sewers and house-
drains would remain unaffected by its
action.

In a mine there is but one downcast
and one upcast shaft, and all the air
brought into the mine at the downcast
shaft can be directed and conducted at
will, and discharged at the upcast shaft
after it has passed through the whole
length of the various galleries ; whereas,
in an ordinary system of town sewers,
provided with inlets for the admission of
water at every house-drain, gully, and
branch sewer connection, the beneficial
effect of furnaces, fans, or air pumps, be-
comes limited to a comparatively small
area ; but wherever furnaces exist in the
neighborhood of sewers, it is neverthe-
less desirable to connect them with the
sewers. In long lines of intercepting and
outfall sewers, which have no branch
connections or openings along their
route, furnaces have been and may be
used with the same beneficial results as
in mines.

In 1866 Dr. Miller, F.R.S., and I con-
ducted a series of careful experiments on
the effect of ventilating sewers through
charcoal, which extended over a period
of twelve months and embraced a large
draining area. The sewers were cut off
from all other means of ventilation, ex-
cept through charcoal trays of various
forms fixed in the ventilators. We found
that whilst dry charcoal is an efficient
means of deoderizing and disinfecting
sewage gases, its introduction into the
ventilators produced a sensible retard-
ation of the current of air in the sewers,
and the carbonic acid in them was in-
creased on an average of our experiments

410

VAN NOSTEAND'S ENGINEERING MAGAZINE.

from .106 to .132 per cent., and the mean
temperature in the sewers was thereby
raised from 50.8° to 56.2°. The bene-
ficial effect of charcoal is, moreover, con-
siderably reduced by moisture, and it
therefore requires renewal at no very
distant periods, varying according to the
state of the atmosphere. Charcoal may
be introduced with advantage into such
ventilators as are the cause of any special
annoyance ; but, as they retard the cur-
rent of air, their number and area would,
if generally adopted, have to be increased
to an extent which is for many reasons
undesirable.

Shafts connected with the sewers and
carried through lamp-posts in the streets,
or to the tops of adjoining buildings,
away from the chimneys and upper win-
dows, might in many cases be so con-
structed as to ventilate the sewers effi-
ciently, provided they were sufficient in
number and in the area of their openings.
But there is frequently much difficulty in
obtaining the necessary consent for ven-
tilators up the sides of houses on account
of their having to be placed on private
property.

The use of sulphurous acid and chlo-
rine gas placed in ventilating shafts, and
various other chemical or mechanical
antidotes, have been attended with more
or less beneficial results, and most of
them may, under favorable circumstances,
be applied in particular places with ad-
vantage ; but all these modes of treat-
ment require such constant attention and
frequent renewal that they thus become
liable to failure.

In order to prevent the evolution of
noxious gases from sewage, the great ob-
ject to be attained is its dilution and
rapid removal, before decomposition has
set in, by a copious supply of water,
through sewers having sufficient falls to
prevent the accumulation of deposits in
them. Where these conditions cannot
otherwise be sufficiently secured, the
sewers should be kept clean by periodical
flushing. Road detritus, if allowed to
enter and deposit, in the sewers, will ac-
cumulate and precipitate with it much of
the sewage which otherwise would not
deposit. The efficient scavenging of the
surface of the roads and the interception
of the detritus washed off them during
heavy rains by properly-formed catch-

pits, are therefore essential to the main-
tenance of clean sewers. Macadamized
chalk, or gravel roads, especially those
having steep inclinations, require par-
ticular attention in these respects. In
1878 there were in the metropolis 1,700
miles of roads, of which about 1,000 were
macadam or gravel, and from the surface
of the whole were removed in one year
over 600,000 cubic yards of detritus, at a
cost of about Is. per yard ; whilst about
100,000 yards were removed from catch-
pits under the gullies,, at a cost of 2s. 6d.
per yard, and 20,000 cubic yards were
taken from the sewers at a cost of about
25s. per yard. Thus it will be seen that
effective scavenging and the construction
of proper catchpits are economical as
well as being advantageous to the con-
dition of the sewers.

There are few who will not now rec-
ognize that the removal of the refuse of
large towns by water is so vastly superior
to any other known method as to have
caused it to be an essential in these days
of civilization and refinement. But the
underground carriers must be freely
ventilated or the gases generated in them
will escape into the houses, where, being
shut up and but slightly diluted with at-
mospheric air, they are inhaled day and
night, and become injurious to health,
and dangerous. It will be found upon
close investigation that in the great ma-
jority of cases where persons have suf-
fered from the effect of sewer gases, the
mischief has arisen from defective house
drainage and not from the public sew-
ers. Every house drain should be formed
of stoneware pipes, laid with sufficient
fall to prevent the accumulation of de-
posit, and ventilated from its upper end
to the roof of the house, but very few
are so ventilated.

The gases escaping from efficient sew-
ers ventilated on to the surface of the
roads may nevertheless, in certain states
of the atmosphere, be offensive in the
immediate neighborhood of such ventil-
ators, and although no universal system
of ventilation has yet been discovered
which can be always applied without any
inconvenience, some satisfactory mode
may in every case be selected, according
to the varied conditions of the localities
to which it has to be applied. Attention
to the foregoing principles of construe-

VENTILATION' OF SEWERS.

411

tion and maintenance of the sewers will
very materially promote their ventilation
without offense or injury.

At a meeting of the Yorkshire Associ-
ations i){ .Medical Officers of Health,
held in Doncaster in June —

Mr. B. S. Brundell, C. E., read a paper
on "Ventilation of Sewers." He said
the question of the ventilation of sewers
was by no means easy to treat in an in-
teresting manner, and still more difficult
was it to make the subject instructive, as
much had been already written and

id on the subject. He would, however,
endeavor to give a practical turn to the
subject. It might be taken as clearly
established that if the sewers of our
towns were constructed with adequate
self-cleansing "falls," and with proper
flushing arrangements, and if at the out-
fall a free discharge of sewage could be
secured at all times, there would not be
much need for ventilation ; for there
would be no foul matter in the sewers out
of wThich to create what is commonly
called sewer gas. But, unfortunately, the
great majority of towns were so situated
that the sewers could only have gradients
with small "falls," and too frequently the
outfall was obliged to be either partly
submerged, or, as in the case of pump-
ing works, at certain periods inoperative,
and hence sewage was stagnant for hours
near the outfall, or moving so sluggishly
that decomposition was set up, and sewer
gas resulted. The question, therefore,
arose how this could best be got rid of.
The mode of ventilation of sewers which
met with most favor was that of open
gratings on the surface of the streets, and
those had been found effective. In Leeds,
and in some other towns, the gully grat- 1
ings were now made to act as ventilators,
the traps formerly used being removed.
He had grave doubts as to the wisdom of
leaving a place of escape close to a house
or a shop door. Some openings emitted
much more sewer gas than others ; and
it was therefore not only necessary to
provide ventilation, but to ensure a cur-
rent of fresh air. The openings conse- ;
quently should not only be numerous,
but well placed for the purpose — in fact, l
a constant interchange between the outer
air and the sewers should be aimed at.
"Where there was a tendency for the gas
to travel up the sewers, flap-valves should

be placed so as to stop the upward (air-
rent. No doubt much could be done by
the owner of a house in the construction

of BUCh connections as would obviate the
risk of sewer-gas finding its way into the
house; but if the main sewers were prop-
erly ventilated the householders' precau-
tions would not be nearly so necessary as
they were at present. Another mode of
ventilation which had been much advo-
cated was that of exhaustion by connect-
ing the sewers of a town with the fur-
naces of steam boilers ; but this necessi-
tated a peculiar construction of sewer
which would allow of the air being drawn
from the sewers by the furnaces ; and it
was not clear what length of sewer could
be so exhausted. Moreover, the furnaces
of boilers were not always at hand. Still,
no doubt, the principle was a good one,
and he had tested it with success. The
experience of Brighton was not very en-
couraging in this direction ; and anything
like the application of this principle of
ventilation to the sewers of a town could
not, he thought, be entertained. Venti-
lation by means of pipes carried up the
chimneys of houses was sometimes adopt-
ed, terminating with an exhaust ventilator,
and which had been successful in some
cases ; but it should be carried out with
great care, for in some places this sy t^ai
had been traced as the cause of blood
poisoning. He would urge, as one con-
clusion to which he came, that main
sewers should be systematically flushed;
and the outfall of main seweis, as a rule,
should have falling-doors, so as to prevent
wind blowing up the sewers.

Mr. Masters read a paper on " The Cir-
culation of Air in Sewers." Sewer-con-
struction, he said, had been broadly dis-
tinguished by the terms " sewers of de- .
posits" and "sewers of suspension."
The former involved a system of flushing ;
in sewers of suspension a continual flow
and circulation of air were provided.
They were told on the best authority that
sewers to be self-cleansing must have a
certain grade, and he quoted from a table
of inclinations, wrhich gave the grade of
a self-cleansing 15 inch drain at a fall of
1 in 250. He believed the most effectual
means of creating a good current of air
and ensuring ventilation and thorough
cleansing of the sewers was by a constant
stream through the whole length of the
sewers (instead of an occasional one), at

412

VAN NOSTRAND'S ENGINEERING MAGAZINE.

a velocity of not less than 3 feet per sec-
ond. It had been proved that the air
would follow a stream traveling at 2 feet
per second, in preference to rising to the
highest point of the sewer. Any system of
sewerage which provided for the removal
of the sewage at so slow a rate that sewer
gas was left behind must be imperfect.

Dr. J. M. Wilson read a paper on " The
Ventilation of House Drains." He said
the house system of drainage should be
provided with means of cutting off the
waves of sewer air, or at least of giving
them an exit in a way harmless to the
house inmates. He wished chiefly to
elicit an opinion as to how far some prin-
ciples of drain ventilation were satisfac-
torily answered by the requirements of
the Local Government Board in their re-
cent by-laws applicable to house drainage.
That air from the house drains or sewers
was in it's effects injurious to health, and
capable of originating definite forms of
disease, they, as medical officers, had too
many opportunities of confirming. These
connections were as a rule very defective,
He proceeded to discuss the by-law to
which he referred. If, he said, it could
be satisfactorily agreed tljat the plans
proposed answered the theoretical re-
quirements of the laws governing the ac-
tion uf gases, and — as their adoption was
already being proved to be— more effectual
than any previous practice in shutting off
all air from the drains from entering the
house, then he thought they might safely
leave it to their engineering friends
to smooth away any practical difficulties.
To sanitary authorities and the public
they could safely recommend a system
which satisfied the principle of drain ven-
tilation, and the adoption of which they
might reasonably anticipate would rid us
yet more of the class of diseases caused
by what had been called aerial sewage.

The Chairman remarked that the ques-
tion of the correctness of the germ theory
underlay the discussion, and an impor-
tant point to be considered was whether
sewer-air was capable of carrying germs
of disease.

Dr. Whitelegge, in referring to the first
paper, remarked that if the ventilators to
sewers were constructed sufficiently close
to each other, it would be impossible for
poisonous gas to accumulate in sufficient
quantity to prove injurious.

Dr. Himes said that in the whole course

of his experience he had never met with a
case in which sewer-gas had produced spe-
cific disease. If it were true that sewer-gas
did cause specific disease, medical officers
would find themselves in the difficulty of
having to condemn the present system of
drainage in large towns. But where was
the proof that sewer-gas was the cause of
disease? A case of typhoid fever was
found in a house, and an examination
showed that the house was in direct com-
munication with the main sewer. But so
were thousands of houses in which there
was no fever. In Sheffield there were
acres upon acres without sewers of any
kind, and so there were hundreds of vil-
lages, yet they did not find these districts
any better off in respect of zymotic dis-
eases. In his opinion it was matter for
regret that sanitary authorities gave al-
most their entire attention to the causes of
zymotic diseases, instead of endeavoring
also to prevent, as they could in a great
measure, that frightful scourge consump-
tion, and probably also the large number of
deaths from bronchitis and pneumonia,
which were largely attributable to the
same causes. But to return to the question
of sewer-gas, in looking through the death-
rate of his borough he did not find in
those seasons in which the decomposition
of sewer matter was most active that
so many deaths from zymotic diseases
were registered. In Croydon, where
typhoid fever had been more or less prev-
alent, the bad smells found in many of
the houses were assumnd to be sufficient
proof that sewer-gas was the cause of the
fever. He did not think that was sufficient
proof. His experience did not fortify the
second-hand opinions which had been laid
before the meeting relative to sewer-
gas.

Dr. Wills suggested that water-spouts
as conductors of sewer-gas were prefera-
ble, at least from an aesthetic point of
view, to open shafts over which one had
to walk.

Mr. Hodgson, C. E., remarked that it
was a fundamental error to suppose that
a certain amount of velocity in a sewer
was all that was necessary to carry off
sewer-gas. In connection with sewer
ventilation, of whatever description, there
must also be a system of cleansing.

Dr. Whitelegge urged these points for
the acceptance of the meeting — namely,
that" sewer-gas did not mean merely a

FAILURES IX RAILWAY EMRAN KM KXTS.

413

mixture of well-known chemical gases ;
that sewer-gae did not necessarily give off
a bad smell: that it was not necessarily
heavier or lighter than the surrounding

air ; and that it was deleterious.

The Chairman said he apprehended
that sewer gas was the sum total of all
the vapors proceeding from the contents
of sewers — nothing more nor less, in fact,
than the results of decomposition, and
varying at different seasons and in differ-
ent temperatures, and in proportion to
the. contents of the sewer. In his. judg-
ment, a large amount of the most danger-
ous and pernicious gas was almost odor-
less. As the effect of its action, people
were deprived of a great amount of the
air they breathed. According to the
teachings of the last fifteen or twenty
years, all organic compounds in a stale
condition were prone to excite other stale
conditions in any organisms with which
they came into contact, and the admission
of these unstable compounds into our
bodies was therefore, according to mod-
ern science, a fertile scource of danger,

and if they did not set up changes or ac-
tions in our bodies it was because we

were in a condition to resist them. What
was true of zymotic diseases was also true
of noxious diseases arising from these
causes. Then in these sewers we had
the undoubted carriers of these noxious
germs. By means of the connection be-
tween houses and sewers the infectious dis-
eases of one house were carried to other
families. And we had these diseases let
into our houses in every possible way — by
bathrooms, by water closets, and by other
ways — and the only way of escape was by
complete isolation from our neighbors. He
frequently advised his friends to open out
all dead ends of pipes and drains, so that
there shonld be free and perfect exposure
to the air. If we could have impervious
floors and walls with, practically, open
ditches for drains, we should best stave
off disease ; those who lived in villages
would know quite well that the open ditch
was far less offensive than a good many
of our more expensively constructed
sewers.

FAILURES IN RAILWAY EMBANKMENTS.

By JOHN WILLIAM DRINKWATER HARRISON, Assoc. M. Inst. C.E.
From Selected Papers of the Institution of Civil Engineers.

The unusual difficulties encountered
by engineers during the last five years in
the construction of railway earthworks,
have been to a great extent attributable
to the abnormal state of the weather dur-
ing that period. In no other class of
work can a completely successful result
be anticipated with so little confidence,
and a satisfactory solution of the diffi-
culty still appears remote. From the
great outlay which is often' necessary to
restore the ground after an extensive
slip, it may be questioned whether greater
precautions, and consequently increased
expenditure during construction, are not
desirable. Probably the material does
not exist which, if thoroughly freed from
the presence and action of water during
the process of construction, would fail to
form a permanently stable structure ; the
value of the forces of cohesion and fric-
tion depending so largely on this con-
dition.

The separation of the sound or dry
material from the unsound is a matter of
the first importance, and sufficient at-
tention is not generally given to it.
There are differences of opinion as to
what constitutes unsoundness, and a
practical definition of it is by no means
easy. The process of separation fre-
quently involves additional labor on men
who require great supervision ; land
whereon to deposit the soft earth is not
always available, and the common prac-
tice of casting it out on the sides of the
nearly finished bank is unsatisfactory.
Where burnt ballast is required, the
best method is to light fires adjacent to
the cutting, and to burn the wet ma-
terial. Considerable importance is be-
lieved to attach to this point, as the com-
mencement of slips of a serious nature
has been traced to the admission into an
embankment of two or three wagons of
" slurry."

414

VAN nostrand's engineering magazine.

On the recently constructed Notting-
ham and Melton railway several serious
slips occurred. Some idea of the char-
acter of the material may be formed
from the fact that one-fortieth of the ex-
cavations was burnt into ballast for use
on temporary roads only. Great care
should be taken to drain transversely the
water which collects in the ballast so
used, otherwise, the temporary road sink-
ing to a lower level than the bank on
either side, a trench retaining water is
left in the center of the embankment,
wTliich is a fruitful source of trouble.
The rule adopted on the above line in
forming the slopes of earthworks was :

For cuttings and embankments under 25 feet

deep, slope l£ to 1.
For cuttings and embankments above 25 feet

and under 40 feet deep, slope If to 1.
For cuttings and embankments above 40 feet,

slope 2 to 1. •

Any attempt, however, to arrive at a
definite angle of repose for such material
is not likely to be successful, several of
the slips having assumed a slope of about
8 to 1.

Experience fixes 30 feet as the limit of
height to which it is advisable to carry
a bank of blue clay ; the necessarily slow
progress made in higher banks exposes
the earth on the leading face so much to
atmospheric influences, that, in a bad
season, the slope is continually in a soft
condition, and is an unfit foundation for
the reception of any material. To avoid
this evil, by making more rapid longitu-
dinal progress, several of the heavier em-
bankments were formed in two lifts. If,
however, the season is a good one, it is
better to tip a bank to the full height in
the first instance. In tipping it at a
lower level there must be a sufficient al-
lowance for settlement, otherwise the base
on which the higher lift is to rest will be
too narrow. Since this settlement varies
in different soils from 2 to 6 inches in
the foot, the difficulty in determining
beforehand what allowance is necessary,
renders this contingency of a narrow
base a not unfrequent occurrence, and
obviously necessitates beveling the ex-
tra width on the slopes of the lower lift,
which is always to be avoided. Then
again, the surface of the lower bank
being in an uneven state induces the col-
lection of water and consequent satura-
tion of the work.

On sidelong ground, in pasture land,
the grass affords a sufficiently smooth
surface to induce a movement in
the bank. The author believes that a
system of surface digging to a depth of
9 inches is preferable to the formation of
benchings. The latter need careful
drainage, and when cut at right angles
to the center line of the railway, the
mound formed from the excavation of
the benching, being composed mainly of
light turfy soil, gives way under the
weight brought on it, and so not un-
frequently causes a failure extending into
the bank. The author recently had oc-
casion to widen an embankment for
siding purposes ; one part of the slope
of the already formed bank was benched,
the other surface was dug, and it was
found that the latter stood better than
the benched portion. In this case, how-
ever, though great care was taken to
drain the benchings when formed, a
settlement may have taken place in the
old bank, causing an accumulation of
water in the benchings.

Desirable as it undoubtedy is to ascer-
tain, by borings, the nature of the ma-
terial to be excavated before commencing
operations, little or nothing can be learnt
in this way as to the probability of the
subsequent occurrence of slips ; nor does
it follow that a material which will stand
well in cutting will form an equally good
bank, and vice versa. The excavation
from a cutting on the Nottingham and
Melton railway, which was deposited in
a spoil bank, stood well at a slope of 1
to 1 or less ; whereas the cutting whence
it came gave no little trouble, though
its slopes were flattened to 2 to 1. In
this case the presence of " backs " caused
the trouble in the cutting, the process of
excavation and removal obviating this
danger in the bank.

Slips are more frequent in autumn,
after a dry summer, than at other seasons.
The probable explanation of this is that
the cracks formed by the sun collect the
rain, and where these cracks occur near
weak points of the bank, the bank fails.
To prevent, as far as possible, the oc-
currence of cracks, great care was taken
to obtain a good growth of grass. It has
been suggested that a layer of burnt
ballast 6 inches thick, placed beneath the
soil in which the grass is sown, would
not only be useful for drainage, but also

FAILURES IN RAILWAY EMBANKMENTS.

415

protect the elay from the effects of the
sun.

The slope assumed by plastic clay,
when first tipped, seldom exceeds 1^ to
1. Now although the slope which is
ultimately to be given, and which is con-
sidered necessary for the stability of the
work, may extend to 2 to 1, for reasons
of supposed economy in working and to
give time for any extra settlement beyond
that allowed for, the embankment is usu-
ally left at the steeper slope for periods
extending in some instances to several
years. During this time, it appears to
the author that, allowing the more ex-
tended batter to be a correct estimate of
what is necessary, an excessive strain is
placed on the work. The slips which oc-
cur while the bank is in this condition
are sufficiently frequent to lend some |
force to this argument. Though these
slips may not be of a heavy character,
nor even extend beyond the ultimate
slope line, it is noticed that they remain
weak points in the work and occasionally
lead to serious disturbance. To remedy
this, it seems desirable that the process
of forming the slopes should be carried
on as nearly as possible simultaneously
with the construction of the body of the
bank. The objection to this system on
the score of expense is not a serious one ;
and alllowance for further settlement
might be made by slightly increasing the
width of the formation ; indeed, in ground
of this character, a somewhat extended
formation may be beneficial in other
ways. The additional outlay in land in
most districts is hardly worth consider-
ation, the main question in cost being the
increased quantity of excavation neces-
sary.

In treating slips after their occurrence
two methods were mainly adopted :

1st. The toe of the slip was burned
into a compact mass of ballast, the width
at the base varying from 8 feet to 20 feet
or more. This retaining wall, for such
it virtually was, having been formed, the
foot of the slip was weighted as far as
possible, and the slope was left concave
where practicable, having a versed sine
one-thirtieth of its length. The founda-
tion of the ballast heap was 2 feet below
the original surface. In no case did this
wall of ballast give way, though in sev-
eral instances the slip rolled completely

over it, and a fresh heap had to be

formed at a greater distance from the
line. As the circumstances were excep-
tional, any details as to cost would be
misleading; but it may be stated that 1
ton of coal was sufficient to burn about
10 cubic yards of ballast.

2d. Trenches were cut through the
slips at right angles to the direction in
which the ground was moving : the width
of these trenches varied from 2 to (.) feet,
and having been carried 18 inches or 2
feet into the solid ground below the line
of the slip, they were filled with stones,
the whole of the timbering necessary for
their excavation being, generally speak-
ing, left in. This is obviously a costly
process, and was only adopted in extreme
cases, where the slips were delaying the
opening of the line. In excavating the
trenches it was noticed that but little
water was tapped at a lower level than 3
or 4 feet below the surface. That they
must be regarded as counterforts to
strengthen the slips more than as means
of drainage was shown by the fact that
several weeks after their construction the
surface of the bank 3 feet away from the
trench was in a soft, boggy condition.
Regarding them, then, simply as counter-
forts intended to strengthen a moving
mass of weak material, it was thought
that to carry them completely through
that mass would defeat the purpose for
which they were formed, and allow the
slip, or succession of slips, to continue
their course between the walls. It was
found that carrying them about two-
thirds of the way through the slip effectu-
ally checked its progress, and it seems
probable that a less distance than this
would have sufficed.

In all cases, where the trenches ex-
tended to the back of the slip, there was
no great quantity of water. The cause
of the majority of the failures appeared
to be the inability of the material to sup-
port its own weight, consequent on the
quantity of water with which it was
charged ; that this water is held in sus-
pension for a great length of time appears
probable, and the fact that the heaps of
ballast over which the slip had rolled
were found, when opened out, to be in a
dry and dusty state, shows that the
plastic nature of the clay prevents gravi-
tation, and the process of evaporation in

416

VAN NOSTRANDS ENGINEERING MAGAZINE.

a deep bank must be slow. More than
once where the base of the slip was on
the same level as, and extended to the

bottom of, the ordinary open' side ditch,
a pipe-drain filled with rubble was sub-
stituted with advantage.

CO-EFFICIENT OF SAFETY IN NAVIGATION.

By PROF. W. A. ROGERS.
Abstract of a Paper before the Society of Arts, Boston.

Prof. Rogers first referred to and ex-
plained the use of the co-efficient of safe-
ty in the calculation of the size of tim-
bers used in building from the experi-
mentally-determined breaking load. He
then proceeded to discuss the errors to
which observations to determine the posi-
tion of a ship at sea are liable, with the
object of finding how wide are the limits
of these errors, so that it might become
possible to find a co-efficient, as in the
case of the timber, by which this error
might be multiplied to secure absolute
safety, as far as safety depends upon hu-
man means and exertions.

This important question of how large
an error is liable to enter into the de-
termination in a ship's position appears
to have been almost wholly neglected, at
least in so far as published discussions
are concerned. It is not referred to in
the extensive press utterances nor in the
Court of Inquiry which followed the dis-
aster to the steamer Atlantic. In the
whole forty-three volumes of the English
Nautical Magazine, in the British Ad-
miralty Law, especially in the new code
adopted in 1849, in the Wreck Register,
published annually by the British Board
of Trade, nothing appears upon this
subject. If navigators proceed upon the
supposition that they can with certainty
obtain their position within one mile, to
say nothing of 300 feet (as reported to
have been stated by Capt. Williams of
the Atlantic), the wonder is not that so
many wrecks occur but that more do not
occur. Yet the general testimony of sea
captains in answer to inquiry is that one
mile is the ordinary limit within which
the co-ordinates of a ship's place can be
determined.

By tables of statistics of the shipping
of Great Britain since 1838, Prof. Rogers
then showed that there has been a large
increase of disasters in proportion to the
whole number of vessels, a fact which

justifies a new discussion of the whole
problem of wrecks and their causes. In
the following investigation it is proposed
to examine only those causes of wrecks
which in a measure seemed to have
escaped attention in official investigations.
These are:

1. Wrecks produced by causes clearly
beyond human control.

2. Wrecks resulting directly or indi-
rectly from over -insurance.

3. Wrecks caused by the deviation of
the compass.

4. Wrecks caused by errors of obser-
vation at sea.

The first inquiry is the most import-
ant one, as, if we can find the number of
wrecks from causes beyond human con-
trol, we may thus ascertain how many
are within human control.

By an examination of the records of
the Court of Inquiry for twenty years it
appears to Prof. Rogers probable that at
least seven out of ten wrecks occur from
preventable causes.

Under the second heading the follow-
ing facts may be given :

1. It is certain that more insured than
uninsured vessels are lost.

2. In 1868 there were in the Baltic 220
Swedish steamers, and, in 1867, 215 Brit-
ish. Of these 3 Swedish and 17 British
were lost. From 1857 to 1867 the ratio
is 10 British to 3 Swedish. The British
vessels were insured, the Swedish were
not.

3. Admiral Halstead, Secretary of
Lloyds, in a speech before the United
Service Institution, said : " The remedy
for shipwrecks, — what is it? I do not
pretend for one instant to be able to pro-
vide a remedy, and I do not know any-
body who can undertake to say what is a
remedy for shipwrecks, but I will tell you
this. If I could go on the Stock Ex-
change to-morrow morning, and, by hold-
ing up my hand, put a stop to all ship-

OO-EFFICTENCX OF SAFETY IN NAVIGATION.

417

wrecks upon the const, it would be a ques-
tion how I could eret Bafe with Life off the
Exchange. When I put that question to
him (Lloyds), he said: kItis perfectly
true, yon would stop our bread." We
have here the highest authority for say-
ing that the whole cjuestion of insurance
involves more or less of fraud, and that
ships are purposely wrecked. In 1866
Thos. Berwick was convicted for being
accessory to the destruction of ships ;
owned by T. Berwick & Son. On his
trial he confessed to having destroyed no
less than nine vessels in the course of
twenty years. The case of the Dryad and
the Harlequin in 1837 shows that in those :
days at least the question of insurance j
had a very definite bearing on that of
wrecks.

On the third heading the speaker said
that his investigations were far from com-
plete or satisfactory on account of the
difficulty of obtaining reliable data. Prof.
Rogers then discussed the discovery of
the variation of the magnetic needle
from the true north, and the amount and
the secular changes in amount of this
variation. The amount of this variation
could be determined and corrected for,
but the problem of the deviation of the
compass on ship-board is complicated by
other effects. An iron ship, or one hav-
ing any considerable proportion of iron
in its construction or cargo, becomes a
great magnet by the action of the earth's
magnetism, and thus disturbs its own
compass needle. In iron ships this devi-
ation often amounts to 50°, thus render-
ing the compass useless, unless some
compensation or correction is applied.
This subject was first investigated by
Capt. Flinders in 1811. The polar expe-
dition of 1818 fully confirmed Flinders' ex-
periments. The next important work was
that of Barlow, which led to Airy's method
of correcting the deviation by swinging
the ship and correcting the deviation by
permanent magnets or soft iron placed
in suitable positions near the compass.
But the most important discovery was
by Dr. Scoresby, who found that the
ship was itself a great magnet. In his
voyage in the Royal Charter, to test his
theoretical conclusions as to the changes
in the magnetism of the ship in different
positions; localities and other conditions,
he found them verified. He also found
a sensible difference in the variation be-
Vol. XXVII.— No. 5—29.

fore and after steam is up in the boilers
of a steamer. The effect of the heel of
the ship has recently been investigated,

and also the change in magnetic condi-
tion of the ship after launching, some
three months being required for anything
like a permanent and regular condition
to be attained. But even with all these
studies and the corrections arising from
them, there may often exist unknown va-
riations of very considerable amount,
yet the London Compass Committee, as
late as 1869, declare that very few ships
are lost from this cause. What shall be
said of ships that are never swung, and
whose masters know nothing of the laws
of variation? The loss of the City of
Washington is the best refutation of this
statement.

The fourth topic was next considered.
Under the offer of a reward of £20,000
by the British Admiralty, Morin, Maske-
lyne and Huygens made attempts to pro-
duce methods for determining the longi-
tude at sea within thirty miles. The
method of the latter was to use watches,
determining the difference in longitude
by the difference in time. This method
was unsuccessful with Huygens, owing*
to the variation in the rate of the watches
used with temperature changes. But
Harrison finally produced a chronometer
which, by the excellent workmanship of
its construction, gave results within the
required limits, and this method has since
been generally adopted. Even in obser-
vatories fitted with the most delicate ap-
pliances the difference of longitude is
difficult of exact determination. For in-
stance, the difference in longitude be-
tween the Greenwich and Paris Observa-
tories in 1755 was supposed to be 9' 16";
in 1830 it was found to be 9' 21.5", a dif-

ference of 5.5", or 1^ miles.

The range

between Greenwich and Brussels is ten
miles. Several determinations by differ-
ent methods by Dr. Bowditch upon the
long, of the Old State House at Boston
differ by 2.6 miles, and the mean is in
error by ^ mile. Yet all these are hardly
comparable with any single observation
on land or sea. Tables of determinations
of the longitude of Washington show a
range of 1£ miles, and the mean is in er-
ror 1.4 s. These figures illustrate the
difficulty of the determination even under
the most favorable circumstances.

For the determination of longitudes at

418

VAN NOSTKAND'S ENGINEEKING MAGAZINE.

sea, two essentially different methods
are used.

1. By "Lunar Distances," occultations
and eclipses of Jupiter's satellites.

2. By chronometers, assuming their
rate at the beginning of the voyage to
remain constant.

The latter method has been for a long
time regarded as far more reliable than
the former. To compare the two afresh,
Prof. Rogers presented elaborate discus-
sions :

1st, of the results of a large number
of land observations at fixed stations,
and also of sea observations, with the
following general results :

For fixed observations, comparing with
the mean result at any station, we must
expect an error of 1.5 m., with a range of
5.2 miles.

For fixed observations, using the moon's
tabular places, an error of 3.1 m., with
range of 12.9 m.

For lunar distances, with sextant on
land, an error of 10.21 miles, with range
of 24.2 miles.

Fur lunar observations at sea these
quantities should be doubled.

2d, of a large number of # chronometer
observations, including series from the
Greenwich Observatory; from the chro-
nometers of the Cunard Steamship Com-
pany ; by Prof. Bond of Harvard College,
in 1849 and 1850, and many others. As
a result of this discussion, Prof. Rogers
states that taking the mean of the value
given by Mr. Hartnuss, =0.98 s., and that
found by himself, =- 0.48 s., we have for
the average daily error of rate of all
these chronometers 0.73 s. At the end
of twenty days, therefore, the navigator
must expect from his chronometer alone
an error of 3.6 miles. We must look out
for an error of 3.6 X 3. 2 -=11. 5 miles (when
3.2 is a factor of. safety deduced from the
discussion), and the amount of his error
may prove to be at least twice this quan-
tity of twenty- one miles, all on the sup-
position that he has an average chronom-
eter, as this is independent of the error
of observation which must still be added.

Prof. Rogers then turned to the final
question: how near is it possible to find
the place of a ship at sea by astronomi-
cal observation? Confining himself to
the usual method, viz., the measurement
of the altitude of the sun with a sextant,
at a given time before it comes to the

meridian, for longitude, and of its cul-
mination for latitude, he enumerated
some of the errors to which this method
was liable. These are :

a. Instrumental errors.

b. Error in noting time. This is never
taken closer than Is. Multiplying by the
co-efficient 3.2, previously found, gives
an error amounting to nearly one mile.

c. From imperfect sea-horizon. This
may amount to several miles.

d. From the use of approximate data.
In ordinary practice the use of approxi-
mate corrections, and the lumping to-
gether of several of these, may easily
cause an error of five miles or more.

e. From latitude of ship and time of
observation. These may be very large,
and for the most part escape the attention
of the navigator.

f. From the error in the estimated run
of the ship between the morning and
noon observations. It is impossible to
give any definite estimate of the magni-
tude of this error, but it is likely to exceed
all the others combined.

In addition to these, Prof. Rogers gave
an investigation of errors of sextant ob-
servations in general, from which he de-
duced as an estimate for sea observations
an average error for latitude of about
1', and for time of about 6 s.

The German Ironclad "Konig Wil-
helm." — In the early part of last month,
this vessel made a six-hours' trial trip on
the completion of her repairs. She was
built in 1868 by the Thames Iron Works
Company, from the designs of Mr. E. J.
Reed, at that time Chief Constructor to
the British Navy ; and she was when
launched the most powerful ironclad in
the world. Commenced to the order of
the Turkish Government, which could
not complete its payments, the hull was
purchased by Prussia, and finished to
her order. Although now surpassed in
strength and weight of armament, the
Konig Wilhelm is a very formidable ves-
sel. She is 356 ft. long, and 60 ft. 6 in.
beam, with a displacement of 9757 tons.
The engines are 8000 horse power indi-
cated, giving a speed of 14J- knots. In
addition to the repairs rendered necessary
by the collisionwith the Grosser Kurf iirst.
the engines have been improved at a cost
of £7634, and the armor has been in-
creased.— Engineering.

Gordon's formula and radius of gyration.

419

GORDON'S FORMULA AND RADIUS OF GYRATION.

By Rd. RANDOLPH, C.E.
Contributed to Van Nostrand's Engineering Magazine.

Although civil engineers and bridge
builders have generally adopted a certain
formula for the construction of columns
and other compression members of iron
structures, it is doubtful whether any of
them could give a satisfactory reason for
the employment of some of the quantities
which are used. When Gordon an-
nounced a formula based upon a long
series of careful experiments by Hodg-
kisson with columns having a solid rect-
angular cross-section, it was adopted
with full confidence, from the fact of its
having so practical a foundation. But
when it was attempted to apply the same
to columns having an irregular cross-
section, it was seen that in such cases it
was no longer applicable ; and it became
necessary to substitute for the least di-
ameter some other factor. From what
considerations this factor was determined,
it seems that all the authorities are si-
lent. Professor Rankine, whose work
on engineering is held in such high re-
pute, uses language on this subject, so
different from the exact statements of
science, that it would indicate a want of
confidence on his part in what he pro-
pounds. After giving certain modifica-
tions of Gordon's formula, he says — "but
from the nature of the calculation these
results must be regarded as rough ap-
proximations only." And in laying
down the one which has been so gener-
ally adopted by practical engineers, he
says — " but in many cases it may be
more satisfactory to take into account
the least radius of gyration of the cross-
section."

To one who cannot have a satisfactory
feeling about any formula of which the
data are not determined either in prac-
tice or theory, it becomes necessary to
analyze it and to inquire how the physi-
cal laws have been applied.

The first question which suggests it-
self in an inquiry into the Gordon
formula is — why does a column bend,
supposing it to be perfectly straight and
the force to be applied uniformly in lines
parallel with it axis? To this question

there can be but one answer; the differ-
ence in the elastic force of different
parts of the material. If this were abso-
lutely homogeneous, the only effect of
the pressure would be to increase the di-
ameter and to diminish the length ; as
there would be a simultaneous and equal
yielding at every point within the limit
of elasticity. If, however, owing to the
irregular resisting power of the ma-
terial, one side becomes shorter than the
other, the column will assume those
curves and deflections necessary to main-
tain the parallelism of its sides. As the
inequality of compression will not be
confined to one locality or to one side,
it may take any form between a regular
curve and a spiral. As soon as a deflec-
tion is determined by unequal compres-
sion, and the forces of action and reaction
form an angle with each other, a result-
ant force ensues at right angles with
the straight line between the two ends
of the column, and which reaches a
maximum at the point of greatest devia-
tion from this line. In the great ma-
jority of cases this greatest deviation
will be at the middle of the column ;
and being the least favorable for its
strength, this condition should be the
one contemplated in the formula which
provides for lateral yielding. As the
amount of deviation from the straight
line depends upon the difference in the
length of the two sides measured in
straight lines from the point of devi-
ation to the ends, the curves in the col-
umn on either side of this point do not
enter into the question: for they give
rise to minor lateral strains only, and the
provision for the maximum strain at the
middle point applies to the whole length
of the column. The case will, therefore,
be considered as a simple deflection at
the middle ; the difference of length of
the two sides being the departure of
two diameters from each other at the
point of deflection.

It is the object of the formula to em-
brace a coefficient, determined by experi-
ment, which shall represent the differ-

420

VAN NOSTRAND'S ENGINEERING MAGAZINE.

ence in the ratios of shortening of the
two sides by the compressive force of
the weight to which the column should
be subjected when bending is not con-
sidered ; and to determine from this the
deviation, the resulting lateral strain and
the necessary addition to the quantity of
material in order to resist this lateral
strain. If the Gordon formula, applied
to solid rectangular sections is correct,
the coefficient there used must express
this difference in ratio of compression, as
will be seen by deducing the formula
from the premises just referred to.

Let C denote the difference in ratio of
compression and L the length of the
column. Then C.L will be the difference

in the length of the two sides. Let D
denote the least diameter. One -half of
C.L is the side cb of triangle acb; and
as this is similar to triangle ade,

cbxde 7
-, — = cm.
ab

™ l". O.L L

That is, — x-^

C.L2

which is the deviation.

As the angle of deflection in such cases
are so small that the base and hypoth-
enuse of these triangles are practially
equal, they are so considered in this dis-
cussion.

If a force were applied at c at right
angles to de, one-half of the resulting
force would be resisted at each end of
the column ; and each would be in the
same proportion to half the original
force, as line ae to ad. Therefore half
the lateral strain is in the same propor-
tion to the force at either end of the

column as the deviation is to half the
length. That is,

C.L2
4D W.C.L

which is one -half the lateral strain ; W
denoting the weight per square inch on
the end of the column. The condition
of this strain is the same as if the column
rested in a horizontal position on a

fulcrum at the middle and had — ^~-

suspended from each end, except that it
must be considered to be at the same
time under longitudinal compression.
So that the effect of the weights would be
to compress still more the material be-
low the neutral axis at the middle and
above it at the ends where they receive
the first compression, both, however, re-
quiring the same expenditure of force.
The strains to be resisted on either side
of the neutral axis are parallel with the
column, tending to separate or compress
the particles in that direction with a ra-
pidity in proportion to their distance
from the axis ; which gives them a ca-
pacity of resistance in the same propor-
tion ; just as a resistance applied to a
lever is efficient in proportion to its dis-
tance from the fulcium.

The resistance to separation or com-
pression of the particles on either side
of the neutral axis resemble resistances
applied to different points along the short
arm of a bell-crank, representing the
semi-diameter of the column, to a weight
suspended from the long arm, represent-
ing the half length of the column. In
the case of a solid rectangular section, the
particles are disposed with uniformity
along the semi-diameter ; therefore their
combined resistance is the same *as if
they Were all located on a line half-way
on the semi-diameter, or a quarter of the
diameter from the neutral axis. And as
this is supposed to be in the middle of
the cross-section the condition is the
same on the both sides. So that the
force to be resisted by all the particles
will have the same proportion to the force
at the end of the long arm, as half the
length of the column has to one-fourth
of its diameter. That is,

Gordon's formula and radius of gyration.

421

W.C.L jL

2D J_2_
TT~"
4

W.C.I/
D2

is the amount of force per square inch of
section caused by deflection. Therefore
each square inch of the section must be
reinforced with sufficient material to re-

sist ' ' . And as W is the assumed

P T.2

strength of the material, R2 is the ad-

ditioual quantity, and 1+ * is the in-
creased quantity to be substituted for
each square inch of the original section.
So that instead of the capacity being W
per square inch, it is to be diminished,
when bending is also to be resisted, to

C.L2 ;

which is the Gordon formula when C is
substituted for the coefficient there given.
If the two ends of the column are
square, and the surfaces between which
they are pressed extend over the ends,
and are formed of material equally resist-
ant, any bending of the column would
require not only a compression on one
side of the neutral axis at the middle
but also on one side at each end. At
the middle, on the side towards which
the column bends, the bending is a re-
lief from the original compression and
meets no resistance ; but on the other
side the particles on each side of the
semi-diameter move towards it at the
same rate that they move towards the
pressing surface at each end, the two
end pressures being equal to the one at
the middle. Therefore the resistance in
the case of square ends is to that of
hinged or pin-bearing ends is as 4 to 2 ;
and when only one end is square, 3 to 2.
Rankine reports the coefficient of Gor-
don's formula in the case of square ends
to be 3 010 0 . If this is substituted for
C in the above, we have

For pin-bearing ends the additional •ma-
terial must be doubled, because there is
only half the resistance to deflection ;
which would make it

1500DS

1 +

3000D51

According to Rankine, however, Gordon
requires the additional area in the case
of hinged ends to be four times that for
square ends. This proportion is con-
trary to any theoretical reasoning on the
subject and leaves in doubt which one of
the cases was determined by the experi-
ments. In proposing a formula in which
the radius of gyration is substituted for
the least diameter, Rankine observes
this same proportion in the additional
area in the two cases ; but without ex-
planation substitutes the coefficient -3 oW
by 360TO"' 36,000 being the same as
Gordon's value for W.

But however satisfactory may be the
Gordon formula for solid rectangular
cross-sections, the analysis just made
shows that it cannot be correctly ap-
plied to irregular sections where the ma-
terial is not uniformly disposed along
the line of the diameter. The quantity

—would then have to be substituted by

another; which would be that multiplier
of the sum of all the particles on either
side of the neutral axis which would give
the same result as the sum of the prod-
ucts of the particles each multiplied by
its own distance from the axis. As be-
fore, it is a statical question like that of
the equilibrium of a lever under parallel
forces. If one arm . of a lever extends
ten feet beyond the fulcrum and one
pound is suspended from the center
of each foot, the effect is the same
as if ten pounds were suspended
from the center of the arm. This
would illustrate the solid rectangular
section. If, in addition to the weight
on each foot, ten pounds should be sus-
pended at the end of the arm the effect
would be the same as if twenty pounds
were suspended at the point three-quar-
ters of the distance from the fulcrum ;
which would illustrate a section having
a stem with a flange at the end of it.
Now these weights represent the part-
icles of material in the section whose re-

422

van nostrand's engineering magazine.

sisting power is in direct proportion to
distance of each unit from the axis.

With the view of the subject it is diffi-
cult to conceive how the radius of gyra-
tion, which finds its application only in
dynamical questions, could have been
introduced into the formula. To see the
distinction, consider the example of a
revolving wheel about a vertical axis
whose speed is maintained or uniformly
accelerated by the application of a con-
stant force, such as a descending weight.
On the principal of the lever each par-
ticle, by its inertia, offers a resistance to
the force in proportion to its distance
from the axis of rotation. If one of
these particles is moved to a greater
distance from the axis, its original ve-
locity cannot be maiDtained without a
greater expenditure of force than it re-
quired before ; because this would re-
quire the same pressure through a long
as through a short lever. But at the
same time the particle must increase its
velocity, if the general rate of rotation
is to be maintained ; which will require
another increase in the force applied.
If the distance from the axis is doubled
it will require the mass, and consequent
inertia, to be reduced to one half in order
that its original velocity or original rate
of acceleration may be maintained with
the same application of force. But as
its velocity or rate of acceleration must
be doubled in order to preserve the gen-
eral rate, the half mass must be divided
by two. That is, to say, that in order to
preserve the conditions of motion of a
revolving body or system, the mass of
each particle must remain in proportion
to the square root of its distance from
the axis ; while their combined influence
will be expressed by the sum of the
products of the particles each multiplied
by the square of its distance. That
distance from the axis which, being
squared and multiplied by the sum of
the particles, produces this result, is
called the radius of gyration. And
whatever changes are made in the mass
or position of the particles in reference
to the axis, the square of the radius of
gyration must remain constant in order
to preserve the condition of motion of
the system.

But the question of statical resistance
to tensile or compressive strains on either
side of the neutral axis, resulting from the

effort to bend a column, involves no other
consideration than the number of particles
or fibers and their average distance from
the axis. To this question the radius of
gyrations has no application whatever,
and its retention in the formula will
cause constant discord in all future at-
tempts to obtain a true co- efficient de-
rived from experiments.

It is evident that the quantity — in

the process which results in the Gordon
formula must be exchanged for one which,
being of the same value in solid rectan-
gular sections, will be equally correct in
all others. This might be called the
radius of resistance, for the resistance is
the same as if all the material were con-
centrated at the end of it. This quantity
can be nothing else than the distance
from the neutral axis to the center of
gravity of that part of the section on one
side of the axis : for a lever cannot apply
all its forces to any fulcrum except the
one of equilibrium,

Let the new quantity be denoted by R

and substitute it for-—. We will then

have

WC-L L

"2D X 2 W.C.L2

4D.R

O T 2
for the strain per square inch, and -p^r-

4D.R

for the increase of each square inch, and
W

1 +

C.L5

4D.R,

for the weight per square inch to which
the column is to be subjected so that it
may resist compression and bending both,
both end bearings being square.

Supposing Gordon's co-efficient, 3*oVo>
to be correct, the formula for square
bearing ends would then be

1 +

1200GD.R

For other modes of bearing the addition
to 1 in the divisor of W would be in the
proportions before mentioned.

The value of c can only be expected to
be sufficiently constant to ensure the er-

ON SEWER GAS AS A FACTOR IN THE SPREAD OF EPIDEMIC DISEASES. 423

rors being confined to narrow limits and however, for more experiments, for it
to enable it to serve the practical purpose should be determined with more certainty
for which it is employed. There is need, than has yet been done.

ON SEWER GAS AS A FACTOR IN THE SPREAD OF

EPIDEMIC DISEASES AND ON THE DIRECTION AND

FORCE OF AIR CURRENTS IN SEWERS.

" Deutsche Vierteljahrsschrift fur offentliche Gesundheitspflege," for Abstracts of the Institution

of Civil Engineers.

Part I. — By Dr. Soyka, of Munich.

The author draws attention to the fact,
that while England was the first country
to introduce an improved system of sani-
tation, it was in Munich that the theory |
of the dangerous nature of sewer-gases
originated ; a doctrine which is receiving
a considerable share of attention in Ger-
many, the tendency being greatly to ex-
aggerate the danger. According to this
theory, the air contained in the sewers,
on escaping into the streets and houses,
occasions the spread of epidemic diseases.
In England this doctrine is gradually
taking the place of the favorite, but some-
what exploded, notion of infection by
means of the wTater- supply. For, whereas
formerly whenever any impurity in the
water was detected this was at once made
answerable for any outbreak of typhus
or cholera: so now typhus, diphtheria,
and other diseases of this type, are im-
mediately declared to be caused by some
faulty drain or water-closet. It is fre-
quently not even considered necessary to
prove that there has been any actual
escape of sewer-gas, and no attempt is
made to trace the possibility of any con-
tact of the patient with such gases. The
convenience of making the foul gas re-
sponsible often, indeed, hinders any prop-
er investigation from being made into
the impure gases in sewers, latrines, and
other possible causes of infection. In
considering the subject, all cases of sud-
den death or illness caused by inhaling
similar places, may be left out of the
question, for what is now to be dealt
with is not sewer poisoning, but the
spread of certain diseases, either of an
endemic or epidemic character, which
arise in consequence oi the reception
into the system of an organism, which
there multiplies and becomes the germ

of new cases of infection. For, while it
is impossible to deny that long continued
exposure to impure gases may cause a
feeling of illness and discomfort, it is not
pretended that the foul gas in sewers can
give birth to the germs of typhus, diph-
theria, &c, but only that such gases serve
as the medium in which these organisms
are suspended and conveyed to the
patient. The author gives a table show-
ing the mortality from typhus, or so-
called " enteric fever," in a number of
English towns, before and after the com-
pletion of the sewering; and some special
tables relating to Croydon, showing a
spring and an autumn maximum in the
cases of zymotic diseases. Dr. Buchanan
is quoted, and blamed for contenting
himself w7ith the fact that the infected
houses, in the latter case, were connected
with the sewers, without making any at-
tempt to prove that the sewTer-gas escaped
into the dwellings. He stated, indeed,
j that no smell of sewer-gas was percep-
tible, and argues from this fact that the
inodorous gases were the most dangerous
ones. From an examination of the facts
respecting Croydon the author concludes
that there is no proof of the connection
i betwreen the sewerage system and the
! outbreak of typhoid fever which took
pl?.ce there in 1875. He observes that
j he has devoted a large share of attention
; to this particular case, because it is the
| only one in wThich an epidemic of this
nature has received careful scientific ex-
; animation, and because it greatly sup-
ported the theory of sewer-gas infection.
He states that this investigation forcibly
! recalls the report of Radcliffe, on the
1 cholera epidemic in 1866, and his theory
that the spread of the infection was caused
by the mains of the East London Water
Company, whereas Letheby most convinc-
I ingly proved that the supply-pipes of the

424

VAN NOSTRAJSTD'S ENGINEERING MAGAZINE.

Commercial Gas Company might with
equal reason be suspected (i.e., because
both companies served the infected dis-
trict), and that, as a curious coincidence,
the first case of cholera occurred at the
gasworks. Instances of outbreaks of an
epidemic character are always more or
less traceable to some one similar source
of infection, and for this reason the water-
supply, the milk, and such like, have been
at various times accused. In a similar
way Drs. Scott and Littlejohn attributed
the fever-outbreak in Selkirk in 1876 to
the bad drainage, and the Baden-Baden,
Gibraltar, Caius College, and Dublin epi-
demics have all been set down to defects
in the sewers. Dr. Soyka further refers
to other diseases, such as erysipelas,
bronchitis, and diarrhoea, which are said
to have been propagated by sewer-gas.

Passing on to foreign experience, and
selecting typhus as being essentially a
disease whose spread is due to excremen-
titious matter and the emanations there-
from, the author gives careful tables of
the health statistics of Hamburg, Dantzic,
Prankfort-on-the-Main, and Munich, both
before these towns were provided with a
regular drainage system and after the
drainage was completed ; and shows by
these figures that the death-rate from
typhus has greatly decreased since the
towns were thoroughly sewered. Taking
another of the zymotic diseases, diph-
theria, and considering the question
whether or not it is gradually taking the
place of typhus, he shows that the former
is essentially communicated by direct
contact, and that it is a disease infinitely
more destructive in country districts
than in towns, and one with which sewer-
gasts can therefore have but little to do.
lie also considers the prevalence of en-
teric diseases in the sewered and the un-
sewered portions of the same town, and
shows that in every case proper drainage
has largely diminished the mortality from
these diseases. He gives the results of
the investigations of Mayer respecting
the cholera outbreak in Munich in 1873,
and shows that the streets provided with
sewers were much freer from illness and
death than those which were undrained;
the number of cases of illness being 230
per 10,000 in the undrained streets, and
only 114 per 10,000 in those streets which
were properly sewered. His conclusions
are as follow:

1. It has been seen, in the first place,
that the facts and arguments adduced in
favor of the sewer-gas theory are by no
means free from suspicion, and that, on
the contrary, the demonstration is faulty
and incomplete.

2. It has been proved that the sanitary
conditions, more particularly as respects
a special class of infectious diseases, have
become substantially improved in towns
provided with sewers.

3. That in towns in the various dis-
tricts of which different methods or sys-
tems of excrement-removal prevail, the
drained areas show no unfavorable prom-
inence in regard to the presence of infec-
tious diseases, and that, if indeed any
connection is traceable between the sew-
ers and such diseases, the influence of
the drainage is a favorable one.

4. That the spread of certain infectious
disorders (diptheria), which is believed
to be dependent on the state of the town
as respects the sewering, appears to de-
pend upon entirely different conditions,
and to put the whole matter briefly :

(1.) " The positive proof of a connec-
tion between sewer gases and the spread
of epidemic diseases is wanting."

(2.) "The majority of the experiments
hitherto made lead us to conclude that
the spread of epidemic diseases is entire-
ly independent of sewer gases, and that
those towns, or parts of towns, provided
with sewers are more favorably circum-
stanced, as evinced by their sanitary con-
ditions, than the same towns before the
drainage was commenced, or the districts
which are still undrained."

Part II. — By Dr. Aladar v. Bozsahegyi,
of Pesth.

The author states that at a time when
vast drainage works are being undertaken,
and so many important towns are adopt-
ing, or are prepared to adopt, the water-
carriage system, it is advisable that the
objections to this plan of excrement-re-
moval, which .have been raised on the
score of the dangers arising from sewer
gas, should be carefully and fully inves-
tigated. The theory that zymotic dis-
eases are really due to the entry of sewer
gas into dwellings is based upon the ob-
servation that the high-lying portions of
towns, and those inhabited by the
wealthier classes, which are then assumed

ON SEWER GAS AS A FACTOR IN THE SPREAD OF EPIDEMIC DISEASES. 425

to be the higher-lying districts, are more
liable to enteric diseases than the lower
quarters of towns. The proofs brought
forward in favor of this beiug that in
certain affected houses the drainage was
out of order, and that bad smells pre-
vailed in the houses situated in the upper
parts of towns. The reason alleged for
this being, because, owing to its chemical
composition, sewer gas is specifically
lighter than atmospheric air, and natur-
ally rises to these points ; moreover,
certain specific observations have been
recorded in which a positive rn'es-
sure was found to prevail in sewers. The
inference from all these facts is, that
sewer gas has a decided tendency to
force -itself outwards from the sewers,
and consequently into houses.

From a consideration of the static and
dynamic laws governing the movement
of gases it may easily be argued that
there are numerous factors which must
be studied before any decision on this
matter can be arrived at. Taking first
the chemical nature of such gases, the
author shows that the balance of evidence,
excluding certain misleading experiments
conducted with gases evolved from cess-
pools and closed vessels containing fcecal
matters, leads to the belief that in lieu
of being lighter than the atmosphere,
sewer gases, owing to the presence of
rather more than the usual amount of
carbonic acid, are really heavier than air.

The differences in specific gravity of
the sewer gas, due to the moisture it
contains, are next dealt with, and the ef-
fects of the greater heat of the atmos-
phere in houses than in sewers, and in
the sewers themselves than in the soil
through which they pass, are noticed.
The author shows that the flow of water
in the sewer has in many cases an impor-
tant bearing upon the air currents they
contain. The state of the barometer also
is not without a marked influence on the
sewer gases, and the force of the wind
has much to do with the pressure of
the air in the sewers. He points out,
finally, that the currents in different
parts of the same system of sewers have
in many cases a conflicting action upon
one another.

The author states that he has dwelt at
considerable length on these facts in
order to prove that the gases in the
sewers are exposed to numerous varying

influences, thus rendering it very diffi-
cult to establish any general laws. He
then details his own observations, which
took place during the summer months,
over a portion of the main sewers of
Munich. He employed tobacco smoke
to indicate the general direction of the
air-currents, and sulphuretted hydrogen
gas, with strips of paper dipped in acetate
of lead and moistened with glycerine, to
show the distances traversed and the time
occupied by gases in passing through the
sewers.

These experiments demonstrated the
fact that the general direction of the air-
cnrrents in the main sewers was down-
wards, i.e. in the direction of the flow of
the sewage water, and more markedly so
in the deeper lying sewers, i.e., those
nearest the outfall. At the soil pipe
openings into the houses the direction of
the air-currents was very variable ; more
frequently, however, there was a draught
into, rather than away from, the house.
The ventilating power of the running
water in the sewer appeared to the author
so important that he carried out a series
of experiments with tin pipes of elliptical
section and fixed at various inclinations,
having water flowing through them, both
as a flat or as a deep pipe (O or O); and
he gives a table of the air -velocities in
these pipes under various conditions.
His conclusions are as follow :

1. The air in sewers is influenced by
a large number of factors, varying both
as respects time and place, direction and
force.

2. The results obtained during the
summer months and when no rain fell
were, that the sewer gases rarely passed
upwards in the sewers, but, on the con-
trary almost invariably downwards ; but
that the more frequent tendency at the
same time, of these gases was to stream
outwards into dwellings.

3. House and street connections should
be guarded against the entry of sewer
gases, and means should be taken to di-
lute such gases freely with air.

4. The downdraught along the sewer
in the direction of its fall is very favora-
ble to this dilution with atmospheric -air
and to the exclusion of the sewer gas
from the lungs of the population, and
every means should be taken to render
the draught as powerful and as constant
as possible.

426

VAN NOSTEAND'S ENGINEEKING MAGAZINE.

AS TO THE DURABILITY OF BUILDING STONES.

From "The Builder."

While fully aware of the general at-
tention that has in all times been direct-
ed to the durability of stone, we yet
question whether the subject has been
anywhere exhaustively treated, either in
our own country or on the Continent.
Although holding closely to the need of
experience, we yet should not forget that
both chemical analysis and other methods
of scientific investigation have made
great strides of late, and that it may be-
come essential to the architect to inquire
how far they may throw light on the
question of durability. We may practi-
cally know the difference in the durabil-
ity of Bramley Fall and of Portland
stone, but if we know not only the fact,
but its cause, we have made a step in ad-
vance. This consideration will have
more weight from some observations
to which we shall have to refer as to the
durability of granite.

For a contribution of much value to
this investigation we are indebted to the
Director-General of the Geological Sur-
veys of the United Kingdom, Dr. Archi-
bald Geikie, F.R.S. It is from the note-
books of geological rambles, and as re-
garded from the standpoint of the geol-
ogist, that the observations to which we
have to refer have been extracted. None
the less, it strikes us, do they' form a very
valuable beginning. Our own experience,
and we doubt not that of many a reader,
is enough at once to contribute some ex-
amples to those which have been elabor-
ately investigated by Dr. Geikie; and we
look forward with confidence to the prep-
aration, sooner or later, of a compre-
hensive scientific work on the durability
of building materials, in which chemical
and lithological science shall have their
due parts, side by side with the verdict
of experience.

Dr. Geikie's researches have, in the
first instance, been directed to the older
burial-grounds in Edinburgh ; the rea-
son, of course, being, that as tombstones
are usually date-bearing monuments, the
means of comparing the progress of de-
cay and the lapse of time are unusually
precise. To these humble slabs we take

leave to add, especially for the benefit of
architectural travelers on the Continent,
the category of scutcheons and armorial
bearings. Many ancient buildings, espec-
ially in Italy, are adorned with stone
armorial bearings. Of these, the herald
will be in many cases able to indicate the
date with considerable accuracy. And,
speaking now only from memory, we
should say that a study of lithological
degradation in Italy, based on dated
works of this kind, will give results so
widely different from those obtained by
Dr. Geikie in Edinburgh as to point to
the primary canon, — that the first divi-
sion of any study of the subject must be
topographical, or, rather, climatological.
Dr. Geikie points out that the effect of
weather in a town is likely to be in some
measure different from that which is
normal in nature. The disengagement
of sulphuric acid from the reek and smoke
-of chimneys is one of the causes of the
more rapid decay of stonework in urban,
as compared with rural, localities. On
the other hand, the range of tem-
perature is likely to be less active in a
town. And the incrustation of the sur-
face of the stone with dust, smoke and
other inorganic as well as organic matter,
in town buildings, has to be born in mind,
although there may be a question as to
the action of such incrustation on the in-
terior substance of the stone.

Around Edinburgh the materials used
are of three kinds, — 1st, calcareous, in-
cluding marbles and limestones ; 2d,
sandstones and flagstones ; 3d, granites.
With few exceptions, the calcareous
limestones in the Edinburgh churchyards
are constructed of ordinary white sac-
charoid Italian marble. There may also
be observed a pink Italian shell marble,
and a finely fossiliferous limestone, con-
taining foraminifera and fragments of
shells.

The marble occasionally is employed as
a monolith, in the shape of an urn, vase,
or the like ; but it has been usually fixed
in a framework of sandstone. And it is
as to its behavior in the latter case that
the observations we have to mention will

AS TO THE DURABILITY OF BUILDING STONES.

427

prove to be novel to most of our readers.
Dr. Geikie has, in the first instance, sub-
jected specimens of the marble, both
when freshly cut and when long- exposed
to the weather, to microscopic examina-
tion. His view of the process of degra-
dation is that it is of a threefold charac-
ter. The process of weathering, he says,
in the case of this white marble, presents |
three phases, sometimes to be observed
on the same slab, viz. : superficial solu-
tion, internal disintegration, and curva-
ture with fracture.

With superficial solution we are toler-
ably familiar. It becomes apparent in
the gradual dimness that comes over the
polished surface of the marble. This is
effected by erosion, partly by the carbonic
acid, and partly by the sulphuric acid
contained in the atmosphere, and notably
in the rain that falls in towns. The
rapidity of the process in Edinburgh de-
pends very much upon aspect and expo-
sure to rain. Exposure for not more
than a year or two to the prevalent
westerly rains is enough to remove the
external polish, and to give the surface
a rough character. The granules of pure
calcite, which have been cut across or
bruised in the cutting and polishing pro-
cess, are first loosened or dissolved, and
then drop out of the stone. An obelisk
erected in 1864, in Grey Friars church-
yard, is cited as an example in which
the surface has already become so rough
and granular that it might be taken for
sandstone. The grains are so loosened
that a slight movement of the finger
will rub them off. The" internal struc-
ture of the marble begins to reveal it-
self. The harder knots and nuclei of
calcite project above the surrounding
surface, and irregular channels, from
which the lime has been carried away
in solution by the rain, resemble the
bleached and furrowed aspect of the
rocks on the side of a mountain.

Solution, or decay of some kind, seems
rather to be hidden than prevented by
the formation of a surface-crust. This
Dr. Geikie considers to form most rap-
idly where solution is most feeble in
its apparent action. Beneath it the stone
turns to a loose crumbling sand. In
time the crust cracks into a polygonal
network, and rises in blisters, exposing
the under material to rapid disintegra-
tion. A marble urn erected in the same

churchyard in the year 1792 is thus
crumbling into sand, although it faces
the east. The process, which Dr. Geikie
describes with elaborate minutiu ss. must
closely resemble that which may be ob-
served to take place with oolite stone
in London ; as, for example, on the
south face of St. Paul's, where thick calces
of a black color may at times be seen
to shell off, leaving partially disintegrat-
ed stone exposed to view.

It is the third form of decay, which Dr.
Geikie describes as curvature and frac-
ture, as to which, we think, the observa-
tions now recorded are the most novel.
This most remarkable phase is to be ob-
served in slabs of marble which have been
firmly inserted into a solid framework of
sandstone, and placed either in an erect
or a horizontal position. It appears as a
swelling up of the center of the slab,
which forms, as it were, a blister that
finally ruptureS. A case is cited of a slab,
30 in. by 22 in., and f in. thick, built
into the south wall of Grey Friars church-
yard. The date of the last inscription
on it is 1838, at which time it is pre-
sumed that the slab was smooth and up-
right. It has now escaped from its
fastenings on either side, though still
held firmly at top and bottom, and pro-
jects from the work like a well-filled
sail, to the distance of 2^- in. A series of
rents, one of which is one-tenth of an
inch in width, has appeared along the
crest of the fold. In another case, that
of a tomb erected in 1799, facing south,
and protected by overhanging masonry
from the weather, the inscription has be-
come partly illegible, the stone has
bulged out in the center, and cracks be-
gin to riddle the blister. On another
slab, twenty years older, dated in 1779,
on the west wall, the process of destruc-
tion has advanced to a further stage, and
since it was sketched by the author of
these notes, has altogether fallen out
and disappeared.

It is the opinion of Dr. Geikie that this
mode of destruction is due to the action
of frost. As to this we are disposed fully
to agree with him, and that from obser-
vations of our own which bear on the
subject. One set of these regard the
durability of marble where frost is un-
known, or rare. For example, we can
cite a large marble tablet built into the
wall by the eastern gate of the little

428

VAN NOSTRAND'S ENGINEERING MAGAZINE.

archiepiscopal city of Sorrento, which
contains (or did some years ago) a long
and perfectly legible Latin inscription, of
the date of the Spanish rule in Naples.
Again, on the gates of the City of Naples,
aud on the Castel Nuovo in that city) are
scutcheons of arms which have been de-
faced on some occasion of change of dy-
nasty, and on which the marks of the
chisel are so fresh that it is clear that the
absence of armorial bearings is not due
to the lapse of time, but to political
causes, and purposed violence. In those
instances, to which a very moderate ac-
quaintance with Southern Europe can no
doubt add <nany more, we have ample
proof of the monmental durability of
marble, although freely exposed, in a
climate where frost is very rare, and
never of sufficient intensity to get good
hold of the surface of the ground. The
other observations refer jjp the curious
permeability of limestone to wet. It
may, be said, perhaps, that the water
which collects on the interior surface of
a limestone or marble wall does not per-
colate, but is condensed by the cold of
the wall from the atmosphere. Weeping
through solid stone seems, indeed, in-
credible. But we can cite one instance
of a wall made of mountain limestone,
thoroughly well built, and 3 ft. thick,
in H.M. Dockyard, Pembroke. It is
the wall of a smithy. When it was
newly built, when the rain drifted on it
from the west the wet ran down within
the building as if the walls had been
of chalk, or some porous substance. We
do not assert that the wet did come
through the walls. But it appeared so
to do. And, at all events, this and
other experiences point to a hygromet-
ric condition in the purest and densest
limestones which is likely to have a very
destructive effect in the event of the
occurrence of frost directly after rain.

Dr. Geikie comes to the conclusion that
the lowering of the surface of marble by
superficial solution may amount to J- in.
in a century; a reduction to a pulveru-
lent condition in about forty years ; and
a total disruption by curvature and frac-
ture in a century. We only add the con-
dition that this must be where frost is
energetic in its action.

The endurance of sand-stones and flag-
stones is a question of selection. In
those which consist almost wholly of

silica, the durability is very great. Some
of these stones contain as much as 98
per cent, of silica. A tomb of this ma-
terial is cited which was erected in 1646,
and ordered by the Scottish Parliament
to be defaced in 1662. The original
chisel-marks are still fresh on the surface
of the stone (as in the case of the scutch-
eons at Naples), on which the lapse of
200 years has produced little effect, ex-
cept that of somewhat roughening the
exposed faces on the west and north
sides.

In cases, however, of striated or colored
sandstones, destruction goes on by so-
lution of the cement or matrix in which
the particles1 of silica are embedded.
The most common kinds of matrix are
clay, carbonates of lime and of iron, and
the hydrous and anhydrous peroxides of
iron. In one case of a stone of this kind
an inscription, cut in 1863, is no longer
legible. We should like to know the
depth to which the letters were originally
cut ; J in. at least has been removed from
the stone in sixteen years, which is at
the rate of nearly } in. in a century.

The well-known propriety of the rule
for setting stone on its natural bed is
illustrated by the degradation of lamin-
ated flagstones when set on edge. Dr.
Geikie cites an instance in the case of
stones thus treated of the loss of J in.
in thickness in forty years, which rather
exceeds f in. in a century. A curious
instance is also given of pillars of a con-
cretionary sandstone, which exposure to
the air for 150 years has hollowed out
into positive troughs, with hollows from
4 in. to 6 in. deep, and from 6 in. to 8
in. broad.

As to granite, we are referred to the
experiments of Professor Pfaff, of Erlin-
gen, described in the Allgemeine Geolo-
gic als exacte TTissenschaft, p. 317, on
granite, syenite, Solenhofen limestone,
and bone. From the limestone the Pro-
fessor found the loss to amount to the
removal of a uniform layer of 0.04 milli-
meter in three .years, which gives 0.52 in.
in a century. The annual loss of granite
he estimated as 0.0076 millimeter per year
from unpolished, and 0.0005 millimeter
per year from polished surface. This dif-
ference of more than 10 per cent, against
the latter is contrary to what would have
been expected ; and it has to be asked
for what period of time the more rapid

AS TO THE DURABILITY OF BUILDING STONES.

429

weathering is supposed to continue.
The slower rate amounts to 0.30 in. per
century. Granite has been employed
monumentally in Edinburgh for too

short a time to allow of the measurement ;
of its rate of decay there. But in con-
nection with the subject we may be al-
lowed to recall remarks made in the
columns of the Builder nearly twenty
years ago on the subject of the rough
and granulated surface of the granite on j
the west face of Waterloo Bridge. The
arches and exterior face of that bridge
are built of Cornish granite, from the
vicinity of Penryu, and the balustrade is
made of fine grey Aberdeen granite.
A careful and exact admeasurement of
the projections of this bridge, compared
with the original dimensions, would en-
able the student to arrive at a correct
estimate of the rate of weathering of
these two kinds of granite in London.
The bridge was opened in June, 1817.

The close of this interesting specimen
of the " Geological Sketches " of Dr.
Geikie refers to the fact that in the
towns and villages in the north-east of
Scotland, where the population is sparse,
and where comparatively little smoke
passes into the air, the marble tablets
last longer than they do in Edinburgh,
but still show everywhere indications of
decay. They suffer chiefly from super-
ficial erosion, but cases may be observed
of curvature and fracture.

In contrast to the perishable character
here ascribed to granite, to marble, and
to any but the purest silicious sand-
stone, is the durability of the humble
material, clay slate. This is employed
for monumental purposes in Aberdeen-
shire. It contains cubes of pyrites,
which might have been anticipated to
prove sources of destructive chemical
action, but which seem to be inert. The
stone is easily dressed in thin smooth
slabs. A tombstone of this material
erected in the old' burying-ground at
Peterhead, between 1785 and 1790, re-
tains its lettering as sharp and smooth as
if only recently incised. The stone is
soft enough to be easily cut wit j a knife.
The cubes of jyyrites are covered with a
thin film of brown hydrous peroxide.
The slate is slightly stained yellow
round each cube, but its general smooth
surface is not affected. While neighbor-
ing marble tablets, 100 to 150 years old,

present rough granular surfaces and
half-effaced inscriptions, the lapse of
nearly a century lias produced scarcely
any appreciable change upon the clay
slate.

The durability of this material, when
prepared by nature for the stone cutter,
may be compared with that of the even
humbler, but equally durable substance
of artificially baked clay. In the dry
and frostless air of Egypt, marble and
granite are almost perennial in their du-
ration. But the main revelation of the
forgotten history of the past is derived
from the baked clay inscriptions of
Assyria. The inertness o£ this sub-
stance, its hygrometric resistance, and
feeble chemical affinity with any element
with which it comes in contact, is the
cause of its indifference to the passage
of time, or rather to the recurrence of
those changes of temperature and of
moisture which accompany the revolution
of the year. If the value of clay slate,
as a material for monumental inscrip-
tions, had been better and larger known,
how much would our churches and
churchyards tell, which is now wholly
unrecorded %

The chief cause of the interest which
we took, from the first hint of this pub-
lication that reached us by chance, in
these researches of Dr. Geikie, was the
hope that they would throw some definite
light on what we regard as the most
difficult, and one of the most interesting-
questions relating to any monuments in
Europe, viz., the age of Avebury and
of Stonehenge. Nor are the remarks
without direct bearing on that subject.
The stone known as " Sarsen " fulfils the
requirements above shown to be con-
ducive to the most permanent dura-
bility. It is compact, uniform, close-
grained silex. We cannot cite any
chemical analysis of the stone. But we
do know that the Wiltshire farmers have
found it so indestructible by the usual
instruments of agricultural violence, that
they had recourse to the barbarous plan
of roasting these priceless monoliths,
heaping faggots on them to make a bon-
fire, and then throwing on cold water to
crack the stones ! This argues wonder-
ful resisting power in the "Sarsen," and
no one can be familiar with the stone in
question without seeing that it affords
I the least possible advantage to the tooth

430

VAN NOSTRAND'S ENGINEERING MAGAZINE.

of time. Time, indeed, as Dr. Geikie
observes, is not an agent, except indi-
rectly, in the matter. Mere duration
from day to day has little or nothing in
it that is destructive, as we see in Egypt.
It is because the revolution of the year,
and the succession of the seasons, expose
a monument to the successive and ever-
repeated attacks of rain, of frost, of per-
haps the scoring draughts of well-driven
sand, and because the incessant repetition
of these small causes of decay produces a
great accumulated effect, that we regard
times as destructive. But too much at-
tention cannot be given to the consider-
ation that it is the action of severe frost
on stone* containing water that is the
main cause of decay. And we venture to
suggest, as a subject for careful chemical
analysis, how far the existence of water,
or the elements of water, not as moist-
ure, but as chemically combined with
lime, magnesia, or other elements, in a
stone, may render it susceptible to the
attacks of frost. That idea is, perhaps,
a new one ; but we feel certain that the
hygrometric relations of marble and
compact limestones are not by any means
clearly understood,. The effect of frost
on these stones has been shown. This
view of the case makes it the more nee
essary to repeat and to comprehend the
experiments of Professor Pfaff on gran-
ite. In anticipation, any one would have
said that polished granite would be the
most durable ; and the idea that it would
most thoroughly throw off the rain, and
thus escape soaking and subsequent
frost -splitting, concurs with this antici
pation. If the case really prove to be
the reverse, we can see no explanation
for it, except in the possibility of the
bruising of individual molecules of feld-
spar in the process of polishing, so as
to make them more readily absorbent.

But this is a subject that will repay
the most careful experiment.

As to the Wiltshire monoliths, we
think that the whole inquiry above men-
tioned points in the direction of their
immense antiquity. The only chance, so
to speak, of Time for attacking them is
when they are so set as to expose the
ends of what really is, though not visibly,
the bed-course. Those who know Ave-
bury will remember themarks of decay on
some of the 18-ft. monoliths that form the
sides and roofs of the cellse. The infer-

ence, seen from the light of the Edinburgh
observations, points to enormous age.
Let us add that, at a distance from the
spot, we have no means of determining
the chemical constitution of the " blue
stones " in the inner ring of Stonehenge,
or their present condition as compared to
that of their giant brethren in the trili-
thons. Here is a subject for careful ob-
servation, analysis and record. And it may
prove that a comparison of the chemical
constitution and lithological condition of
these two kinds of stone may enable the
man of science to construct something
of an archaeological calculus that will
throw light on the date of Stonehenge.

REPORTS Of ENGINEERING SOCIETIES.

American Society of Civil Engineers. —
The latest issue of the Transactions con-
tains :

Paper No. 242. — On the Overflow of the Mis-
sissippi Riv^er. By Lyman Bridges.

Paper No. 243. — High way Bridges. By James
Owen.

At a meeting of the Society held Wednesday,
Sept. 20th, a paper describing the methods
used in a rapid topographical survey of a por-
tion of the Gold Field of Nova Scotia, by Wm.
Bell Dawson, was read in the absence of the
author by the Secretary. This survey was made
by the use of stadia hairs and a Rochon mi-
crometer telescope for the measurement of dis-
tances and resulted successfully and with very
moderate expense. Col. Wm. H Paine, Vice
President of the Society, described the methods
in use by him in making surveys for the cam-
paign maps of the Army of the Potomac during
the war, observations often being taken from
the tops of trees and the resulting maps show-
ing remarkable accuracy. Mr. Robert B. Stan-
ton, M. Am. Soc. C. E. of the U. P. R.R., also
described rapid surveys made by Mr. Blickens-
derfer and himself in preliminary reconnoisances
for the Pacific Railways.

ENGINEERING NOTES.

ENGINEERING STRUCTURES IN ITALY. — A
paper was prepared lately by Signor C.
Clericetti on the " Great Structures erected in
Italy during the last Twenty Years."

The author chooses the bridges of iron and
stone erected during the last twenty years as
the structures which best exhibit the progress
of engineering science, and he compares these
modern bridges with those built by the Romans.
The characteristics of these latter are grandeur,
massiveness, and durabilty; of the former,
lightness, economy, and rapidity of construc-
tion.

The Po between Pavia and the sea was never
bridged by the Romans, but during the last
twenty years four bridges have been built over
it. The lengths of these bridges are 577, 762,

ENGINEERING NOTES.

431

427, and 400 meters; 1,900, 2,000, 1,399, and
1,812 feet respectively; the spaus varying
from 213 to 250 feet. They are all girder
bridges, BUpp<>rted Oil piers founded at depths
of from GO to 70 feet below highest flood level,
and formed of iron cylinders sunk by hydraulic
process.

To show the difference between the ancient
and modern systens of construction the author
compares the Roman bridge across the Danube,
one of the boldest of their works, with the
modern structures on Ihe Po. The former —
1,20T meters (3,960 feet) in length— had twenty-
one wooden arches of 50 meters(164 feet) span;
and the piers — founded on a masonry platform
extending right across the river bed — had a
thickness of 17.7 meters; while the piers of the
latter, though 28 meters high from the founda-
tion, are less than 3 meters thick at the top.
The ancient piers had six times the thickness
required for a modern girder bridge, and three
times what would now be allowed for masonry
arches of 50 meters spau. The same immense
piers were built throughout the middle ages ;
the old bridge at Verona, for instance, with
two arches of 21.54 meters and 48.70 meters
(93J£ and 160 feet), has a pier 12 meters thick,
though only 3.50 meters high.

The author proceeds to point out the superi-
ority of the modern system of long spans and
narrow piers, in leaving the channel free for
navigation and the discharge of floods, and
avoiding the scouring action caused by ob-
stacles to the natural flow. In some cases old
bridges have so impeded the flow as to cause
serious inundations above bridge.

The author states that, with few exceptions,
only one type of bridge — the lattice-girder — is
constructed in Italy, and regrets that little en-
couragement is given to improvements in de-
sign. He mentions a few arched bridges,
among them being that over the Celina torrent,
which-he considers one of the best examples.

The author proceeds to discuss the sub-
ject of the incalculable strains to which
bridges are liable ; from the points of support
not being knife edges, as theory supposes;
from the vibrations in cross sections; from the
vibration caused by passing trains, &c. Airy
attempted to ascertain the strain in a bar of
iron from its musical note, but the result was
not satisfactory. Better results are obtained
by instruments for measuring the contraction
and elongation of bars daring strains, such as
the apparatus of Dupuit and Manet in France,
and (Jastigliano's multiple micrometer, which
the author describes.

The experiments made with Dupuit's appa-
ratus upon all kinds of girders show that the
actual maximum strains are in general less than
the calculated, particularly in arches and in
the horizontal members of straight girders.
Iron bridges are also exposed to danger from
corrosion, but the author states that Mallet's
experiments proved that an iron bar 6 milli-
meteis (0.238 inch) in thickness wouid not be
destroyed in less than 700 years.

The author then gives particulars of some of
the principal brick and stone bridges recently
erected. Comparing modern with ancient
structures, he points out that the former are

built with one-third less material than the
hitler. In ancient structures the ratio between
the thickness of the piers and the span varied
from one-fourth to one-halt, while in modern
it has been reduced to one-sixih, and even one-
seventh. The average ratio between the thick-
ness of the arch at the crown and the span was
0.086, while in modern bridges it is from 0.040
to 0.031.

The two principal arched bridges erected in
Italy during the last few years are the
Poute Annibale and the Ponte del Dia-
volo. Each of them has a span of 55 meters
(180 feet), and thickness at the crown of
2 meters, the versed sine of the former being
14 meters, of the latter 13.55 meters. Circular
openings 9.25 meters in diameter are intro-
duced to lighten the haunches. These are the
largest masonry arches in the world, with the
exception of one at Chester of 61 meters span,
and one on the Washington Aqueduct in
America of 67 meters. In the year 1370, how-
ever, an arch of 72.25 meters "(237 feet) span,
and 20.70 meters rise, was erected over the
Adda, at the Castle of Trezzo. This arch was
considered the eighth wonder of the world, both
for size and for the short space of time — seven
years and three months — occupied in its con-
struction. The Ponte Annibale and the Ponte
del Diavolo were built in twelve and ten months
respectively. Among recent improvements in
deiail the author mentions the use of hydraulic
lime and cement, which allows the centers to
be struck very shortly after the completion of
the arch; and the use of sandboxes instead
of wedges for slacking the centers, a system
which he strongly recommends. — Architect.

rpHE Channel Tunnel. — At the meeting of
JL the Paris Academy of June 26, M. Daubree
read a note on the geological conditions of the
Channel tunnel. The works connected with
the tunnel comprise three phases: — (1) Scientific
researches; (2) preparatory works; (3) execu-
tion of the tunnel itself. The first phase was
devoted to purely geological investigation, in
the form of minute exploration of the French
and English coasts, exact and detailed investi-
gation, of the sea-bottom in the Strait, borings
made on terra fir ma which verified the nature,
thickness, and inclination of the strata, and
gave an approximate idea of the hydrological
condition. Since 1879 the second phase has
been entered on by verifying the previous
scientific data, and preparing for the execution
of the tunnel itself, experimenting in small
galleries with machines and tools capable of
being ultimately used in a work of exceptional
importance. On the French coast, the geo-
logical investigation established a slight bulg-
ing of the beds at the place known as the
Quenocs. On account of this bulging the in-
clination of the strata, which, in the strait is
towards the north-north east, is found, along
the cliffs of Blanc Nez, turned towards the
south-east, and the slope which, according to
; the first orientation, in the neighborhood of
the Quenocs, is about 0.05 per meter, is found,
in the second, to be nearly 0.09 m. It is im-
portant then, to find in what conditions this
| bulging may modify the physical conditions of

432

van nostrand's engineering magazine.

the banks forming the base. of the Rouen chalk.
For this purpose the French Association had
dug, near Sangatte, two shafts of a depth of
86 m., which met the gault at 59 m. below the
hydrographic zero, adopted in the maps in
which the geological explorations of 1875-6 are
recorded. The digging of these shafts, one of
them 5.40 m. in diameter, showed that all the
white chalk and the upper part of the Rouen
chalk are water-bearing. These strata had
thus to be abandoned

On the other hand, the base of the Rouen
chalf allowed only a very small portion of
water to pass. There, then, the tunnel should
be pierced, as the stratum appeared to proceed
without interruption from France to England.
The water penetrating the works is fresh, and
of good quality; at the upper part only some
slightly salt veins were found. Nevertheless,
the communication of the water-bearing strata
with the sea is proved by the oscillation of the'
water-level in the shafts according to the tide,
and by the invariable increase at high water.
M. Daubree then refers to further galleries dug
on the French and on the English sides, and
excavations made with the machines of Col.
Beaumont and Mr. Biunton. On the Dover
side, the chalk, which on the French side was
but little permeable, was, on the English side,
quite impermeable. Oving to this circum-
stance, they were able to beiiin at the bottom
of the shafts, at 29 m. below the French
hydrographic zero, a gallery advancing under
the sea by following in the stratum an almost
regular descending slope of one-eightieth, or
12.5 mm. per meter. The bgd on the English
side, somewhat more powerful than on the
French side, presents a very great regularity.
Thus the Beaumont machine, which has been
used in the perforation, has been easily able to
trace a perfectly cylindrical gallery, which has
now reached 1,800 meters from the shafts, of
which 1,400 meters are under the sea. So far
there has been no access of water. In the banks
which form the base of the Rouen chalk, the
rock in mass is almost completely dry; the ac-
cess of water which has been observed has en-
tirely the character of small springs issuing
from the joints of fracture or cleavage. The
perfectly cylindrical form produced by the
Beaumont machine renders the gallery where
such leakage occurs easily isolated by means of
cast-iron rings prepared in segments easily
united, the rin^s themselves being clamped to-
gether to form a tube of any length. When
the water spurts out in considerable force, a
sort of mastic or minium is successfully em-
ployed, which is placed between the segments
of the rock, and compressed in the manner of
a water-joint by the pressure of the rings
against the rock. The mastic also seems to
render the joints of the neighboring rings
water-tight. Owing to the excellent make of
these rings, they can be rapidly put in position ;
a complete ring can be placed in half an hour,
and several experiments in the Shakespeare
Cliff Gallery have proved that by this simple
process the springs encountered can be com-
pletely blocked. On account of the slope on
which the English gallery descends, its ex-
tremity recently reached 51 m. below the hy-

drographic zero, at a point where the depth of
the sea at low water is 5 m. ; there is thus 46
m. of chalk between the floor of the gallery
and the bottom of the sea.

Proposed Tunnel Under the Elbe. —
Under the river Elbe, at Hamburg, it
has been proposed to build a tunnel to connect
that city with an island a third of a mile distant.
The great Hanseatic city, which has hitherto
been a free port, is shortly to lose that privilege,
and to be included in the Zollverein or German
Customs Union. It is intended, however, to
make an exception in favor of the island in
question, which bears the name of Stein-
warder, and to permit it to retain the privileges
of the free port. Large bonded warehouses
will be built there for the accommodation of
merchandise before paying duty, and in order
to bring the island into closer connection with
the city, the above-mentioned scheme for a
tunnel under the river has been started. The
tunnel would be 500 meters or nearly a third of
a mile in length. This will be upwards of 300
feet longer than the Thames Tunnel. The cost
of the Elbe Tunnel is estimated at about
£900,000.

^T^he Largest Lock tn the World. — It
JL will be of interest to all those who either
support or oppose the scheme for a ship canal
to Manchester to know what is, at present, the
largest lock in the world. In a statement re-
cently submitted to the Congress of the United
States this is said to be on the St. Mary's Falls
Canal. " The canal is slightly over one mile in
length. There are two locks to overcome the
same elevation, one being the largest in the
world. It is 515 ft. in length, 80 ft. wide, and
18 ft. lift." The estimated yearly expense of
working it is $25,000. On the Lousville and
Portland Canal, which is 2.15 miles long,
are two locks 372 ft. long and 80 ft. wide, with
12 ft. and 14 ft. lift-. These locks were
worked by hand in 1879; 3,168 vessels of all
classes passed through the canal in that year.
A tow-boat, a dock, and steam dredges are
maintained. The expenses for 1879 were
$30,928, of which $14,453 were for dredging.
The North Sea Canal is stated in the. same re-
port to be sixteen miles in length, and from 130
ft. to 400 ft. in width. The level is below that
of the sea. There are two sets of locks of
large dimensions, and an artificial harbor
constructed under great difficulties. The
depth, originally 23 ft., is to be increased to
26 ft. by 1884. The cost of the work was
$10,800,000. From November, 1877, to August,
1879, 4,862 vesssels passed through the canal.
The working expenses for the only year for
which they have been obtained were $75,569.
There are eight miles of canal to each lock -lift.
On the Des Moines Canal, 7.6 miles long, there
are three locks, suitable for the longest
steamers on that river. The annual expenses
are above $30,000, including a large amount
for dredging. A detailed estimate of the num-
ber of minutes occupied in each of the eight
operations involved in the process of going
through one of these large locks amounts to
20£ minutes. At St. Mary's Falls the ap-
proaches are not completed, and cause material

KAIL WAV NOTES.

433

delays, yet lockages do DOt OCCUpy half an

hour each. The reporter concludes thus:—

Probably, in almost every location where water
is to be had, a better ship-canal can be made
with a few locks, and at a far less cost than the
sea level canal. A small part of the money
saved by the locks will, in most ea-es. make a
broad and deep canal, where ships can go
safely and rapidly, and pass each other any-
where without delay; instead of narrow deep
CUtS, commonly dangerous and always expen-
sive, where ships must move slowly, and wait
to pass each other. The question must be de-
cided in each case whether the large amount
required for the construction of a lock will save
a larger amount some other way, and whether
the delay at each lock will save a greater de-
lay in some other way.

RAILWAY NOTES.

ACfieap Railway. — There is now7 at work
an interesting miniature railway — five
miles in length — which unites the village of
Westerstede in East Frisia with the station of
Ocholt, on the Oldenburg and Seer line. It is
solely due to the enterprise of the thinly-scat-
tered population of the district, and carries
their cattle and other produce to market, bring-
ing them back their few requirements. The
soil is marshy, so that a good deal of drainage
work had to be done, and it was necessary to
carry the line above the level of the frequent
floods. In spite of this, the cost of construc-
tion was only £2103 7s. 6d. per mile ; and the
cost of working (including wages, fuel and
every expense) amounts to the magnificent total
of £1 7s. 6d. per diem. The buildings consist
of a shed at each end of the line ; the ternr-
DUS is the courtyard of the principal inn at
Westerstede, and the single station — half way
along the line — is the house of a gentleman,
who ho>pitably entertains the passengers while
they are waiting for the train. The rolling
stock comprises two small four-wheeled tank
locomotives, weighing (when in working order)
74 tons each ; three carriages, of the American
type with a door at each end ; two open goods
trucks and two covered. A train consists of
the engine and two vehicles, between which
the guard sits. There are no turn-tables, so
that the locomotive is at the hinder end of the
train in returning. The fuel employed is turf,
which is abundant in the district. The receipts
of this tiny railway are steadily increasing. —
Engineering.

At a recent meeting of the American Mas-
ter Car Builders' Association the Presi-
dent suggested for discussion : " Is it safe to
run a journal under passenger trains after it
has been heated sufficiently to burn out the
packing and cooled off with water ?" Mr. Bis-
sell said : It is usually the case that new cars
ruuning out of the shop will run warm if ever.
Sometimes it will be so warm as to discolor the
paint on the box and spoil it. I think it is very
seldom the case that they take those journals
out that heat up. The President said : Car-
builders, as a rule, pack their boxes very shab-
Vol. XXVIL— No. 5—30. *

bily, and they almost always ^et hot ; but they

are very Beldom allowed to get hot enough t<>

burn the packing OUl and to be cooled oil' with
water. 1 have taken great intercsl in Irving to
learn what was the cause of journals breaking
off at the shoulder, showing do fracture, while
the center of the axle would show a remarka-
bly good quality of iron. A few days since I
was testing some axles, and (luting the test 1
put under a few old axles, ami at the BeCOnd
blow on one of them the journal Mew ©fl into
the air I should say ten feet or fifteen feet,
simply with the jar of weight dropping upon
the axle. The axle was tested with a 1600-lb.
drop, and, in order to find out the quality of
irou in the axle, I concluded to break it, and if
my memory serves me, I would drop that
ltfOO-lb. weight fifteen feet, reversing the axle
each time seven times before we broke the
axle. Now the journal showed no fracture of
any description. It was completely crysialized,
and I am very strongly of opinion thai that
was caused by meeting, in the first place, a

j cooling off with water under load, and I am
so thoroughly satisfied on that point that my
instructions are 10 remove every axle that has
been heated sufficiently hot to be cooled off
with water. I have seen several instances

! where the journ.al dropped off and was found
iu the box and the car came in safely. In fact
one or two of the Pullman cars have come in
with the journal lying in the oil-box. While I
don't doubt that the axles were of good mate-
rial, I firmly believe that an axle, after it has
been heated sufficiently hot to burn the packing
out and cooled off under load, is an unsafe
axle ; and by microscopic examination of the
journals that drop off in that way, you will ob-
serve that there is a yoke very otten the whole
distance round the axle at the shoulder, show-
ing that under load the journal bent as it re
volved. — Engin eer.

Steam Tramways in London. — The Lon-
don Street Tramways Bill, notwithstand-
ing considerable opposition, has passed through
committee in the House of Lords, and thus the
thin edge of the wedge for the introduction of
steam as a moving power for tramways in
London has been successfully inserted. The
bill provides for the construction of a tramway
along the Pentonville Road from the Angel,
Islington, to King's Cross. Pentonville Road
having a very steep gradient, the cars will be
driven by stationary engines placed at several

I points on the line, on a principle already in
use in America, that is to say, by wire ropes

! passing under the permanent way. We are
sorry to see this, although the tramway itself
will be of very great convenience, completing
the link that was much wanted between the
Great Northern and Midland Railways and the
tramways which branch from the Angel,
Islington, to the north and ea^t. But the
nuisance which will arise from stationary en-
gines to the neighborhood will be intolerable.
Lords, and, for that matter, Commons, how-
ever, do not reside in the North or East of
London. We are sure they would never per-
mit the introduction of steam tramways in the
fashionable quarters of the West. — Iron.

434

TAN NOSTRAND'S ENGINEERING MAGAZINE.

The Electric Railway in Ireland. — The
works in connection with the electric
tramway between Portrush and Bushmills,
County Antrim, says the Glasgow Herald, are
now approaching completion, and it is ex-
pected that the line will be formally opened for
passenger, goods, and general traffic by the
Lord Lieutenant early in August. Electric
tramways have been already worked success-
fully in Berlin and in Paris, but to County An-
trim -will belong the honor of having intro-
duced the new motive power for the propul-
sion of carriages and wagons within the United
Kingdom, and 50 years hence the six miles of
railway leading to the Giant's Causeway may
share the historic interest of the line between
Stockton and Darlington. The new scheme is
to be considered from two points of view — the
scientific and the financial. Viewed from the
former standpoint, the new tramway presents
several novel features of construction. The
line, instead of being laid along the center of
the roadway, is placed upon the side of the
road, on a " trampath," from which the ordin-
ary road traffic is excluded, but which suits as
a footpath when so required. At the Portrush
terminus is a building for the engine and dyn-
amo-machine which develop the electricity, the
patent adopted being that of Siemen. The
rails are made of the best steel, and, no heavy
engines being required, will be subjected to
comparatively little wear and tear. The cars
are also of the lightest construction, and fric-
tion will be reduced to a minimum. The pro-
ject, looked at from a financial point ofcview,
gives every prospect of success. The tramway
will communicate both With the quays and
with the railways at Portrush, and, besides the
passenger tariff, several sources of revenue are
already assured, including the carriage of
goods and animals, iron ore and limestone. In
addition to the indirect gain resulting from
diminished deterioration of rolling stock and
permanent way through decrease in friction, it
is estimated that the cost of working the new
line will amount to only one penny per mile
as compared with seven pence per mile for
steam-power, and eleven pence for horse-power.
One large item of profit arises from there being
no need of engine-drivers and stokers, the con-
ductor being able, unaided, to regulate the
movements of his car. Finally, the cost of
construction has been greatly kept down from
the company having themselves carried out all
the works in connection with the line. — En-
gineering News.

IRON AND STEEL NOTES.

Art Castings in Iron.— A new departure
of great interest has recently taken
place in iron founding. This is the reproduc-
tion of various art works in iron castings.
Shields ornamented with repousse work, hel-
mets ornamented in relief, medallions, plaques,
and Japanese bronze trays have been used as
patterns, and successfully copied.

The work has been done in an iron foundry
in Chelsea, Mass. The most delicate patterns
have been successfully followed. One large

shield represents the siege of Troy, and is a
copy of Cellini's shield. The numerous small
figures are brought out clearly, and defined
with precision. The shield is 22 in. by 28 in.,
and is colored to represent bronze. This
bronzing is produced by copper deposited by
electricity. Another shield, heart-shaped, and
22 in. by 26 in., depicts the conflicts between
Jupiter and the Titans. This has the natural
color of the iron. Two circular shields show
Bacchus armed with the thrysis and accompa-
nied by a leopard. A triumphal procession is
represented on a large salver. A copy of a
bronze plaque with a head of Shakespeare and
a reproduction of some repousse work after
Teniers are also to be seen.

A helmet elaborately ornamented with intri-
cate designs has been reproduced from a cast-
ing made at the Ilsenburg foundries, in Prus-
sia. Many fine castings have been made there,
but there has been no attempt at classical art
in the designs employed. Some antique swords
with curious hilts accompany the helmet. Even
more interesting are the reproductions in iron
of two medallions. One is a profile portrait of
F. D. Millet, by Augustus St. Gaudens, and
the other is the portrait of a young lady. In
both the iron is bronzed. There are two small
panels in iron, which have boen "buffed"
until they look like steel. One bears an ex-
quisite chrysanthemum with its delicate grace
preserved in the prosaic medium in which it
finds expression. The other bears some leop-
ards taken from antique bronzes.

A Japanese lacquer tray, with fine ornamen-
tation, has also been reproduced in iron only
a sixteenth of an inch thick. A medallion,
with a head of Apollo in alto relief, is as strik-
ing as the foliage and flowers that have been
executed in low relief. The bronze castings
resemble beaten work in copper.

There are no especial peculiarities about the
production of these castings. American iron
is used, the moulds are of fine sand, and the
best workmen and the greatest care are em-
ployed. The "facing" of the moulds is of
dust from the beams of the foundry. Impres-
sions are secured in the sand of the shield or
panel to be cast, and the mould formed in the
usual way. The casts are put under a rag-
wheel with emery to prepare them for plating.
The work has been treated in different ways,
being polished to show the color of the metal,
bronzed, copper-plated, and oxidized, simply
that varying effects might be studied. The
experiments have proved that remarkable firm-
ness can be obtained successfully in work in
iron, and the art castings will now be p.laced
on a commercial basis.

The first work done in this direction was by
the same company in 1876, when plates were
cast from compression bronze patterns. About
two years ago the matter of art casting was
taken up, in connection with an attempt to in-
troduce artistic work into the ornamentation
of stoves. One advance led to another, until
in the course of time the production of these
art castings followed.

The attention of architects and interior deco-
rators has been attracted already. For plaques
to be hung upon the walls these reproductions

ORDNANCE AND NAVAL.

435

are rather heavy. But ■ ready use is expected
for iron panels, reproducing repousse or other
Ornamental work, to he used in dcon, in furni-
ture, on the fronts of the steps, in BtairwayS,
or in fireplace linings. Original patterns, of
Course, Can be employed. Panels may also be
used in friezes and dados and in a great variety
of decorative forms. A more directly archi-
tectural use of artistic iron castings is in balus-
trades and railings. Compared with bronze
work, beaten by hand, the eost of these iron
castings is very slight. An estimate was made
that the reproduction of an elaborate bronze
salver, with repousse work, in bronzed iron
could be sold at a profit for ten cents a
pound.

The Influence of Manganese on the
Stbbnotb of Iron. — By Dr. H. Wed-
. Prof. Finkkner, and Prof. Spangen-
berg. — A* prize of £100 having been offered
by the Society for the Encouragement of In-
dustry in Prussia for the best series of alloj's
of iron and manganese, two manufacturers
submitted samples, the examination of which
is detailed in this paper. According to the
conditions of the competition twenty rods of
iron were to be sent in, ten of an alloy of iron
and manganese with less than 0.6 per cent,
carbon, and not more than 0.4 per cent, im-
purities; and ten of an alloy rich in car-
bon, and in which the impurities were not
to exceed 0 6 per cent. The proportion of
manganese in the first series of samples was to
increase gradually from 0.5 to 5 per cent.,
while the amount of carbon in the second
series was to vary by increments of at least
0.15 per cent. The rods or bars were to be
perfectly homogeneous, and 50 centimeters
(19.685 inches) long by 40 millimeters (1.575
inch) thick.

The chemical examination, which included a
careful analysis of each bar, was carried out
by Professor R Finkener, while the mechani-
cal tests were entrusted to Professor Spangen-
berg. The analyses of the first ten bars
showed that the proportion of manganese va-
ried from 0.42 to 0.88 per cent., while that of
the carbon was from 0.36 to 1.94 per cent.
The second series of ten alloys by the same
maker were found to contain carbon in pro-
portions varying from 0.29 to 0.74 per cent.,
instead of the stipulated minimum of 0.6 per
cent. The percentage of manganese rose from
0.24 to 4.37. The first series of samples sub-
mitted by another firm contained : manganese,
0.32 to 11.4 per cent. ; carbon, 0.58 to 2,42 per
cent.; maximum impurities, 0.92 per cent.
The second series showed a gradual increase of
manganese from 0.35 to 2.21 per cent., the
amount of carbon rising at the same time from
0.58 to 2.9 per cent. From these analyses,
which are given in detail, it appeared that none
of the competing series completely fulfilled
the prescribed conditions with regard to chemi-
cal composition. It was found in carrying out
the physical experiments with these alloys that
they were extremely hard, and so brittle that
they frequently flew into numerous pieces when
subjected to a transverse strain. The tensile
strength did not appear to bear any fixed rela-

tion to the amount of carbon or manganese

present, and in many cases the alloy was not

homogeneous. The impurities, especially the

phosphorus, contained in the samples tested
may have had more influence on the mechani-
cal results man either carbon or manganese. —
Abstract qf Inst, of Civ. Bng.

ORDNANCE AND NAVAL.

rrinE Monchieff System of Protected

JL Barbette. — Colonel Moncrieff has ad-
dressed the following to the Timtx on this sub-
ject : All the reports of the Moncrieff battery
at Alexandria that I have seen go to confirm
the opinions generally entertained regarding
the system which it represents. I do not know
how far my principle was complied with in the
profile of this particular battery ; while, how-
ever, the other batteries were reduced to ruins,
their guns dismounted, and the men blown to
atoms by the terrible artillery fire to which
they were exposed, the solitary Moncrieff bat-
tery, although receiving a full, if not a greater
share of the attack, remained a perfect shelter
for the men working it, and was fit for action
to the last. I trust that this result will lead to
the further development and application of my
system. The English authorities, through my
agency, have in recent years developed the sys-
tem thoroughly for siege artillery, with the
best results ; and, at the recommendation of
the committee which was entrusted with the
experiments, Moncrieff siege carriages have
been adopted in the service, as well as those
for permanent works, and it is to be hoped
that an opportunity will also be afforded to
test their advantages in the field. But the
authorities have declined many applications
from me to be allowed to use the system for
18-ton and heavier guns for coast defence, it is
thus restricted to land service guns up to the
weight of 12 tons. Its value for coast batteries
is thereby almost lost. It is my opinion that
the system which has worked so well with the
siege carriages is better suited for 18-ton and
heavier guns than for the lighter guns to which
it is actually applied. This opinion has been
frequently expressed, and many designs and
proposals submitted for carrying it out. I
would desire to direct the attention of the ser-
vice to the long delay in applying the system
to land service guns above 12 tons, in the hope
that opinions may be formed and expressed at
this time which may induce the authorities to
resume the application of the system for
heavier artillery, for which everything is ready
except permission to begin. When the time
arrives for using our defences, I am certain
that it will be regretted that this system is not
applied in ihose positions inwhich it is admit-
ted to be the best that can be used, and that
the recommendations of the numerous commit-
tees which have recommended its application
to them on the double grounds of economy
and efficiency have not been carried out. It
may now be said that the reports of these com
mittees are predictions of what has actually
happened at Alexandria. It is now some time
since I exhausted all my means of pressing this

436

VAN NOSTRAND S ENGINEERING MAGAZINE.

matter. I trust that others, on public grounds,
may now come to my aid iu urging the import-
ance of the subject, and in having the system
applied to heavier guns on our coast defences.
Recent events have proved it to be able to re-
sist naval attack, and it only requires to be
applied to heavier artillery lo make it available
in many positions which would at once become
much more formidable by its application.

Compound Armor -Plat « T rials. — Fur-
ther experiments at Portsmouth confirm
in a marked manner, says the Time*, the extra-
ordinary results previously obtained from com-
pound (steel-faced) armor. The admiralty hav-
ing increased the severity of their tests on
board the Nettle by the introduction of a 10-
inch gun, one of Sir John Brown & Co.'s
Colling wood armor-plates, manufactured on
the Ellis principle, was fired at on July 11.
Having in the meantime been removed from
the target, it was examined recently for the
purpose of ascertaining the effects of the or-
deal upon the iron backing.. The dimensions
were 7 feet 9 inches by 5 feet 10% inches by 11
inches. The plate had been previously fired at
with the 9-inch gun under the u^ual conditions
— viz., three rounds with 50 lbs. of powder
and 260 lbs. chilled shell, at a distauce of ten
yards. The first shot produced the low indent
of 3.7 inches without any crack, while the in-
dents of the second and third rounds were
4.4 and 3.9 inches respectively. Cracks were
produced by these shots, one extending to the
edge of the plate. The charge of the 10-inch
gun is 70 lbs. , and the weight of the projectile
400 lbs. The range was the same as with the
9-inch gun. The first shot was fired at the
right bottom corner, two feet from each edge,
and produced a clearly defined indent of 4.4
inches, and several cracks circumferential to
the point of impact. One of these reached to
the bottom edge, and extended through the
plate. The second shot was directed against
the left bottom corner, 19 inches from the side
and 23 inches from the lower edge, while the
third fell at the right top corner, 19 inches
from the top edge and two feet from the side.
Owing to the points of the shell remaining
fixed in the plate the depth of the indents could
not be measured. The bulges at the back
vary from f to | in height, and have not
opened out. Considering the severity of the
second test, and that there was hardly room
left for another shot, the damage effected was
slight, and the plate would still have afforded
efficient protection. The heavier gun seems to
have slightly pushed in the entire surface of
the plate within certain areas defined by vari-
ous injuries, but without showing any in-
creased penetration. In time the plate would
have been cracked through and through and
broken up under the severe cannonade; but it
is clear that not a splinter would have found
its way into the ship so protected. At present
we know the effect of the 9, 10, and 12%-inch
guns upon compound armor 11-inch plates, and
experiments which are about to take place at
Spezia will determiue whether 19-inch plates
can withstand the atack of the 100-ton cham-
bered gun fired pointblank at short ranges. As

this gun is considered capable of piercing iron
armor over 13 inches in thickness, the results
will be watched with the greatest interest.
The comparative thickness of the steel-faced
armor is an important factor in the trial. The
targets to be fired at at Spezia will consist of
two entirely steel plates, manufactured by
Schneider at Creusot, and two compound armor
plates by Messrs. Cannell and Sir John Brown
& Co., of Sheffield. Their dimensions are 9
feet by 12 feet, the compound armor having
steel surfaces one third of the whole thick-
ness.

New Ironclad. — A new armorclad, for
which the blocks have been some time in
readiness, is about to be laid down forthwith at
Portsmouth. She will be of the kind known as
the " Admiral " type and may be regarded to
some extent as an answering move on the part
of the Admiralty to the gigantic shipbuilding
projects of the Italian Government, While
the Bolney and the Howe exhibit certain im-
provements upon the design of the Cdlinguood,
the Camperdown, the name of the new ship,
will in her turn display various modifications
upon the design of the Rodney and Howe. She
will differ from the latter in being 5 feet longer,
having 400 tons greater displacement, and
carrying stronger barbe'te armor. Her dimen-
sions will be as follows: — Length, 330 feet;
extreme breadth, 68 feet 6 inches; mean
draught, 26 feet 9 inches; and displacement,
10,000 tons. She will be propelled by twin
screws, the engines being contracted to de-
velop with the use of forced draught 9,800
horses. It may be useful to contrast with
these data the measurements of the Duilio,
which are:— Length, 34l feet; breadth, 64 feet
9 inches; displacement, 10,434 tons; indicated
horse-power, 7,500. While, therefore, the
displacement of the English ship is slightly less
than the Duilio, her engine-power is consider-
ably greater, and is estimated to give her, in
spite of her broader beam,' a speed of 16 knots,
or two knots an hour more than the Italian
turret ship. She will be armored to the depth
of five feet below the water-line, and will be
protected by a belt rising 2 feet 6 inches above
the water-line. Her armor will consist of com-
pound plates of the following thicknesses —
On the side, 18 inches; bulkheads, 16 inches,
barbettes (normal), 14 inches and 12 inches;
conninff tower, 12 inches and 9 inches; and
screw bulkheads, 6 inches. She will differ
from all existing vessels, either armored or un-
armored, in having vertical ventilating 4tubes
extending from the flying deck to the lower
deck.' These tubes will be armored to the
thickness of 12 inches. She will be also pro-
tected by an armored deck 3 inches thick over
the belt and 2% inches thick below the water-
line at the ends, while the protection under the
base of the barbettes will be three inches.
Her armament is at present arranged to con-
sist of four 63-ton B.L.R guns, and six 6-inch
B.L R guns, besides a complement of boat and
machine guns and Whitehead torpedoes. Her
bunkers are to hold 900 tons of coal, and her
ship's company is intended to comprise 430
officers and men. The Camperdown will be a

M ISC KM. AN EOUS.

437

Bister ^liip of the Benbow, the contract for
which has just been accepted by Messrs. l'al-
mer Brothers, of the Tyne.

BOOK NOTICES.

Tu.ht. By Lewis Wright, London : Mac-
J millao&Co. Price" $2.00.

This is a hook for the experimenter and
Chiefly for the lecturer who employs the magic
lantern.

Beginning with a description of the lan-
tern an 1 its accessories, the author then de-
bes the common experiments illustrative of
reflection, refraction, dispersion, color, spec-
trum analysis, phosphoresence, fluorescnce,
interference aud polarization.

The work is illustrated with 190 woodcuts
and 7 full-page plates.

Though many of the experiments are not as

-factory as those by which they have been
of late replaced in this country, the book will
prove of considerable value to lecturers on
physics.

Geological Sketches at Home and
Abroad, bv Archibald Geikie, LL.D.,
F.K.S. Price, $1.76.

The records of geological rambles by one of
the foremost of living scientists possess a
value to scientific readers apart from the liter-
ary character of the essays. The present col-
lection, however, will be widely read by others
than scientists or students, who will be fully
repaid by the charming method by which the
author imparts an interest in things usually
passed by as uninteresting.

The key-note is struck in the first essay
wherein the author, under the title of "My
First Geological Excursion," describes his holi-
day rambles with his school-boy companions in
search of limestone fossils. The enthusiasm
awakened in those early days U manifested in
his latest essays. They are still holiday ram-
bles.

But when the reader is reminded that the
writer is the highest living authority in mat-
ters relatiuii to structural geology, and is, more-
over, Director-General of the geological survey
of the United Kingdom, he will regard the
pleasant narrative as authoritative statements
which will hereafter be counted as substantial
additions to our present knowledge.

Musical Acoustics. By John Broadhouse-
London: William Reeves. Price, $3.00

This work is designed particularly for stu-
dents of music, but will prove to be profitable
reading for students of physics.

Quotations from standard works are freely
used by the author; Helmholtz, Tyndall, Pole
and Sedley Taylor are each repeatedly drawn
upon at considerable length.

The subjects of Consonance and Dissonance,
Combination Tones, Consonant Chords, Scales
and Temperaments, are treated with excep-
tional fulness tor a hand-book.

The illustrations, more than one hundred in
number, are good.

r piN\i 1 1\<. —Explosive ( ompoi rds \m>

L ROCK DbilLB. By Henry S. Drinker.
Second edition, Revised and Enlarged New

York: John Wiley A: Sons. Price, $25.00.

The first edition of 1 his work became widely
known. It was published only four \ ear- since
and the edition was exhausted ;i year ago.

The author has taken advantage <>1 the op-
portunity to Carefully revise the Work and has

made some Important additions, relating chit lly
lO explosives, rock drills and air compressors.
Some valuable tables relating to drilling in
the Sutro and St. Gothard Tunnels, and also
some data relating to tunnels in India, will be
found among the new matter.

MISCELLANEOUS.

The following measurements of the great
lakes of America have been taken by the
Government surveyors : —The greatest length
of Lake Superior is 335 miles; its greatest
breadth is 160 miles; mean depth, C88 ft. ; ele-
vation, 627 ft. ; area, 82,000 square miles. The
greatest length of Lake Michigan is 300 miles,
its greatest breadth, 108 miles; mean depth,
690 ft.; elevation, 506 ft.; area, 23,000 square
miles. The greatest length of Lake LLuron is
300 miles; its greatest breadth is 60 miles:
mean depth, 600 ft. ; elevation, 274 ft. ; area,
20,000 square miles. The greatest length of
Lake Erie is 250 miles; its breadth is 80 miles:
its mean depth is 84 ft.; its elevation, 26 ft. ;
area, 6 000 square miles. The greatest length
of Lake Ontario is 180 miles; its greatest
breadth, 65 miles; its mean depth is 500 ft.;
elevation, 261 ft.; area, 6,000 square miles.
The total of all five is 1,265 miles covering an
area of upwards of 315,600 square miles.

Dr. Fleischer, of Germany, describes a
new system of hydraulic propulsion for
ships. He dispenses with a turbine, and allows
the steam to act directly upon the waier in two
large vertical cylinders placed amidships.
These two cylinders communicate with the
ejecting nozzles which are situated on either
side of the keel. In each cylinder there is a
j "float " or piston of nearly the same diameter
as the cylinder, with a closed spherical top;
when this float is in its extreme upper position,
; the cylinder is full of water. Steam is then
j admitted into the upper part of the cylinder
above the float, the latter is pressed down, and
j the water is expelled through the nozzle-pipe
j with great velocity. At a certain portion of
the stroke, the admission of steam is shut off
automatically, the remainder of the stroke
being performed during the expansion of the
I steam, and the velocity of ejection of the water
gradually diminishing. At the conclusion of
the stroke, the exhaust valve from the steam
space to the condenser is opened, the steam
rushing out, forming a partial vacuum above
the float, and the water enters, pres-ing the
Anal up.

A valuable contribution to the subject of
the electricity of flame has been lately
mtde by Ilerren Elster and Geitel. The dis-
crepancies in previous results are attributed

438

van nostband's engineeking magazine.

largely to the behavior of the air layer im-
mediately outside of the flame having been left
out of account. The authors used a Thomson
quadrant electrometer for measurement. They
find the supposed longitudinal polarization of
flame merely apparent, and due to unequal in-
sertion of the wires used as electrodes. On the
other hand, flame is strongly polarized in cross
section: an electrode in the air about the flame
is always positive to one in the flame . The
theory the authors adopt is this : By the process
of combustion per se free electricity is not pro-
duced in the flame; but the flame-gases and the
air-envelope have the property of exciting, like
an electrolyte, metals or liquids in contact
with them. To this electrolytic excitation
is added a thermo-electric, due to the in-
candescent state of the electrodes. The
amount and nature of the electric excita-
tion is independent of the size of the flame, and
dependent on the nature, surfaces condition,
and glow of the electrodes, and on the nature,
Nature says, of the burning gases. It is re-
marked that flames may be combined in series
like galvanic elements, and so as to form a
" flame battery."

Alloy for Silvering Metals. — A method '
for silveiing, or, more properly, whiten-
ing metals, has been recently devised by M,
de Villiers. It is a modification of the tinning
process, an alloy being used instead of the pure
tin. This alloy consists of 80 parts tin, 18
parts lead, and 2 parts silver, or 90 parts tin, 9
parts lead, and 1 part silver. The tin is melted
first, and when the bath is of a brilliant white
the lead is added in grains, and the mixture
stirred with a stick of pinewood, the partially-
melted silver is added, and the mixture stirred
again. The fire is then increased for a little
while, until the surface of the bath assumes a
light yellow color, when it is thoroughly
stirred up and the alloy cast in bars. The
operation is then carried out in the following
manner: — The article, a knife-blade for ex-
ample, is dipped in a solution of hydrochloric
or sulphuric acid, rinsed with clean water,
dried and rubbed with a piece of soft leal her or
dry sponge, and finally exposed to a tempera-
ture of 70 deg. or 80 deg. Cent. — 158 deg. to
176 deg. Fah. — for five minutes in a muffle, to
prepare the iron or steel to receive the alloy, by
making the surface porous If the iron is not
very good the holes are large, and frequently
flaws and bad places are disclosed, which
make the silvering more difficult. With steel
the process goes on very regularly. 1 he
article, waimed to say, 140 deg. Fah., is dipped
in the bath, melted in a crucible over a gentle
fire. The bath must be perfectly fluid, and is
stirred with a stick of pine or poplar; the sur-
face of ihe bath must have a fine white silver
color. For a knife-blade an immersion of
one or two minutes is sufficient to cover it;
larger articles require five minutes ot immer-
sion. After taking it out of the bath it is
dipped in cold water, or treated so as to temper
it, if necessary. If left too long in cold waier
it frequently becomes brittle. It is then only
necessary to rub it cff dry and polish witbout
heating it. Articles treated in tins manner

look like silver, and ring like it too, and with-
stand the oxidizing action of the air. To
protect them from the effect of acid liquids
like vinegar, they are dipped in a bath of
amalgam, composed of 60 parts mercury, 39
parts of tin, and 1 part of silver; then dipped
warm into melted silver, or electro-plated with
silver to give them the silvery look. This kind
of silvering is said to be very durable, and the
cost comparatively small.

MMekarski, well known in connection
# with compressed air tramway engines,
has published calculations to show that com-
pressed air could not be used for long tunnels
except at some difficulty. With a pressure of
5 kilogrammes per square millimeter, and an
average temperature of 15 deg. C, the work
of the compressed air, expanding two and a
half times, would be 11,179 kilogrammeters,
and the comsumption of air per hour per
horse-power would be 24 15 kilogrammes.
For one passage through the .tunnel, the con-
sumption of air at ordinary pressure woul cV
be 64,915 kilogrammes, or 177 cubic centim_
eters, at a pressure of 30 atmospheres. Plac-
ing the latter figure at 200 for safety's sake,
and computing the weight of the reservoirs to
carry the compressed air at 600 to 700 kilo-
grammes per cubic meter, we should have a
total weight of the tender containing the nec-
essary compressed air of 200 tons, which
would reduce the load carried from 400 tons,
as supposed in his calculations, to 200 tons.
M. Mekarski proposes instead, to use the or-
dinary locomotives, and to run them with a
mixture of air and steam. He carries the air
in reservoirs — capacity 20 cubic meters— at a
pressure of 35 kilogrammes per square inch.
These reservoirs communicate with theb<>iler
through an automatic device, which allows
the air to enter it only when steam pressure
falls below a given minimum. An auxiliary
pipe from the air reservoir is to be conducted
under the grate, in order to increase the rate
of combustion if necessary. The engineer
runs the locomotive with a growing quantity
of air as he gels farther into ihe tunnel, and
thusM. Mekarski thinks he could reduce the
quantity of coal burnt in the tunnel.

~r n a recent lecture on some of the dangerous
J properties of dusts, Professor Abel, F.R.S.,
said that many experiments were tried with
sensitive coal-dust from Seaham and other col-
lieries for the purpose of ascertaining whether
results could be obtained supporting the view
ihat coal-dust, in the complete absence of fire-
damp, is susceptible of originating expldsions
and of carrying them on indefinitely, as sug-
gested by some observers, but, although de-
cided evidence was obtained that coal dust,
when thickly suspended in the air, will be in-
flamed in the immediate vicinity of a large
body of flame projected into it, and will some-
times carry on the flame to some small extent,
no experimental results furnished by these ex-
periments warranted the conclusion that a coal
mine explosion could be originated and canied
on to any considerable distance in the com-
plete absence of fire-damp. Some experiments
made in a large military gallery at Chatham

MISCELLANEOUS.

431)

showed that the flame of a blown-out shot oi

1-) lbs. or 2 lbs. of powder might extend to a

maximum distance of 90 ft., while in ■ very
narrow gallery, similar to a drift-way in a
mine, the flame from corresponding charges

extended to a maximum distance of :5."> ft.
These distances arc considerably inferior to
those which flame from blown-out shots baa
been known to extend, with destructive re-
sults, in coal mines, and there appears do doubt
that, in the latter cases, of which the lecturer

e exam pits, the flame was enlarged and
prolonged by the dust raised by the concussion
of the explosion. Hut in the presence of only
very small quantities of fire-damp, dust may

iblish and propagate violent explosions; and
that, iu the case of a tire damp explosion, the
dust not ouly, in most instauces, greatly aggra-
vates the burning action and increases the
quantity of after-damp, but that it may
also, by being raised and swept along by the
blast of an explosion, carry the fire into work-
ings where no fire-damp exists, and thus add
considerably to the magnitude of the disaster.

Dr. Bjerknes has advanced beyond the
results of his experiments shown at
Paris. These were chiefly confined to illustrat-
ing the static attractions and repulsions of
electricity and magnetism, but he has now
taken up the subject of electro-dynamic attrac-
tions and repulsions. The former effects are
shown by brass balls oscillating, or by small
drums pulsating near each other in water.
These motions are communicated to the balls
and drums by pulses of air transmitted from
an ingenious air-pump or bellows along india-
rubber tubes. A pulsating drum corresponds
to a magnetic pole ; an oscillating body to a
magnet. When two drums are vibrating near
each other in like phase, they attract ; when in
unlike phase, they repel each other. The
same holds true of the oscillating balls. The
motion-lines round these bodies correspond to
the lines of force round magnets, as was de-
monstrated by a hollow ball oscillating on a
stem, and tracing its movements in ink on a
glass plate. The more novel part of the ex-
periment, Nature says, consisted in represent-
ing the attraction between two electric currents
flowing in the same direction by means of two
cylinders about 0 inches long and 1 inch in
diameter, oscillating round their longitudinal
axes at close quarters in the water. The cylin-
ders were oscillated 1)3" means of a pulsating
drum which communicated its motion to
them by a toothed gearing on their ends. At-
traction resulted when the oscillations of the
cylinders were opposed to each other, aud re-
pulsion when they were in the same direction.
A square of four oscillating cylinders was also
formed, and a fifth cylinder oscillated inside
it, the attraction or repulsion exerted on the
latter being observed. A hydrodynamic gal-
vanometer was made by placing an oscillating
ball beside an oscillating cylinder, the result
being a deflection of the ball according to the
direction of the oscillation of the cylinder.

The utilization of the earth's international
heat is a subject which, Nature says, is
attracting the attention of scientific men in

Japan just now. At a recent meeting of the
BeismoiOgical Society, Mr. Milne introduced
the subject for the consideration of the mem-
bers, lie first drew attention to the fact that
philosophers have told us ihe whole available
energy upon the surface of the earth had in
some way or other its action and its existence
traceable to the sun. That there was an un-
limited supply of energy in the interior of the
earth was a Circumstance which had, he said,

been overlooked. In Bpeakingof this energy,

Mr. Milne first referred to that, portion of it
which crops out upon the surface in countries
like Japan, Iceland and New Zealand, in tin'
form of hot springs solfataras, volcanoes, &c.
He stated that there was an unlimited supply
of water in hot springs within a radius of 100
miles arouud Tokio, and that the heat of these
springs could be converted into an electric cur-
rent, and the energy transmitted to the town.
The second part of the paper referred to the
possibility of obtaining access to the heat
which did not crop out in the surface.

rpHK pigments employed to color hydraulic
1 and other c meuts, and obtain the shades
common in trade, are, according to the Bauzeit-
ung, the following, the proportions used being
those used by R. Dyckerhoff, of xlmoeneburg :
For black, pyrolusite, 12 per cent. ; £or red,
caput mortuum, 6 per cent. ; for green, ultra-
marine green, 6 per cent. ; for blue, ultramarine
blue, 5 per cent. ; for yellow and brown ochre,
6 per cent. The strength of the cement is
rather increased by the addition of ultramarine
pigments, but somewhat diminished by the
others. The ill effects of the latter may be
somewhat removed by grinding the cement
again after the pigment has been added, where-
by it gains in fineness, and the strength is so
much increased that no difference is observable
between this and the ordinary cement. The
black and red cements made in Dyckerhoff's
works for making tiles and artificial stone
show a'strength by normal tests after twenty-
four hours' drying of 20 kilos, per square cen-
timeter, or about 275 lbs. per square inch — a
very respectable strain for such work. — Engi-
neer.

rpHE Magnaghi Floating Compass. — The
1_ floating compass, invented by Captain
Magnaghi, is now in use on board the Duilio,
and will probably be generally adopted in the
Italian Navy. Its main feature is the suspen-
sion of the needle iu water, to which has been
added one-tenth its volume of alcohol, con-
tained in a vessel with a perforated bottom,
which allows the liquid to rest ultimately on an
elastic diaphragm. The addition of the alco-
hol prevents the water from freezing under
low temperatures; and the elastic diaphragm
allows it to expand and contract during atmos-
pheric changes, without danger of breaking the
glass which covers it, or admitting air. On
this liquid the needle floats, enclosed in a
heremetically-sealed ellipsoidal case, which is
very delicately suspended npon a conical brass
pivot. The pivot has a sapphire top aud a jade
point, and the friction is diminished to the ut-
most possible degree by the most perfect polish.
The needle usually consists of six bundles,

440

VAN NOSTRAND'S ENGINEERING MAGAZINE.

each made up of five pieces of the best ribbon
steel, thoroughly tempered before being mag-
netized, and separately tested after. These
pieces are kept apart by strips of cardboard
soaked in oil, and their number can be in-
creased if necessary. Wherever in the appara-
tus two metal surfaces or edges meet, friction
is prevented, and closure secured, by a layer of
blotting paper soaked in mineral wax. This is
exclusively used for the purpose, because it is
insoluble in alcohol ; and even the marks and
figures in the outside ring are rendered distinct
by being filled in with the same substance
blackened. All the interior parts of the in-
strument are silvered, in order to prevent oxi-
dization and galvanic action between the va-
rious metals composing it, and to keep the
fluid perfectly colorless and transparent. The
compass proper (including the floating case
with the needles) weighs in the air about 750
grammes; but in the liquid it exercises a press-
ure of only about 6 grammes on the point of
support. The chief advantage claimed for this
invention is that the resistance of water being
great towards rapid movements and incon-
siderable towards slight ones, it leaves the
motions of the needle practically free, while
shielding it (by its own incompressibility) from
all shocks from without. The compasses of
the Duilio were not in the least agitated by the
discharge of the 100-ton gun, nor by the motion
of the screw, although the supports on which
they were placed were in such a position as to
feel the vibration greatly. 1 hey were some-
what disturbed by the rolling and pitching of
the vessel; and to meet this difficulty, modifi-
cations were made in the shape and arrange-
ment of the different paits, so as to render the
floating case thoroughly centrifugal, distribute
great portion of the weight round the circum-
ference, and fix the point of suspension very
little above the center of gravity. The result
of these arrangements is, that when the com-
pass is tilted by the movement of the ship, the
needle is so slow to change its position, that
before it has again become horizontal the
motion is reversed, and the inclination counter-
acted. The needle is also very little affected
by changes in the angle at which the terrestrial
magnetic current is inclined to the horizon,
which varies in different localities, in conse
quence of the needles being so much shorter
than the diameter of the compass, and being
placed too low with regard to the point of
suspension. This is proved by the simple test
of holding a powerful magnet directly over the
north point of the compass, when even this
great increase to the vertical force produces
only a very slight change in the inclination of
the needle. The compass is fitted with a
special sextant, in which various improvements
have been introduced, to increase the facility
and accuracy with which observations can be
taken, especially in twilight and cloudy
weather. A detaded description of both instru-
ments, with illustrations, will be found in the
Rivista Marittima for February and April.

A soft alloy which will adhere so firmly to
metallic, glass, and porcelain surfaces
that it can be used as a solder, and which is

invaluable when the articles to be soldered are
uf such a nature that they cannot bear a high
degree of temperature, consists of finely pul-
verized copper or copper dust, and is obtained
by resolving coppei sulphate, or vitriol of
copper, into its original elements, by means of
metallic zinc. Twenty, thirty, or thirty-six
parts of this copper dust, according to the
hardness desired, are placed in a, cast iron or
porcelain-lined mortar, and well mixed with
some sulphuric acid having a specific gravity
of 1.85 Add to the paste thus formed 70 parts
(by weight) of mercury, constantly stirring.
When thoroughly mixed the amalgam must be
carefully rinsed in warm water to remove the
acid, and then laid aside to cool. In ten or
twelve hours it will be hard enough to scratch
tin. When it is to be used it should be heated
to a temperature of 375 degrees C. ; when it be-
comes as soft as wax by kneading it in an iron
mortar. In this ductile state, the Scientific
American says, it can be spread upon any sur-
face, to which, as it cools and hardens, it ad-
heres very tenaciously.

It is stated that a new lamp combining gas
and electricity, giving remarkably econom-
ical results, has been brought out. It will be
remembered that some years ago gas burners
were not uncommon which had a small piece
of platinum foil arranged on the burner so as
to be burned in the flame. When this was
heated by a gas flame, it, by a regenerative ac-
tion, heated the gas coming from the burner,
and caused an improvement in the light. The
new lamp is essentially, it is stated, this burner
arranged so that a small current of electricity
is passed through the platinum. The gas is
first lighted, and this heats the platinum, the
resistance of which is thus increased, so that a
current which would when the platinum is
cold, be freely transmitted, now heats the plati-
num to incandescence, and thus in turn heats
the issuing gas to a very high termperature, so
that a light equal to 30 candles is, it is said, ob-
tained by the consumption of 2 cubic feet of
gas per hour, and a small electric current. If
this is the case, the existing gas fittings are all
utilizable, and a secondary battery of no great
number of elements, and charged with a cur-
rent of about 2^ volts E.M.F., would supply
the current needed.

TT^unnel Ventilation. — A "chemical lung"
_1_ is the latest thing proposed for the venti-
lation of tunnels. It w as lately tested in London
by fourteen scientists. A room 15' x 18' was
kept for an hour at a temperature 0/ 82.
degrees, and the air was loaded with impuri-
ties. The men of science were now called
upon to enter, and the air was made still
more impure by burning sulphur and carbonic
acid gas. Then the "chemical lung," or
punkah, so called, measuring 4'x 2' 6", was
set in motion. The temperature was soon
reduced to 65 degrees, and the air freed from
all impurities. Then fat was burned,, to test the
machine for organic substances, and the "lung"
was started up just in time to prevent the
examining gentlemen from running out for fresh
air. It is proposed to use the invention during
the construction of the channel tunnel-

VAN NOSTEAND'S

Engineering Magazine

NO. CLXVIII.-DECEMBER, 1882.-V0L. XXVII.

THE THEORY OF THE GAS ENGINE.

By DUGALD CLERK.

From Proceedings of the Institution of Civil Engineers.

II.

DISCUSSION.

Mr. D. Clerk mentioned that Dr. Sie-
mens had worked out the nethod of
compression used in engine type 2 in
1860 in so complete a manner that no
advance had since been made on it by
any one. Dr. Siemens was again work-
ing at this type of engine, which, from
the fact of it using hot cylinder and re-
generator, Mr. Clerk was certain was the
best type for the very large gas engines
to be developed in the future. With re-
spect to the cold cylinder engine, of which
alone he had treated in the paper, he
wished again to insist on this : that the
theory which sought to explain the so-
called sustained pressure on the
indicated diagram by the hypothe-
sis of slow inflammation (erron-
eously termed slow combustion) was a
false one. That when maximum pressure
was attained in the gas engine cylinder
it was certain that the whole mass was
completely inflamed, and that no system
of stratification producing slow inflam
mation could do good, but was quite
opposed to the conditions of economy.

Dr. Siemens said that one part of the
paper dealt with matters regarding the
mechanical arrangement of gas engines,
Vol. XXV1L— No. 6—31.

and the other with a theoretical question,
that of the law of combustion. He would
refer to the theoretical part first, because
the author appeared to attach great im-
portance to it. and as Dr. Siemens had
from time to time given a great amount
of consideration to the action of negative
combustion or dissociation, it might be
of some interest to the members to see
how far his views fell in with those set
forth by the author. It was well known
that by combustion no unlimited degree
of temperature could be attained. Thus,
in a furnace worked at very high temper-
ature the fuel was not completely burned
when it came in contact with the oxygen
of the heated or non heated air. The
moment a certain comparatively high
temperature was reached the carbon re-
fused to take up oxygen, or the hydrogen
refused to take oxygen, and what had
been called by Bunsen, and, shortly after
him, by St. Claire Deville, dissociation,
arose. The point of dissociation was not
a fixed one ; partial dissociation came in-
to play at a comparatively low tempera-
ture, and went on increasing at a higher
temperature in very much the same ratio
as vapor density increased with temper-
ature. Thus, if aqueous vapor were
passed through a tube at a sufficient

442

van nostrand's engineering magazine.

temperature the whole of the vapor
would be dissociated, and the oxygen
and the hydrogen would be separated.
It was true, if these gases were left to
themselves they would, the moment the
temperature lowered again associate or
burn ; but if precautions were taken to
cool them rapidly after they had attained
that high temperature they would be
found as a mixture of oxygen and hydro-
gen simply. The author had stated that
the law which governed these actions was
not well known and required research,
but Dr. Siemens would like to know
whether he was aware of the researches
of St. Claire Deville on the subject. It
might be that the determinations of St.
Claire Deville were not quite correct, but
in the meantime they might be regarded
as being so. He found that at atmos-
pheric pressure the point of half dissocia
tion of aqueous vapor arose at a temper-
ature of 2,800° Centigrade, and that of
complete dissociation at a much higher
temperature. Taking that law as deter-
mined by the French philosopher, it did
seem reasonable to suppose that when a
mixture of hydrogen and oxygen, with or
without a mixture of nitrogen exploded,
the point was reached beyond which the
temperature did not increase, and, accord-
ing to the author, that point was 1,500°
Centigrade. If such a temperature was
reached in a working cylinder complete
combustion would not take place imme-
diately, but only partial combustion
would occur, which would go on as the
temperature diminished by absorption
into the cylinder or by expansion, and
that combustion would be completed
only in the course of the stroke. In that
way the action which had been described
with reference to the diagrams was rea-
sonable enough. With regard to the
mechanical arrangement of gas engines,
the author distinguished between three
types. In the first, the mixture of gas
and air drawn in at atmospheric pressure
was exploded. In the second, with which
the author had connected his name as
that of the first proposer, the combustion
was produced gradually ; the gases were
ignited as they flowed into the heating
cylinder. In the third type, the gases,
after being compressed and mixed, were
admitted into the working cylinder, and
suddenly exploded. "With reference to
the early engine which Dr. Siemens con-

structed in 1860, the author had stated
that it combined other elements, which
were entirely wanting in the gas engines
of the present day. The gas engine of
the present day, taking either of the three
types, was, in his opinion, in the condi-
tion of the steam engine at the time of
Newcomen. The fuel was burnt in a
cylinder which it was attempted to keep
cold by passing water over it, and it was
easy to conceive that the heat so generat-
ed, was only partly utilized for maintain-
ing the state of expansion of the heated
gases, the cold sides of the cylinder tak-
ing a good half of it away at once, thus
causing a great loss. Then there was
another palpable loss in these engines.
After expansion had taken place, after
half the heat had been wasted in heating
a cylinder which was intended to be kept
cool in order to allow the piston to move,
the gases were discharged at a tempera-
ture of 1,000°, or in the best types about
700°. That amount of heat, representing
in one case one-half and in the other
two -thirds of the total heat generated,
was thrown away. This was heat which
could be saved and made useful. Instead
of commencing the combustion at a tem-
perature of 60°, if the heat of the outgo-
ing gases were transferred to the incom-
ing gases, combustion, might commence
at a temperature of nearly 1,000°, and the
result would be a very great economy. In
the engine which he constructed in 1860
(Fig. 13) all those points were fully taken
into account. The combustion of the
gases took place in a cylinder without
working a piston, and in a cylinder that
could be maintained hot, and the gases
after having completed expansive action,
communicated their heat by means of a
regenerator to the incoming gases before
explosion took place. Although the en-
gine was not worked with ordinary- gas
used for illumination, but by a cheaper
kind made in a gas producer, he.then
thought that a gas engine constructed
on that principle would prove to be the
nearest approach to the theoretical limits
which could never be exceeded, but which
might exceed the limits of the steam en-
gine four or five fold. The engine prom-
ised to give very good results, but
about the same time he began to give his
attention to the production of intense
heat in furnaces, and having to make his
choice between the two subjects, he se-

THE THKoky OF ill i: G \s EN GIN E.

448

1 the Furnace and the metallurgic
process leading out of it ; and that was
why the engine had remained where it
was for so long a time. Bui now the
time had come when there was a greater

demand for engines of a smaller kind to
do their best in houses and in small
works, and when marine engineers espec-
ially had become fully alive to the im-
portance of more economical arrange-
ments. He therefore looked upon the
question before the Institution as one of
first importance to engineers, and he
hoped that it would be well discussed.

Professor Ruckrb said that, iii bis work
on Thermodynamics, Mr. Verdet had
published a calculation of the theoretical
efficiency of an ideal gas engine. He as-
sumed that no heat was lost through the

sides of the cylinder, and thai the explo-
sion was so sudden thai the whole of the
I gas was inflamed before the piston had
appreciably moved : and under those cir-
cumstances he found that if the gaSCS
used were carbonic oxide, and a sufficient
quantity of air to bum it completely, and
if the whole of the carbonic oxide was
burnt, the temperature to which the gases
would rise, on the assumption that their
specific heats remained constant, was
4.888° Centigrade. He found that the
pressure would rise from 15 11 >s. per
square inch to 215 lbs., and that the effi-
ciency of the engine would be 41 per
cent. — that was, that 41 per cent of the
total amount of heat produced by com-
bustion of the gas would be converted
into useful work. It was evident from
the conditions of Mr. Yerdet's problem
that that was a purely theoretical calcu-
lation. The condition, for instance, that
no heat was lost was one which could
not be realized in practice. About four
years ago, however, in the course of a
series of lectures given by some of his
colleagues and himself on coal, he pointed
out that Mr. Verdet's calculation was not
even theoretically correct; that Bunsen
had proved that it was impossible that a
mixture of carbonic oxide and air could
reach such a temperature as 4,388° Cen-
tigrade, which was something like 2,800°
above the highest temperature, which
Berthelot had shown was consistent with
Bunsen's experiments on the subject.
The question then arose what the effect
of dissociation would be upon the gas
engine, and Professor Rucker attempted
to make a rough calculation to show how
important it might be. In the first place,
he assumed that the highest temperature
which could be reached was that given
by Bunsen's experiments, and in the next
that the specific heats were constant and
the inflammation instantaneous. With
those conditions only about one-half of
the carbonic oxide would be burned
when the highest temperature was
reached; then, as the piston began to
move forward and the temperature fell,
more would be consumed. But then
there was the very important question

444

VAN NOSTRAND'S ENGINEERING MAGAZINE.

as to how the temperature would
fall, and in order to calculate that
the law of cooling of a body heated to
that extremely elevated point must be
known. That, of course, he was igno-
rant of, and he was therefore obliged to
make a rough assumption. Assuming
that, as the piston moved forward, the
gas burned so as to keep the temperature
constant, he found that at the end of the
stroke, when the pressure had fallen to
that of the atmosphere, a part of the gas
was left still unconsumed. Therefore
in the half of the gas left un burned to
begin with, there was sufficient to do all
work that was done while the piston
was moving forward. The only assump-
tion he could make was that the tem-
perature remained constant ; any other,
though that certainly was not true,
would have involved some still more
arbitrary hypothesis as to the law of
cooling. Making, then, that rough as-
sumption, he found that instead of a
temperature of 4,000° Centigrade the
highest reached would be about 2.0>i0°;
that the pressure, instead of rising to
215 lbs., would rise only to 103 lbs.;
and that the efficiency of the engine
would be only 25 instead of 41 per cent.
That, though a very rough calculation,
showed at once what the enormous im-
portance of the phenomenon of disso
ciation might be. It served the purpose
for which it was put forward, and
showed that in any theory of the gas
engine physicists must make up their
minds as to what part dissociation
played in it. Passing from the theo-
retical problem to that Mr. Verdet and
himself discussed, name y, the case in
which there was only enough air to
burn the carbonic oxide completely, to
the practical problem in which there
was a much larger quantity of air pres-
ent, a case arose in which dissociation
was less important. The larger the
quantity of air present the lower the
highest temperature would be, and
therefore, probably, the smaller the
amount of dissociation. St. Claire De-
ville had shown that carbonic acid was
dissociated at temperatures between
1,000° and 1,200°, and water at temper-
atures between 1,000° and 1.10vJ° Centi-
grade. Inasmuch, therefore, as in the
author's engines, the highest temperature
reached was about 1,500° (or 400° or

500° above the limits put by St. Claire
Deville), it followed that if his measure-
ment of the temperature was correct,
which there was every reason to believe
it was, and if St. Claire Deville's experi-
ments were trustworthy, there was a
certain amount of dissociation at the
temperatures reached in his gas engine.
Passing, however, to the next question,
namely, how much dissociation there
was, the problem was much more diffi-
cult. With regard to that subject a
series of papers had recently appeared in
the " Comptes Rendus de l'Academiedes
Science," which were so much to the
point that he might be excused for giving
a short account of one or two of the lead-
ing results at which the experimenters
had arrived. The two gentlemen in
question were Mr. Mallard (whose ex-
periments on the rate of propagation of
inflammation in gas had been mentioned
by the author) and a colleague, Mr. Le
Chatelier. They had been making a
number of experiments such as those
that the author had advocated in his
pnper. They had made, indeed, what
appeared to be one of the first serious
attempts to investigate what was going
on in gas heated between 1,000° and
1,500° Centigrade. The plan they adopt-
ed was as follows : They exploded gases
in an iron cylinder, attached to which
was a Bourdon manometer; to that was
attached a needle, which registered the
pressure on a revolving cylinder. By
reading off the curve so obtained, they
got information as to the pressure in the
cylinder at different times. He could
not altogether accept their results with-
out further confirmation. Some of the
conclusions at which they had arrived
were so striking that he thought they
must certainly be supplemented by other
experiments before they could be accept-
ed. But for the moment he would put
aside all difficulties connected with", the
experiments, and simply state the con-
clusions. It was found, dealing with.
gases at very different temperatures, that
the curves obtained upon the revolving
cylinder showed a point of discontinuity.
At the very highest temperatures- the
curves were somewhat different from
what they were at low temperatures, and
the assumption they made was that at
the high temperatures dissociation had
set in, whereas at the lower temperatures

THE TIIKOKY OF THE GAS ENGINE.

n:»

there was no dissociation; therefore the
law of cooling would be different in the
two eases. If, however, that interpreta-
tion of the experiments was accepted, it
would be found that the temperatures at
which dissociation took place to any con-
siderable extent were higher than those he
had mentioned. Thus the authors stated
that carbonic acid did not dissociate ap-
preciably below 1,800 Centigrade, and
that steam-gas did not dissociate appre-
ciably below 2.000°. Here, then, there
were temperatures considerably above
those obtained in the gas engine ; if,
therefore, the results in question were to
be accepted, dissociation could not play
a very important part in the matter. But
although at first sight the experiments
told against dissociation taking place to
any large extent, in order to account for
the phenomena they observed, Messrs.
Mallard and Le Chatelier had had to in-
troduce another hypothesis which practi-
cally came to very much the same thing.
In all the earlier calculations upon the
subject the assumption had been made
that the specific heats of the gases were
the same at high as at very low temper-
atures, but within the last few years two
or three experimentalists of note had
brought forward results tending to showr
that the specific heat of the gases in
creased as the temperature rose. The
two most important researches made
upon the subject wrere those by Profes-
sor E. Wiedemann and Professor Wii li-
ner, the latter of whom showed that at
temperatures between zero and 100°
Centigrade there was an appreciable rise
in the specific heat of gases at a constant
volume. Messrs. Mallard and Le Cha-
telier had taken that hint, and they found
that in order to explain the facts ob-
served by them on the assumption that
there was no dissociation, they must as-
sume an enormous increase in the speci-
fic heats of the gases at high tempera-
tures. But there were one or two points
which appeared to present difficulties in
their way. Wullner showed that at the
temperatures at which he worked, as
might be prima facie expected, the in-
crease was much greater in a compound
gas like water or carbonic acid than in
an elementary gas such as oxygen or ni-
trogen. But Messrs. Mallard and Le
Chatelier completely reversed that, and
found that the increase was much greater

in the elementary gases than is the com-
pound ones; and they weld so far as to
show that oxygen would at a tempera-
ture of l.ooo have a specific heat do

less than one hundred and sixty five
times greater than that which it. had at
Zero. That result was so astonishing
that it could not be accepted without
much more proof than had at present
been ottered. But putting aside for the
moment Messrs. Mallard and Le Cha-
telier's interpretation of the experiments,
he wished to consider what they meant
from a wider point of view, viz , that
those gentlemen had come across a
phenomenon which pointed to the fact
that a vast quantity of heat was ren-
dered latent. If specific heat at constant
volume increased, the meaning of it must
be that the work done by the heat was
done within the molecules of the gas,
that the heat was spent in separating
or preparing for separation the atoms
of those molecules, which were gradu-
ally being forced asunder ; whether they
were actually forced asunder or not
might be a question, but a large amount
of work was spent in separating them, or
preparing to separate them, by loosening
the bonds between them ; and Messrs.
Mallard and Le Chatelier's experiments
served as much as anything previously
brought forward to illustrate that point.
He thought it must be assumed with al-
most certainty that a large quantity of
heat was rendered latent in gases at
temperatures between 1,000° and 1,500°
Centigrade. All would agree that a cer-
tain amount of that heat was spent in
dissociation (for Messrs. Mallard and Le
Chatelier stated that they harmonized
their results with those of St. Claire De-
viile by supposing that his experiments
were more sensitive than their own), and
the remainder of the heat would be
spent, if not actually in dissociation, in
preparing for dissociation. There was
one other point in the paper which he
thought of interest. The author had
pointed out how different the rate of
propagation of an explosion would be in
the case of gaseous mixture which was
confined to that in an unenclosed space.
Messrs. Mallard and Le Chatelier had
made experiments on that point ; they
had inflamed gas and air mixture in a
tube closed at one end, and they found
that when it was inflamed at the closed

446

van nostkand's engineering magazine.

end the rate of propagation was much
greater than when it was inflamed at the
open end. In the one case the gas was
merely burning backwards through the
tube, in the other the expansion of the
gases would spread the inflammation.
So enormous was the difference, that in
some cases they found that the rate of
propagation was one hundred times
greater when the gas was lighted at the
closed end of the tube than when it was
lighted at the open end. That was a
point which strongly confirmed the au
thor's view — that inflammation spread
through the gas almost instantaneously.
Although, therefore, one could not but
feel that on those points there was a
great lack of experimental data, all the
facts that were brought together, might,
at present, be best explained by the hy-
pothesis that the inflammation spread
very rapidly through the gas, and that
at high temperatures, say of over 1,000°,
a very large amount of heat was rendered
latent, either in actual dissociation or in
incipient dissociation. Here, then, was
an explanation of the curious maintain-
ing of the temperature to which the au-
thor had referred. As the gas cooled,
the latent heat was given up and the
curve was thus kept up to a high tem-
perature by the heat previously absorbed
in the molecules of the gas.

Mr. W. E,. Bousfield did not propose
to quarrel with the greater part of the
facts stated, which were for the most
part indisputable, but he thought neither
the interpretation which the author had
put upon them could be upheld, nor the
new and) to most of them, rather start-
ling theory of the action of the gas en-
gine which had been submitted in the
paper. He did not say that the phenom-
ena of dissociation played no part in
the action of the gas engine ; he did not
say that when the explosion took place,
there might not be a certain quantity of
ammonia and a certain quantity of nitric
acid formed, and that the phenomena of
dissociation might not take place to a
certain extent ; but what he did say was
that neither the formation of nitric acid
nor the formation of ammonia nor any
of the phenomena connected with dis-
sociation could account for the facts
mentioned. He would only refer to two
of those facts, namely, that notwithstand-
ing the enormous loss of heat through

the walls of the cylinder of a gas engine,
amounting to 50 per cent, of the total
amount of heat put into the cylinder, the
curve of the indicator diagram still kept
up the theoretical adiabatic line which it
should follow, supposing the whole of
the gas were burned at the beginning of
the stroke, and the walls of the cylinder
were non-conducting. That was a start-
ling fact which had to be dealt with in
one way or another, but the interpreta-
tion of the fact seemed to him to be very
simple, and even in the paper there were
materials for arriving at a conclusion
upon it. The author had stated that a
mixture of gas and air took a certain time
to ignite, that if ignition was set up at
one point it took a certain time before it
was communicated to another. There
was also the further fact that at the rate
of communication of the ignition from
one point of the dilute mixture to an-
other varied directly with the amount of
dilution of the mixture. Supposing for
instance there was a mixture of gas and
air in the right proportions for explosion,
the ignition would take place at a certain
speed ; if more air was put in, the rate
would be less ; the greater the quantity,
the less the rate at which the ignition
traveled. That simple fact he thought
sufficient to account for all the phenom-
ena. The diagram which the author
had given (Fig. 9) seemed to him, taken
in conjunction with the fact to which he
had referred, to support the theory
which had been put forward by Mr.
Otto and by the scientific world in gen-
eral. In the Otto gas engine the charge
varied from a charge which was an ex-
plosive mixture at the point of ignition
to a charge which was merely an inert
fluid near the piston. When ignition
took place, there was an explosion close
to the point of ignition that was gradu-
ally communicated throughout the ^mass
of the cylinder. As the ignition' got
further away from the primary point of
ignition the rate of transmission became
slower, and if the engine were not
worked too fast the ignition should
gradually catch up the piston during its
travel, all the combustible gas being thus
consumed. When the engine was worked
properly the rate of ignition and the
speed of the engine ought to be so timed
that the whole of the gaseous contents
of the cylinder should have been burned

THE THEOEl OF THE G \- ENGIH E.

1 17

out and have done their work some little
time before the exhaust took plac<

that their full effect could be si-en in the
working oi the engine. This was the
theory of the Otto engine. What was
the theory which the author had put for-
ward? He had stated thai when gases
combined a high temperature was set
up: that a high temperature prevented
combination of the beyond a cer-

tain point; and therefore, at the moment
of ignition, then' existed in the cylinder
a body of gases heated to a temperature

nd the point of dissociation. Apart
of those gases being in a state of com-
bination, and having therefore given out
a heat which was doing the work of push-
ing the piston ; a part of the gases, not

4- in a state of combination, being
ready to combine as soon as the tempera-
ture was lowered to such a point that
they could combine and give out work.
Looking at that theory, it seemed as if
the point involved was a mere question of
words, so far as regarded any question
of infringement. In either case, what
had to be dealt with was this. The adi-
abatic line represented the line which

traced out upon the indicator dia-
gram when no heat escaped through the
walls of the cylinder, and when the whole
heat which the gases lost was converted
into work done by the piston ; so that,
taking an indicator diagram, and finding
the work done as represented by the
area included by the curve, the ordinates
and the atmospheric line, this work ought
to be equal to the quantity of heat, rep-
resented in foot-lbs., which had been
given out by the gas, as shown by the
difference of temperatures and specific
heat of the gas. Of course, when heat

escaping through the cylinder, and
when the adiabatic line was still kept up
to, a considerable amount of energy
must be developed somewhere, in order
to make up for the energy which went
through the walls of the cylinder. The
only source of energy in the gas engine
was the union of combustible gases and
oxygen, and it followed that that con-
stant supply of energy must come from
the combustion of the gases within the
cylinder. It was therefore a mere ques-
tion of words, because, whether the en-
ergy was developed by the combustion
of the gases which took place through
the lowering of the temperature below

the point, of dissociation, or whether
that energy was given out through the
combust ion of the gases which took
place from the communication through

the mass of an ignition which traveled

slowly through it, in either case it w;is

a gradual combustion. It was therefore
a mere question of theory, and he did

not see in what way it could affect the

question of infringement. If Mesers.
Crossley and Mr. Otto had overlooked

the theory of dissociation, and had at-
tributed the gradual combustion to
something which they ought not to have
attributed it to, he did not see how it
could affect their position. The real
point of difference, however, in a scien-
tific point of view, between the author
and himself was this. The author as-
sumed that the ignition was quickly
transmitted thiough the cylinder, and
i took place almost at once near the be-
I ginning of the stroke, and that the ulti-
mate combustion was due to dissocia-
tion ; whereas Mr. Bousfield thought
with Mr. Otto and many others that t he
cause of the supply of energy was the
gradual communication of ignition
through the contents of the cylinder.
The author assumed gratuitously that
when the point of maximum pressure
was reached, that point marked the
communication of ignition throughout
the whole of the cylinder. That there
was absolutely no ground for that as-
sumption could be very readily shown.
Neglecting for the moment the loss of
heat through the walls of the cylinder,
the curve representing the mere ise of
pressure due to the combustion of the
gas, supposing the gases to combine at
the same rate as they actually did, but
not to be allowed to expand by the mo-
tion of the piston, could be as ertained
thus : — Divide the atmospheric line (Fig.
14) into spaces AB, BC, CD, DE, etc.,
repre enting equal small spaces of time,
or equal parts of a revolution. From
each of the points A, B, C, &c, raise
ordinates AL, BF, CG, &&, to meet the
indicator curve in the points F, G, H,
&C, and from the points F, G, H, etc.,
draw adiabttics to meet AL in L, M,
N, etc. From L, M, N, etc., draw lines
parallel to AB to meet their correspond-
ing ordinates in P, Q, R, &c. Then the
curve P, Q, R, etc., drawn through these
points, would be a curve, the ordinates

448

van nostrand's engineering magazine.

of which were proportional to the press-
ure at any time of the contents of the
cylinder, supposing these contents to re-
main confined in the space at the end
of the cylinder, and not allowed to ex-
pand, and supposing the rate of com-
bustion of these contents to be exactly
the same as actually occurred. This
curve, therefore, showed the actual prog-
ress of the combustion deduced from

the stroke. Hence the maximum point
on the diagram was simply the point
where the increase of pressure due to
combustion was balanced by the decrease
of pressure due to the forward motion
of the piston, and there was no reason
for saying that this maximum point cor-
responded to complete ignition. He had
had an opportunity of taking diagrams
from the Otto gas engine, which Pro-

the working diagram. Even neglecting
the loss of heat through the walls of the
cylinder, it would be seen that this curve
ascended to a point past the point of
maximum pressure, viz., till the point
K, at the commencement of the part KV
(which was supj^osed to be exactly adi-
abatic) was reached. From the point S
this curve became in the actual diagram
a straight line parallel to AB. If, how-
ever, the theoretical diagram, allowing
for loss by conduction, were taken, the
curve PQRS would ascend throughout

fessor Ayrton had at the City Guilds
Technical School, Cowper Street. The
engine was designed for the electric
light, and the cam, controlled by the
governor, was made in a series of steps.
He therefore had the governor taken
off, and the cam and the roller on
which it acted so arranged that it should
work independently of the velocity of
the engine on a given step, so that the
charge might be, as nearly as possible,
the same at all speeds. And he varied
the load by braking the fly-wheel. The

ill I. THEORY OF Til E (*A8 i:\<;in E.

449

two Beta of diagrams were taken, one al
a Bpeed of one hundred revolutions, and
the other al two hundred; thus might
be seen the effect which must he due t<>
the phenomenon he had spoken of — the

nomena of dissociation, when they could
be perfectly explained by the rate
progress of ignition through the cylinder.
With the full charge at one hundred

and at two hundred revolutions the

4th step. 100 to 200 revolutions.

ignition traveling gradually; it could not
be due to dissociation, for the reason
which Mr. Imray had pointed out. In
the diagrams the phenomena of dissoci
ation ought to be exaggerated at the
higher temperature, but instead of that,

effect of difference of speed was small,
as shown by the two diagrams in Fig.
15. In that case, the rate at which the
ignition went through the cylinder was
so great that it only made a very little
difference in the curve when the rate got

3d step. 100

it would be seen that the effects at-
tributed to dissociation were less at the
higher temperature where dissociation
should be most active, and greatest ;it
temperature below the point of dissoci-
ation ; he therefore did not see why the
results should be attributed to the phe-

to 200 revolutions.

up to two hundred revolutions. He then
fixed the roller on the third step, when
there was a less charge of gas. The
diagram, Fig. 16, showed the hundr
revolution curve, in which the gas had
time to explode, and to carry the pencil
indicator up to the maximum point, and

450

VAN NOSTRAND'S ENGINEERING MAGAZINE.

then down to the adiabetic line. Going
to two hundred revolutions with the
more dilute mixture, the rate of propaga-
tion of ignition was slower ; therefore at
that speed, although the temperature
was less, dissociation would have much
more to do. The effect was much more

it to the author to show how he ex-
plained the diagrams under the dissoci-
ation theory. In Fig. 18 there was the
least amount of gas with which the en-
gine would work, and the speed was one
hundred and thirty revoluions. The
compression was 30 lbs. ; the compres-

2d step. 100 to 200 revolutions.

marked, simply from the dilution of the
mixture ; there was therefore a less rate
of propagation of ignition, and the curve
took the form shown in the diagram.
Fig. 17 showed the same effects on the
diagram when the curve roller was on
the second step, and consequently still
less gas was admitted. The five super-

sion line was the same as the others.
The working line was a line nearly par-
allel with the atmospheric line, but
slightly rising, and at the end the ig-
nition was not finished, indeed, in this
case, if a light was applied to the ex-
haust the contents would explode. Ac-
cording to the author's theory, that

Fig.18.

1st step. 130 revolutions.

posed diagrams were taken at speeds be-
tween one hundred and two hundred
revolutions per minute. It would be
observed that the curve at the higher
speed generally went Outside the door
There was less work done at the begin-
ning, and more gas to be combined at
the end, and therefore a greater amount
of work done at the end of the stroke.
He did not wish to carry the comparison
all the way through, but he would leave

maximum point near the end of the
stroke in the last diagram was a point
where the ignition was complete, and
therefore all the gas should have combined
at that low temperature where no dis-
sociation could take place. Those were
points which the author would have to
meet in order to support his theory.
Many cf the facts mentioned by the
author we e incontestable, and his chief
dispute with him was as to the interpre-

THE THEORT OF THE G \- ENGINE.

461

tatioo he had put upon them. The an
thor had said nothing against the theory
to whieh he had referred except that it
was new, do argument whatever being
advanced against it. The author Btated,

•-From the considerations advanced in
the course o\' this paper, it will be seen

that the cause of the comparative effi-
ciency of the modern typeof gas engines

over the old Lenoir and BugOD is to be
summed up in one word, ■ compression.'"
He had not had time to go carefully
through the diagrams; but he did not

think that they were fair comparisons,
and he thought that other elements

ought to have been taken into account.
The author had given the old Lenoir,
and had stated that the temperature was
the same, that the mixture of gas was
the same, and that the great advantage
over the Lenoir was compression. Mr.
Boustield might be permitted to point
out that, in the Lenoir engine, the adi-
abatic line was much above the actual
line. It would be fairer to substitute
the word " dilution " for " compression,"
so that the sentence would read: "The
cause of the comparative efficiency of
the modern type of gas engines over the
old Lenoir and Hugon is to be summed
in one word, ' dilution.' ': The fact, how-
ever, was that it could not be summed
up in one word ; the two should be taken
together, compression and dilution.
The author further stated : " The pro-
portion of gas to air is the same in the
modern gas engine as was formerly used
in the Lenoir." # He did not think so.
He believed that the Lenoir worked up
to 13 to 1, and could not get further.
He did not know what proportion Otto
used, but it was considerably more than
that. It was also stated that the time
taken to ignite the mixture was the same ;
but that was a gratuitous assumption.
The author said : " The cause of the sus-
tained pressure shown by the diagrams is
not slow inflammation (or slow combustion
as it has been called), but the dissociation
of the products of combustion, and their
gradual combination as the temperature
falls, and combination becomes possible.
This takes place in any gas engine, whether
using a dilute mixture or not, whether
using pressure before ignition or not,
and indeed it takes place to a greater ex-
tent in a strong explosive mixture than
in a weak one." Dissociation took place

far more at high temperatures than at
low; and if the author's application of

the theory were eorrecl the phenomena

of dissociation ought to play a much

greater pot at high than .-it low tem-

I ores. lie had pointed out that this
was not so in the diagrams, and that it
was not SO with Lenoir's explosive en-
gines where the CUTV6 fell far below the

adiabatic line. The paper contained
other matters which he had not tine to
dwell upoh; but he thought he had said
enough to challenge the author to show
how he got rid of the old theory, and ex-
plained the facts to which Mr. Boustield
had referred.

Dr. John Hopkinson said a very inter-
esting question had been discussed by
Professor Riicker and Mr. Boustield, to
which he desired to refer. The author
maintained that the ignition of the mix-
ture of gases had extended throughout
the whole space at a time approximately
represented by the point of maximum
pressure. Others, on the contrary,
maintained that the ignition had not ex-
tended through that space by that time,
but that it took a time lasting into the
descending part of the indicator diagram
before the disturbance had extended
throughout the whole of that space.
The author attributed the maintenance
of the temperature during the latter
part of the curve, and its approximation
to an adiabatic curve, to the gradual
combination of the gas through the mass,
that combination not occurring com-
pletely in the first instance owing to the
temperature being so high that a certain
measure of dissociation occurred, or at
all events so high that comptete com-
bination could not occur. He thought
that the question might be submitted to
a crucial test. Suppose the opponents
of the author were right, if a given mix-
ture#of air and gases were exploded in a
gas engine revolving at a low rate of
i or in an entirely closed space, it
would be expected that the maximum
pressure would approximate to that
calculated from the heat due to the com-
bustion of the gas present and the tem-
perature resulting therefrom. If the
gine were running slowly, or if \\\'.' ex-
plosion were made in a completely
confined space, the pressure would be
expected to rise to a point very greatly
in excess of that observed in the gas

452

VAN NOSTRAND S ENGINEERING MAGAZINE.

engine running at its normal speed.
Whether that were so he did not know.
The experiment might be objected to on
the ground that when the engine was
running slowly there was a great loss of
heat through the walls of the cylinder.
That would give rise to a second crucial
experiment. If the author was right the
maximum pressure in large and small en-
gines would be about the same ; if those
who differed from him were right, in a
large engine the maximum pressure would
probably be greatly in excess of that in
a small engine, there being less loss of
heat through the walls of the cylinder.
What the answer might be he did not know,
but it appeared to him that there were
there the elements of settling the ques-
tion. The author divided gas engines
into three classes, and had made a com-
parison of their theoretical efficiency.
In the second the mixtures were ad-
mitted into the cylinder, and, without
increase of pressure, the heat produced
was devoted to increase of volume. In
the third the mixtures were introduced
into the cylinder, and then burned with
an increase of pressure without immedi-
ate increase of volume ; and in those two
cases he took, for the purpose of com
parison, different maximum pressures.
In the second type he took a pressure
•of 76 lbs., and in the third over 200 lbs.
Prima facie it would seem natural, in
order to make a fair comparison, that the
same maximum pressure should be taken
in the two cases. Probably the author
had a good reason to justify his making
a comparison on that basis, and, per-
haps, in his reply he would point it out.
He agreed with those who had so often
spoken on the subject of the gas engine
that in that engine lay the future of the
production of power from heat of com-
bustion. It was quite in its infancy, and
it had already beaten the best steam en-
gines in economy of fuel, for the obvious
reason that it was practic ible to use
with it much higher temperatures. The
steam engine tolerably approximated to
the theoretical efficiency that might be
expected from it, having regard to the
temperatures between which it was prac-
ticable to work it. That was not the case
with the gas engine, there being still a
very large margin for practical improve-
ment. Having regard to the very short
time during which gas engines had been

used, he thought that practical improve-
ments would take place, and that, when
such difficulties as that of starting a
large engine as conveniently as steam en-
gines could be started had been over-
come, the gas engine would supersede
the steam engine.

Mr. E. F. B amber wished the author
had commenced his paper with that por-
tion which treated of the analysis of the
gas, and had given the mechanical equiv-
alent of a unit of the same both in the
pure and diluted state. If the explana-
tion had then followed, that the mechan-
ical equivalent of the latent heat of ex-
pansion per unit of the gaseous mixture
per degree of temperature was nearly the
same as for atmospheric air, the reason
why the gas engine might be considered
in theory as an air engine would have
been clearer, namely, that the adiabatic
curve, or curve of no transmission of
heat, was nearly the same for both. The
author commenced by an attack upon the
steam engine. Much heat was required
in evaporating water whose specitic heat
was high, and hence the efficiency of the
steam engine was low, . and something-
better was needed ; whereas it was clearly
proved by Rankine, a quarter of a century
ago, that the maximum efficiency of a
theoretically perfect heat engine, working
between given limits of temperature,
was equal to the ratio of the range of
temperature to the higher absolute limit
of temperature, and quite independent
of the fluid employed. Raising the tem-
perature entirely by compression or using
regenerators were, the two means by
which the actual efficiency might be made
to approach the maximum limit. The
author believed in compression, but his
method of defence of it and his illustra-
tions of its advantages did not appear to
be quite correct. He took three types of
engine: the first and third were ^ex-
plosive gas engines ; the second was
worked at constant pressure, and these
he treated as air engines. The first and
second were -worked between the same
limits of temperature, but in the second
compression was employed. What the
author wished to prove by the theoretical
diagrams of these types was that the
constant-pressure engine using com-
pression was more theoretically perfect
than an explosive engine using none,
whilst an explosive engine using compres-

THE THEORY OF THE GA8 ENGIN E.

453

sion was th • best of tin three. Bui be
had shown by type No. 2, thai by the
>f compreasioD aij efficiency could be
attained higher than the maximum ef
ficiency of a perfect heat engine, which
Beamed to require Borne explanation.

T — T

J in ab-

The maximum was equal to

solute degrees of temperature, and was
for 1,537' Ontigrade and 1,089° Centi-
grade equal to 0.247 for both types ;
whereas the author mule it 0.21 for the
lii st and 0.36 for the second. The author
allowed that type No 1 would be im
proved by further expansion, but that
that would require a vacuum pump and
condenser; yet surely il nude no differ-
ence, so long as they both consumed the
sam i quantity of heat, whether a com-
sion pump was use 1 at the beginning
or a vacuum pump at the end of the
stroke, whilst indeed there might be theo-
retical reasons in favor of the latter.
Types 1 and '6 were respectively worked
without a' id with compression ; they were
both explosive engines, and the efficiency
of the litter was made double that of the
former, but the latter was made to dis
ge at 6480 Centigrade, and tue
former at 1,089° Centigrade. If these
figures had been reversed, so would have
i the efficiencies. H id the author
explained that there was a certain maxi-
mum efficiency for heat engines, and that
by means of compression a larger per-
centage of that maximum could be at-
tained than without it, t iere would have
been no re ison for objection ; but that
was a very different thing from trying to
show that it was possible to obtain more
than the maximum efficiency of a theo-
retica ly perfect heat engine.

Th • re 1 value of the gas engine was,
that it contained the furnace and engine
in one; thus the necessary h at lost in
the furnace to make a draught, and the
unnecessary loss of heat by radiation
from a la ge steam boiler were both
avoide I in the gas engine, and, finally,
the gas engine could be used safely at
a maximum limit of temperature, which
cou d not be employed in ihe ste m en-
There was no doubt a gre it future
for this cl iss of motor.

Sir William Thomson said that he had
recently seen a very interesting experi-
ment made by the author with a gas

engine at Glasgow, which he thought had

a most important bearing on the mod;' of

ation of the gas in the cylinder. The

experiment was made in the presence «>t'
his brother Professor .James Thomson
and Professors Jack and Ferguson i of

Mathematics and Chemistry in the Uni-
versity of Glasgow), who were all much
interested in the inquiry. The object

was to test the nature of the mixture in
close proximity t > the piston, so as to be
able to form some idea as to whether or
not the explosion took place through the
whole spa -e ; to be judged by finding
whether, right up to conta-t with the
piston, gas and air were present in pro-
portions suitable for combustion. He
need not enter into details as to the way
in which the experiment was made, but
he might say, iu a general way, that while
the piston was being pressed in to con-
dense the mixture at a detinite point of
the stroke, communication was made with
the cylinder. The small experimental
cylinder and piston were placed in proper
position, in communication with an aper-
ture bored for the purpose in the main
cylinder. The author of the paper
would be able to explain the details better
than Sir William Thomson could. It was
sufficient to say that by an automatic
arrangement, worked mechanically from
the cross-head, the communication was
made exactly at one definite point of the
stroke, and the experimental piston was
pressed up in the cylinder so as to let it
till. At any time afterwards the stop-
cock could be opened by hand, and the
nature of the contents tested. In every
case the contents were found to be ex-
plosive - an explosive mixture of gas and
air — proving that up to the very point,
which he und rstood was within about an
inch from the piston, coal gas was present
in suitab-e proportions for producing an
explosion. There was one other matter
t > whi h he wished to refer, which had
been noticed in the discussion. There
appear d to be some differ en e of opinion
upon it, but to his mind it scarcely ap-
peared open to doubt that the diagram,
which showed an exceed'ngly su lden r se
and a gradual f dl, proved that combus-
tion was practically complete at a point
corresponding to the summit of the
curve. Li erally and precisely the instant
of the maximum of the curve was that
at which the rate of loss of pressure by

454

VAN nostrand's engineering magazine.

expansion, the much smaller rate of loss
of pressure by loss of heat carried by
convection of the fluid to the solid boun-
dary and out by conduction through the
metal, were exactly counterbalanced by
the rate of combustion still going on. It
seemed certain that the rate of loss by
the two causes he had indicated was ex-
ceedingly sma1! in comparison with the
rate of rise by the initial progress of the
explosion ; therefore, practically speaking,
the maximum of the curve indicated truly
the instant when the combustion was as
complete as dissociation at the highest
tempearature attained allowed it to be.

Mr. D. Clerk, in reply upon the dis-
cussion, said that two of the speakers
seemed to think that the question at issue
was one of infringement of patent, but
he desiied to arrive at the truth, apart
from mere questions of personal interest.
The question of infringement was to him
one of complete indifference.

The question he was anxious about
was the purely scientific one. Was his
theory of the action of the gas engine the
true one, or was it Mr. Otto's ? This mat-
ter might appear to some persons a small
one, but he considered ilf of vital interest,
being convinced that not many years
hence the gas engine would have a science
of itte own, and scientific names connected
with it as much honored as any ever
linked with the steam engine. Dr. Sie
mens had fully corroborated his view of
dissociation, and in the effect it had on
the gas engine diagram, in preventing the
more rapid fall, which must otherwise
occur ; but he did not agree with him in
the necessity for further research on dis-
sociation, believing that St. Claire
Deville's work was sufficient. Dr. Sie-
mens would observe tLat St. Claire
Deville's researches were referred to in
the paper; but what he asked for had
never to his knowledge been published,
that was a complete curve of the dissoci-
ation of water and carbonic acid. St.
Claire Deville's results were more of a
qualitative than of a quantitative nature.
He feared that the method used was not
capable of the necessary accuracy.

He thoroughly believed that the engine
for the very large powers to be construct-
ed in future must be of one type 2, with
hot chamber or cylinder, and regenerative
contrivance in some form ; indeed, about
two years ago he constructed and experi-

mented with such an engine, and he was
continuing his experiments.

The mechanical difficulties were much
greater than in the cold cylinder, type 3.
It must be remembered that the cold
cylinder gas engine was the engine of the
present, and it was most satisfactory that
even with the small sizes so high a duty
should be obtained. It proved that when
larger engines were made a much higher
duty might be expected. The theory of
the cold cylinder engine did not allow of
the application of any regenerative con-
trivance, and consequently arrangements
must be made to ,get the greatest possi-
ble fall of temperature due to work done.
A very interesting account had been
given by Professor Rucker of his view of
the problem, and the necessity of correct-
ing the calculations of previous observers
in the light of present knowledge of the
laws of combustion had been demonstrat-
ed. It was satisfactory that Professor
Rucker so thoroughly agreed with him
on the necessity for considering dissocia-
tion in any theory of the gas engine, and
had independently arrived at similar con-
clusions. The experiments of Messrs.
Mallard and Le Chatelier corroborated
those of Professor Bunsen in this, that at
the high temperature of combustion, a
large amount of heat was rendered latent.
So striking a fact could hardly have
escaped the notice of many other experi-
menters who might not have published
their results. He had noticed it about
five years ago, while making experiments
on the maximum pressure obtainable from
a pure explosive mixture of gas and air.
A cylinder 9 inches in diameter and 9
inches long, was filled with a mixture of
gas and air in the proportions for maxi-
mum explosive effect, and ignited the
mixture by means of a hollow stop cock,
after Barnett's style of igniting arrange-
ment. With the temperature of the mix-
ture before ignition at 12° Centigrade,
the highest pressure attained was 97 lbs.
per square inch above the atmosphere.
The pressure was measured by a loaded
valve of known area, as in Bunsen's ex-
periments. The absolute pressure attain-
ed was only about 7^ atmospheres ; if
complete combination had taken place,
and no heat kept back by dissociation or
absorbed by change in specific heat, then
the pressure should have been at the low-
est estimate, 11 atmospheres. He con

THE TIIKoKY OF THE G LS I \<-IN I.

455

eluded that Prof essor Bunsen's explana- [n the paper he had not detailed the method
tion of this fact was a true one. The used to calculate the temperature attained
effect was equally visible in the large at the point of maximum pressure j it was
oylind t used by him and in the small Decessary to do bo before proceeding fur-
tube used by Pr ifessor Bunsen. These ther. First, he determined the ei

periments, and the recent experiments volume of the space at the end of the cy-

of Messrs. Mallard and Le Chatelier, make Under into which the mixture was com-

pressed, then on the
drawn the adiabatic line
it was the dotted line
the lower black line wns

rtain that in a uniformly ignited gas-
eous mixture the temperature was limited,

ami the apparent loss of he.it was very
slow, ami that this effect was due to dis-
sociation, either complete or incipient.
Such a mixture in expanding during work

lid give rise to all the phenomena de- ly as possible coincident.
scribed in the paper. He was pleased this had been pointed out
that his conclusions on the relation be-
tween rate of inflammation at constant
pressure and constant volume had been
experimentally proved by these gentle-
men. He had been challenged by Mr.
Imray to controvert his statement on the
>ry of the introduction of the gas
This he did not do, because he
*ed Mr. Imray 's account fairly

diagram

of
shown at Fig

he had
compression,

the actual com-

conside
eorr

The only remark of Mr. Imray on his
theory was : " He would only refer to
Fig. 9. If the theory of dissociation
were true, it would follow that the lower
the temperature the more dissociation

pression line drawn by the Indicator. It
would be seen that the two were as near-

The cause of
The temper-
ature at the point c was known to be
150°.5 Centigrade, and the pressure 41
lbs. above atmosphere, and assuming the
volume to remain constant, the tempera-
ture at a, was calculated from the press-
ure 220 lbs. above atmosphere.

Let P=: pressure before ignition, and
P' pressure after ignition, T = tempera-
ture before ignition and T' temperature
after ignition, then —

P' T

rp/ * _

both pressures and temperature absolute.

In diagram Fig. 1 it was shown that the
would take place, which was undoubtedly temperature of compression, correspond-
altogether wrong." It was difficult to ing to 40 lbs. above the atmosphere, was
understand this statement, it was so ex- 150°. 5 Centigrade, and from these figures
ceedingly irrelevant He could hardly the temperature 1,537° was obtained.
believe the spe.iker had ever studied the This was the minimum possible tempera-
pressure, volume, and temperature rela- ture, as would be observed from certain
tions of gases. On the indicated diagram considerations developed at p. 21.
low7 pressure had been mistaken for low Whether the name had spread through-
temperature, neglecting the increased out the mass of the mixture or not, this

volume due to the travel of the piston.
Mr, Imray had supposed that the maxi
mum pressure on line d (Fig. 9), being
lower than on line a, therefore the tem-
perature was also lower. He failed to
see the bearing on the theory under dis-
cussion of Mr. Bousfield's statement :

Fig

was the average temperature. From a,
19, was drawn an isothermal line, a
dotted ; at the point a the tempera-
ture had commenced to fall, up to that
point it had been rising at a very rapid
rate. The semicircle drawn below the
atmospheric line showed the path of the
11 He did not say that when the explosion crank-pin, and each division represented
took place, there might not be a certain in time one-fiftieth of a second ; the en-
quantity of ammonia and a certain quan- gine was running at one hundred and fifty
tity of nitric acid formed." The question revolutions per minute when the diagram
why, when maximum pressure was reach- was taken. Comparing the condition of
ed at the beginning of the stroke, he as- the gaseous mixture in one fiftieth of a
sumed that the flame had spread through- ■ second before maximum pressure, and
out the mass in the cylinder was much one-fiftieth of a second after maximum
more to the point. From the original of j pressure, in the first one-fiftieth of a
the diagram. Fig. 6, he had taken the two second the average temperature had in-
extreme lines shown at diagram Fig. 19, a creased 905° Centigrade, while in the
and b were the points of maximum pressure, second hundredth it had diminished about

456

VAN NOSTRAND fe ENGINEERING MAGAZINE.

] 89° Centigrade. "Within a limit of one
twenty-fifth of a second there was a point
where the increase of temperature ceased,
and where a fall of temperature began.
What did this mean ? Why did the in-
crease of temperature cease in so sudden
a manner and a fall of temperature set
in?

From the point d to a the temperature
had been increasing, this increase being
due to the progress of the flame ; at the

f the volume had changed so slightly that
the rate of cooling con Id not have in-
creased appreciably. The amount of
work done in that movement was also
relatively insignificant, and yet from some
cause the increase of temperature going
on with such rapidity, 905° in one-fiftieth
of a second, had not only diminished, but
an opposite effect had set in. It could
not be supposed for a moment that the
progress of the flame had been abruptly

Engine speed 150 revolutions per minute.

One division of circle =one-fiftietu part of a second at above speed.

point a the increase ceased, and a fall set
in. Take the point e, then the average
temperature was 632° Centigrade ; from
e to a the time taken one-fiftieth of a
second, and the temperature rose to
1,537° Centigrade; in that time it had
increased by 905° ; suppose the same
rate of increase to continue for another
one-fiftieth of a second, the pressure
would rise to the point /', and the tem-
perature would be 2,442° Centigrade, the
points g and h showed the effect of fur-
ther increase. But the increase Lad
abruptly ceased at the point a ; from a to

stopped by any cause other than com-
pleted inflammation of the whole mass.
The flame which in one instant o£ time
had been flashing through the exp'osion
mixture had reached the enclosing walls,
it had uniformly heated the whole com-
bustible mass, and in the next instant the
temperature b. gan to fall ; the law of
cooling took effect. The very rapid rate
of rise, and the abrupt change from rapid
rise to slow fall of temperature, at a given
point, showed that at that point completed
inflammation had been attained. '1 he
cooling which was so slow as to be unable

THE niKoKY OF THE G L8 ENGINE.

457

to put an appreciable chock on the rate of
rise up to the point of maximum temper
ature, could not be supposed to suddenly
increase to such an enormous extent as to
mpletely absorb and overpower at thai

instant the effect of continual spread of

flame. There could he no doubt that, as

Sir Thomson had pointed out, on diagram

. the maximum of the curve indicat-

truly the instant when the COmbus

tion was BS complete as dissociation

allowed it to be. It was certain that at

this point of the diagram the flame had
Bpread completely through the whole
volume of inflammable mixture, and that
in whatever way the sustaining of the
pressure to nearly the adiabatic line was
to be explained, it could not be accounted
for on the hypothesis of a continued
spread of flame.

A little consideration of the conditions
of the indicated diagram would show that
the slower the rate of inflammation, rel- 1
atively to the movement of the piston, j
the less distinct would the point of maxi-
mum pressure become, and the more
rounded would the apex of the diagram
appear-. Nevertheless the point of com-
pleted inflammation was easily deter-
mined from the point of maximum tem-
perature, when near the end of the stroke
this point might not be the point of maxi-
mum pressure. He had been careful to
make this distinction, and had said, with
reference to slow inflammation, p. 25 :
M This supposed phenomena has been
erroneously called slow combustion ; if it
has any existence it should be called slow
inflammation. It has a real existence in
the Otto engine only when it is working
badly -. but even then maximum tempera-
ture is attained, and very distinctly marks
the point of completed inflammation."
On diagram Fig. 19 was shown the effect
of increasing the speed of the engine
while preserving a constant rate of in-
flammation. If the speed were increased
from one hundred and fifty revolutions
per minute three times, or to four hun-
dred and fifty revolutions per minute, it
would be found that the point a would
be moved forward to k and b to I. In
both cases the temperature attained
would be nearly 1,537° Centigrade, a
slight fall would be observed due to in-
creased cooling surface and to a part of
the work being done before maximum
temperature was attained. But in all
Vol. XXVII.— No. 6—32.

88 the maximum temperat lire marked

the point oi completed inflammation and
the temperature began to fall so soon

it was attained. For ignitions attaining
their maximum very late in the strol

maximum pressure need not coincide with
maximum temperatures j but a reference

to the isothermal line showed the point
of highest temperature. I sing an in-
flammable mixture of constant oomposj
tion. and varying the speed of the engine,
it was always found that ignitions at-
tained maximum temperature later and
later in the stroke always came very near
the isothermal line drawn i'roni the point
of highest pressure at the beginning of
the stroke. The lines never ran over this
isothermal. This meant that, whether
inflammation was completed early or late
in the stroke, nearly the same maximum
temperature was attained. It followed
from the relations between isothermal
and adiabatic lines, that the lines drawn
by the indicator from late ignitions always
crossed those from early ignitions. This
was shown by the diagrams taken from
an Otto engine by Mr. Bousfield, for
which he must thank that gentleman. In
these diagrams, however, it was evident
that the mixture used had not been of
constant composition at all speeds. This
would be evident by examining Fig 15.
When the speed had been changed from
one hundred revolutions per minute in
the larger diagram to two hundred in the
smaller, the increased speed of the engine
had caused it to take in a smaller weight
of gaseous mixture, as was shown by the
compression line leaving the atmosj>heric
line later, and that the pressure on com-
pletion of the in stroke only rose to 22
lbs. per square inch instead of 30 lbs., as
in the other. If the mixture had been
the same the point of maximum pressure
would have crossed in the first diagram
at this point, and the pressure line would
have run into the first lower down,
was shown in his diagram at />, Fig. li).
In the Otto engine the hot exhaust re-
maining in the space when each cycle wa^
completed still further complicated the
comparison between different speeds. At
the higher speeds the walls of the cylinder
had less time to cool the exhaust, and
consequently the average temperature of
the mixture before compression must be
greater at high speeds. In his own gas
engine this complication had no existence,

458

VAN nostrand's engineering magazine.

because the whole charge was replaced at
every stroke. In Mr. Bousefield's dia-
gram, Fig. 16, the same change of mix-
ture was evident, but here the change of
speed of the engine was relatively greater,
and consequently the lower diagram
crossed the upper one somewhat earlier.
In Fig. 17 this was more and more evi-
dent ; still no two of the compression
lines coincided, showing the proportion
of exhaust to inflammable mixture to be
continually increasing, and the maximum
temperature attainable by the ignition
consequently becoming less and less.
Even in diagram, Fig. 18, maximum tem-
perature was attained, and could easily be
discovered by calculating the average
temperature at each point along the line
of increasing volume. Mr. Bousfield
stated that a light applied to the exhaust
of an engine, giving diagram, Fig. 16,
caused explosion, and from that inferred
that combustion was not completed at
the end of the stroke. He would find
that when this happened the engine was
missing ignition altogether and discharg-
ing the unburned contents into the ex-
haust. He might observe that the hor-
izontal line in that diagram did not
mean constant temperature, but indicated
constantly increasing temperature. Mr.
Bousneld has evidently fallen into the
same error as Mr. Imray, and confound-
ed low pressure with low temperature
without considering the change of vol-
ume. It was a characteristic of the in-
flammation of a gaseous mixture in mass,
that so long as inflammation continued
to spread, so long did the average tem-
perature increase. Dissociation did not
begin to sustain temperature until the
temperature fell. In the construction of
the theoretical diagram Mr. Bousneld
had fallen into error. He drew from the
points F G H, Fig. 14, to A L produced,
lines which he described as adiabatics,
and then said that the curve drawn
through P Q E "represented the press-
ure at any time in the contents of the
cylinder, supposing these contents remain
confined in the space at the end of the
cylinder, and not allowed to expand."
Now the lines F G H should not be
adiabatics but isothermals, as Mr. Bous-
field's object in constructing the diagram
was to get the time taken in a closed
space to attain the temperature existing
in the engine at the points F G H.

The points L M N should show the
pressure at constant volume at these
temperatures. If Mr. Bousfield calcu-
lated the temperature from an actual
diagram, he would find that maximum
temperature coincided with maximum
pressure when at the beginning of the
stroke. He thought from his remaining
criticisms that Mr. Bousfield had not un-
derstood the nature of the proof advanced
in the paj^er, and that when he had
studied the subject and appreciated the
nature of the considerations advanced, he
would admit the truth of the theory set
forth in the paper.

It had been asked by Dr. Hopkinson
whether the pressure rose higher when
an engine was running slowly than when
it was running fast 1 Whether the press-
ure attained on exploding a gaseous mix-
ture in a closed space and in an engine
was the same ? Given the same propor-
tion of gas to ah and the same tempera-
ture and pressure of mixture before igni-
tion, then the pressure attained after ig-
nition was the same in all stages where
the maximum pressure was attained at
the beginning of the stroke ; it was the
same whether in a closed space or in an
engine. But the ignition must be rapid
enough at the higher rate of speed to
give maximum pressure at the beginning
of the stroke. As he had already pointed
out, if an engine was to run fast enough
it might overrun the rate of inflammation,
and the maximum temperature would not
be attained till towards the end of the
stroke. If an engine was run at two
hundred revolutions per minute and max-
imum pressure was attained at the begin-
ing of the stroke, then however slowly
that engine ran using the same mixture,
the maximum pressure would always be
the same, it would not increase. Dr.
Hopkinson then asked, Was the maxi-
mum pressure the same in large and in
small engines ? When using a similar
mixture, the -same pressure and tempera-
ture before ignition, it was the same. In
small engines the temperature fell more
rapidly than in large ones because of the
greater proportion of cooling surface to
volume of gases, but the maximum press-
ure attained was nevertheless the same
because of the rapid rate of ignition. The
results obtained in the large cylinder to
which he had alluded, and those obtained
by Professor Bunsen in a small tube,

THE THEOBY OF THE G L8 ENGIH E.

4f)9

each showing a limit to tlio rise of tem-
perature which could not be referred to
cooling, and each Bhowing complete
Bpread of flame, proved thai the maximum
pressure t i be obtained Erom an explosive
mixture was independent of the dimen-
sions of the vessel need. Dr. Hopkinson
had asked why, in comparing types 2 and
'A of engine, he used different maximum
prefigures . why in the second type he
used 76 lbs. per square inch above the
atmosphere, and in the third over 200 lbs.
per square inch. His reason was this:
the three types were taken under coiuli-
- which have byen found in practice
to be the most favorable for each. He
ha 1 compared the theory of these types
of engine as nearly as possible under con-
ditions used in practice It was quite
true that type 2 should be compared with
type 3 under similar conditions of press-
ure from a purely theoretic standpoint ;
but the object of the paper had been to
inquire into the cause of the greater effi-
ciency of the third type as in use against
the two first also in use. It would be
seen that to attain a pressure of r200 lbs.
per square inch in type 2 it was necessary
to compress the mixture to that pressure
before ignition, the temperature of com-
pression being nearly 365° Centigrade
This involved considerable loss of heat in
the reservoir, and increased the chances
of leakage while compressing ; in type 3
a pressure of 40 lbs. per square inch be-
fore ignition was all that was required to
attain 200 lbs. after ignition. He believed
that type 2 could work advantageously at
a much higher pressure than 76 lbs. per
square inch, but he questions whether it
could do so at so high a pressure as 200
lbs. 'Ihe advantage of type .'> in this
respect was a comparatively low pressure
before ignition. With careful workman-
ship doubtless it would be possible to use
an engine of type 2, the theoretical effi-
ciency of which would be quite as much
as type 3, as given in the paper.

The description by Mr. F. H. Wenham
of his work on hot-air engines was inter-
esting, and his distinction of the cylinder
itself as the heat generator or furnace
was the essential one between gas and
hot-aii* engines, and was indeed the great
cause of success in these engines. Mr.
H. Davey had objected to his com-
parison of the efficiency of gas and steam
engines, and considered the basis of com-

parison of efficiency used by him as an
unfair one. In comparing engines of the
same system it was right, as Mr. Davey
stated, to use as the standard the mechan-
ical equivalent of the total available heat :
but ill engines of totally different nature
the only basis of comparison was the
number of heat units given to the engine,
and the number of these heat-units con-
verted into mechanical work. If one
tem was necessarily limited in range of
temperature, as the steam engine was,
then the inquiry must not be how near it
approached perfection within that range.
but how much heat could another sys-
tem convert into work as compared with
it. In comparing steam engines with
steam engines Mr. Davey is perfectly
right ; in comparing with gas engines the
general basis must be taken. He agreed
that the speedy downfall of the steam
engine was not to be anticipated ; he
only held that the gas engine was now in
its infancy, that it contained greater
possibilities than the steam engine, and
that in the future it was certain to be in
; every way a great advance on the steam
: engine, and likely to supersede it.

The propriety of treating the gas en-
gine as an air engine had been called in
question, and he had been asked whether
the specific heats of air and the gaseous
mixture used were in any way comparable.
The specific heat of air at constant vol-
ume was 0. 169, and the specific heat of a
mixture of 1 volume of coal gas and 12
volumes of air could not exceed 0.200, so
that for the purpose of approximate
comparison their adiabatic curves might
be considered as nearly identical. So
little was known of the specific heat of
gases at high temperature that. Mr. Clerk
considered it simply an affectation of ac-
curacy to endeavor to make the com-
parison closer. He was aware that the
efficiency of a heat engine was independ-
ent of the nature of the fluid employed,
provided the temperatures between which
the engines worked were the same —that
was provided there was the same differ-
ence between source and refrigerator.
But this was just where the steam engine
failed. Given equal amounts of heat from
the same source, in the ste.im engine the
high temperatures could not be utilized,
because, first, a certain quantity of heat
had to be expended to change the ph
, ical state of the water : and as the steam

460

VAN nostrand's engineering magazine.

produced was rejected as steam all the
heat so expended was lost for the pur-
pose of procuring high temperature.
"With air, on the other hand, the same
quantity of heat from the same source,
a much higher temperature was attained,
and consequently a greater range of tem-
perature due to work performed. The
use of steam necessitated a limited range
of temperature, and the discharge of all
the heat used in converting water from a
liquid to a gas. It had been argued that
in engine type 2 he had over-estimated
the efficiency, and made it greater than
was possible from a perfect heat engine
working between the limits of tempera-
ture used. Mr. Bamber had fallen into
error by mistaking the limits, and in this
he was not alone. This type of engine
presented very interesting peculiarities in
theory, which, so far as he was aware, had
hitherto been missed by writers on
therrao- dynamics. Although 1,537° Centi-
grade was the maximum temperature,
and 1,089° Centigrade the temperature
of discharge with the exhaust, yet these
temperatures were not the limits within
which the engine was working ; the re-
frigerator, which was at atmosphere
temperature 17° Centigrade, was being
uslc! to a certain extent without being
apparent.

The diagram was not a simple one ; the
efficiency 0.36 was the result of the united
action within two different limits. The
diagram from 1,537° Centigrade to 1,089°
Centigrade was the same both in types 1
and 2, and working between these limits
the maximum possible efficiency was
0.247 ; but in type 1 this efficiency was
not attained, because at 1,089° Centigrade
the air had not the same density as be-
fore expansion, and some work had been
expended in changing the volume to twice
its original amount. If before heating
the air had been compressed slightly,
then heated to 1,537° and expanded to
its original volume, and lowered in tem-
perature due to work done to 1,089°, the
duty would be 0.247. If in type 1 a con-
denser were used, and the temperature
reduced to 17° Centigrade, the additional
work obtained would raise its duty to
0.247, without this it remained at 0.21.
In both types the efficiency between the
limits 1,537° Centigrade and 1,089° Centi-
grade was the same ; but in type 2 a con-
siderable amount of work was obtained

in the earlier part of the diagram, a cer-
tain amount of work was done on in-
creasing temperature from 217°. 5 Centi-
grade to 1,537°, and a considerable pro-
portion of heat could be converted into
work on an increasing temperature, still

T -T

conforming to the law ' 2 as the

maximum possible between the limits.

In type 2, to a certain extent, the re-
frigerator at atmosphere temperature was
made available in a portion of the action,
and consequently a portion of work done
on increasing temperature, while the latter
half of the stroke was accomplished on
falling temperature. This was the
reason why a greater efficiency was got
than the apparent limits would allow.
Mr. Bamber then argued that it made no
difference whether it was necessary to
use an air pump or not, if only the same
quantity of heat were consumed and the
same theoretic efficiency obtained. In
practice it made all the difference ; the
great cause of failure with hot-air
engines was not imperfect theory but
very low available pressures combined
with high maximum pressures. Nearly
all the power indicated was used up in
friction ; in the earlier gas engines the
average pressures were very low also.
The advantages of compression were a
high available pressure, small cooling
surfaces, and small loss by friction.
There the efficiencies depended on the
range of source and refrigeration; but
compression allowed all this to be at-
tained under practical conditions. It was
hardly necessary to explain that there was
a certain maximum efficiency for heat
engines. What he had shown in this
paper was that a greater proportion of
this was possible under working con-
ditions with compression than without.

The parallel by Mr. Cowper between
slow inflammation and imperfect admis-
sion of steam in a cylinder was very just,
and illustrates the great loss of power
and heat involved by imperfect mixing
of gas and air, or by failing to attain
maximum pressure as soon after firing as
practicable. It was only by a constant
application of theory to practice, and a
constant testing of results obtained by
varying conditions, that he had been able
to produce the diagram which Mr.
Cowper approved. The amount of gas
consumed by his G-HP. engine was 22

HOUSE DRAINAGE AND SANITARY PLUMBING.

461

cubic feel per I HI*, per hour, Of course

in cost this did UOt Stand comparison

with the coal used by a large modern
steam engine: the steam engine had
greatly the advantage ; hut compared with
a sinail steam engine u was economical.
When gas was manufactured expressly

foi it need cost bnt'little

more than the coal used to produce it,

ami as the gas need not he illuminat-
ing all the carbon might he converted
into gas. The gas might be in fact a
mixture of carbonic oxide and hydl

gen.

HOUSE DRAINAGE AND SANITARY PLUMBING.

By WM PAUL GERHARD, civil and Sanitary Engineer, Newport, K.I.
Contributed to Van Nostrand's Engineering Magazine.

III.

PLUMBING FIXTURES.

The various plumbing fixtures which
receive and deliver to the drain the foul
wastes of the household, will be reviewed
here only from a sanitary point of view.
For more detailed technical descriptions
of plumbing appliances I refer to the
interesting series of articles on "Modern
Plumbing," by T. M. Clark, Esq., in the
Ann Vrchitect for 1878, and to nu-

merous papers on "Plumbing Practice "
in the Sanitary Engineer.

Plumbing fixtures should be concen-
trated in a house as much as possible, so
as to render necessary only few vertical
stacks of soil and waste pipes, and to
avoid long horizontal runs of pipes,
which are objectionable inside floors,
nr>t, because they necessitate the cutting
of beams ; second, because they prevent
the running of waste pipes with proper
fall. Much may be effected in planning
a new building in this direction by a
proper attention of architects to its
drainage system.

To householders and persons about
to build a house I would give the gener-
al advice to have only few plumbing fix-
tures, as few as they can possibh
along with, but to have these of the very
best quality and fitted up in the very
best manner. It is much better to have
only one water closet in a house, used
constantly by all its occupants, and
therefore frequently flushed, than to have
half a dozen or more, each used only
little.

It has recently been proposed by some,
in view of the danger to health

from defective plumbing, to arrange all

fixtures in an annex, separated from the
living and sleeping rooms of the house.
This would be not only inconvenient but
impracticable in cold climates and seems
entirely unnecessary. All that needs to
; be done is to remove plumbing fixtures
from sleeping rooms, as sewer gas enter-
ing these through leaky joints or defec-
tive traps and fixtures, would be much
more dangerous to persons inhaling it
during sleep than during hours of active
exercise. Wherever possible, it is desir-
able to locate water closet apartments
and slop sink closets so as to be cut oft*
from the main part of the house. This
would involve the separation of the water
closet from the bath room, such as is
common in Europe, but little known in
this country, and which arrangement I
am inclined to favor, especially in the
case of a house, occupied by a large
family, and having only few plumbing
fixtures.

If proper regard were paid to the
ventilation of rooms, containing plumb-
ing fixtures, the risk from sewer gas
would be infinitely reduced. Unfortu-
nately, it has hitherto been the habit
with most people to care more for the
bright look of their fixtures, for decora-
ted china ware, costly marble slabs,
silver-plated faucets, chains and tubs,
for handsomely finished woodwork
around bowls, water closets, sinks, than
for the proper trapping and ventilating
of such apparatus. Tight woodwork
around bowls, tubs, sinks, slop hoppers
and water closets, which is the rule in
ninety-nine out of every hundred houses,
forms harboring places for vermin: they
in time accumulate dust and become ex-

462

VAN NOSTRAND'S ENH I PEEKING MAGAZINE.

ceedingly filthy, damp and foul smelling.
The encasing of plumbing fixtures should
be discouraged for sanitary reasons.
Dampness and nasty odors can be prevent-
ed by keeping such spaces entirely open
so that a free current of pure air sweeps
around the fixtures, the most remote
corner of which is thu^ made accessible
to servants for cleaning purposes. But
even with good sanitary appliances, prop-
erly ventilated and connected with self
cleansing traps and waste pipes the
householder should not forget that con-
stant care and watching is imperative, as
well as a thorough cleansing and scrub-
bing as often as once a week and prefer-
ably oftener.

Sufficient hints will be given in the
following pages as regards the merits
and defects of the various plumbing fix-
tures, especially the different types of
water closets, to guide the householder
in selecting proper and satisfactory ap-
pliances. In regard to the selection of a
proper water closet — and, in fact, of every
plumbing fixture — a certain embarrass
ment arises to every householder, in so
far as almost every manufacturer natur-
ally thinks his goods the best and safest
to be used. Should the householder be
unable to make a selection from his own
judgment, he should consult an architect
or sanitary engineer of reputation.
Should he decide from personal opinion
and examination of closets, let him bear
in mind that closets almost without ex-
ception present a good and cleanly ap-
pearance in manufacturers' showrooms.
The real test of the efficiency of a water
closet is some months' severe use in a
frequented place (which, however, should
be under constant supervision of a jani-
tor). In this connection I would advise
to choose none but the very best appara-
tus for the use of the servants. A ser-
vants' water closet is likely to receive a
rougher treatment and less cleaning than
closets for use of the family ; closets
with movable machinery (pan, valve and
plunger closets) are especially objection-
able, as they frequently get out of order;
no cheap kind of hopper should be used.
An automatic flushing arrangement for
servants' and children's closets will se-
cure better cleanliness than arrangements
to be worked by hand.

In speaking of water closets in gener-
al further points of importance for the

selection of such apparatus will be men-
tioned.

WASH BASINS.

Beginning with wash basins, little of
sanitary importance may be said with re-
gard to them. If properly fitted with
waste pipes of proper size and material
aud efficiently protected by a good trap,
they may be considered perfectly safe
conveniences in dressing rooms. Their
use in sleeping apartments, and in closets
or boudoirs near bedrooms without in-
dependent ventilation, is attended with
considerable risk, and the habit of put-
ting stationary lavatories in such rooms,
which has become so general nowadays,
should be earnestly discouraged, especi-
ally for such rooms, as are not continu-
ally occupied (summer residences, hotels,
&c).

Wash basins are mostly made in earth-
enware, this material being the cleanest
and best for the purpose. Iron works,
however, manufacture cheap iron wash-
stands, plain, painted, galvanized, or
enamelled, which may answer for office
use, for prison cells, &c. Copper basins
are rarely used.

Earthen bowls are attached by brass
basin clamps to marble slabs, the joint
between them being made tigh t by means
of plaster- of-Paris. To prevent damage
to ceilings the bowls are provided with a
number of holes near the upper rim, lead-
ing to a short horn, to which the lead
overflow pipe is attached. Some bowls
have a " patent " overflow, a concealed
channel in the side of the bowl.

The outlet of bowls is commonly closed
by means of an india-rubber, brass, or
plated plug, to which a chain is attached.
The annoyance caused in lavatories of
public places by too frequent breakage
of the chain, necessitating the removal
of the plug by placing the hands into
the dirty water of the bowl used by
some unknown person, has led to the
invention of a number of valve wastes
for bowls. In most of these, as for
instance, McFarland's, Foley's, Boyle's
valves and the Boston waste, the outlet
is closed some distance away from the
bowl, thus leaving the bowl in connec-
tion with the valve chamber, which, after
each use, remains coated with soapsuds
and foul slime. At the next use of the
bowl the clean water will mingle with this

HOUSE DRAINAGE AM) samtaiiv PLUMBING.

403

waste matter and become Boiled even be-
fore use. Moreover, the valve ohamberfl

get more or less foul after use, and emit
noxious smells into the rooms.

The only device whieh closes the howl
directly at its bottom is M Weaver-

waste." By simply touching a knob,

connected with a lever, the Btopperin the
bottom of the howl is lifted and held in
phi'

Jenning'fl M fcipnp basins" also do away

with chain and ping and are very ecu

it for use, as the basin is emptied

by simply tilting n, thus discharging its

contents into a bowl underneath, which

oncentric with the upper basin, aud

which the trapped waste is attached.

It appears at first sight to be a cleanly

device, but it gradually accumulates foul-

ness in the lower basin, which receives

no special cleansing, and for this reason

tip up basins are not to be recommended,

except where a stricter regard to cleanli-

>f plumbing fixtures is paid than is

usual in most households.

'L'he objection raised against most
valve wastes for bowls, namely, that the
walls remain coated with a more or less
foul slime after emptying the bowl, is
also true in regard to the bowl itself. In
private houses these are, of course, well
taken care of and daily cleaned; but in
public lavatories, used rapidly in succes-
u. a decided lack of cleanliness is
felt. An entirely newT departure in wash
bowls, so far as this country is concerned
— for it has been manufactured and sold
in England— would be a flashing rim
lavatory boicl, supplied with hot and cold
water through a nozzle, to which both
supply pipes are attached. By opening
either faucet, hot or cold water, as desired
would enter the bowl, simultaneously at
all sides, and give it a thorough down-
ward rinsing flush. The outlet of bowl
may then be closed and the bowl filled
with clean water. With such a flushing
rim bowl some of the valve wastes
would become unobjectionable even to
the most fastidious.

To make the flushing rim lavatory
perfect in neatness and cleanliness, the
marble slab, to which the bowl is
clamped, should be supported by hand-
some brackets, leaving off all carpentry
underneath. The floor under the bowl
and the rear wall may be neatly finish-
ed in w^hite tiles, or in cement or ter-

ra/./o floor, so as to be impervious, thus

doing away with the safe Lining under
Death the "bowl. U tiling or a terra/zo

floor is considered too expensive, a

well finished hardwood floor should be
used.

'1 lie arrangement suggested for lilting
up lavatories applies equally to common
bowls. Hitherto more or less tight
woodwork has been used to encase the
space under wash bowls in order to hide
from view traps, supply and waste pipes.
safe linings, drip pipes, etc. Such tight
unveidilated spaces with dark corners
must necessarily accumulate dirt, and be
come damp from leaky fixtures, and nasty
in general. With first class plumbing
work it is unobjectionable to have lead
pipes and traps in sight : leakage is
easily detected, and cleanliness of ser-
vants better enforced where there is
plenty of light and air around a wash
basin.

BATH TLBS.

Bath tubs are made of wood, or wood
lined with galvanized sheet iron, o; with
zinc or heavy copper, tinned and plan-
ished, or nickel plated, of cast iron with
porcelain enamel, and of stone ware.
Any of these may be used, the selection
| depending chiefly upon their cost and
upon the personal preference of house
owners. For private residences copper
bath tubs are used more than any others,
the weight of the copper being from 16
to 20 oz. per sq. ft. for the best tubs.
, Enamelled iron tubs are also used ex-
tensively, especially in hospitals, asylums,
&c. The porcelain bath tubs, although
' perfectly non-absorbent, most cleanly
and attractive in appearance are not much
in use, being very expensive, heavy and
clumsy.

For bathing establishments enamelled
iron and copper tubs are not to be rec-
ommended, the former losing their
enamel by continued use, the latter being
easily knocked out of shape and requir-
ing constant attention to keep on them
a bright polish. In such places earthen-
ware tubs will answer very well, being
^ily cleaned, and as they are used rap-
idly in succession they do not chill the
water after the first bath, an objection
1 sometimes against marble or por-
celain tubs in private houses. Tubs in
bathing establishments are often con

464

VAN NOSTRANDS ENGINEERING MAGAZINE.

structed of brickwork, lined with slate,
or with white tiles or marble flags.

Many devices have been introduced to
do away with the chain and plug arrange-
ment of tubs, which device gets unclean
from soapsuds here as in the case of wash
bowls. Such improved bath wastes are,
for instance. Weaver's, McFarland's, Fo-
ley's, H. 0. Meyer's, Jenning's, Stidder's
and others. None of these is preferable
to the " standing overflow," a most sim-
ple and cleanly contrivance, consisting
of a tube of same bore with the bath
waste pipe, with a trumpet- shaped mouth
at its top, which tube is inserted in place
of the plug at the bottom of the bath
tub. It renders a special overflow pipe
unnecessary. The only objection, some-
times made against it, is that it may be
in the way while bathing, especially with
short, so-called " French " bath tubs.

While it is not my intention to consider
the supply of hot and cold water to fix-
tures in general, nor to discuss the rela-
tive merits of ground cocks, compression
bibbs and self-closing faucets, I must
briefly touch, for reasons that will appear
hereafter, upon the manner of supplying
water to bath tubs.

If the hot and cold "water faucets are
placed near the top of the tub, the hot
water speedily fills the bath room with
steam (although this can be partly over-
come by using a double bath cock with
only one supply inlet) ; the noise of
the falling water is also sometimes
objected to. To avoid this inconvenience
the supply has been made to enter the
bath, hot and cold water mixed, through
the same hole that serves as an outlet for
the foul water. Thus soapsuds and filth
coating the waste pipe and left there from
the time the bath was last used, mingle
with the clean water. Such a device is
unsanitary and must be utterly con-
demned.

If it is desirable to avoid the steam or
noise in filling bath tubs, the supply inlet
may be placed at the foot end of the tub,
near its bottom. An advantage which
this arrangement offers is that servants
cannot draw water into pails or pitchers
in a bath tub, a frequent cause of tbe
chipping off of the enamel of iron tubs
and the bruises made in the sides of cop-
per tubs. It appears, however, that such
a location of the supply inlet below the
water line of the bath tub is, in certain

cases, endangering the purity of the water
supply. This risk always occurs wher-
ever the bath tub is supplied directly
from the rising main and the pressure of
water is insufficient to supply at all times
the upper stories of city houses. The
American Architect of 1882, in calling
attention to this danger (which danger is
well known to exist in the case of water
closets flushed directly from the service
pipe), says, as follows :

" Thousands of fixtures are in daily
use which are liable to have their supply
fail altogether on certain days and hours,
or to have it withdrawn temporarily by
the opening of a faucet below. All such
fixtures are exposed to the worst conse-
quences of intermittent supply. If any
person having access to fixtures so placed
will try the experiment of opening a fau-
cet at the time of low water, the rush of
the air sucked back into the pipe will be
plainly heard, or by placing the finger
over the mouth of the faucet the inward
pressure can be felt. Even where the
head is considerable, an artificial lower-
ing may be, and often is, caused by the
opening of faucets in the lower stories,
which will leave a vacuum in the pipe
supplying the upper fixtures, and in such
cases substances near the mouth of the
upper faucets are liable to be sucked
through them into the supply pipes. We
have known the opening of a pantry cock
in a lower story to siphon out in this
way and discharge into the pantry sink
the entire contents of a bath in a room
above, much to the amazement of its oc-
cupant. The bath happened to be fitted
with a bottom supply."

This may even happen with a supply
from a tank in the attic, and the only
means to prevent the occurrence would
be to run special lines of hot and cold
water from boiler and tank respectively
to the bath inlet, or else to place a check
valve in the cold water supply to the
bath, which remedy, however, cannot be
relied upon to work for ever.

There are many varieties of tubs, used
for personal cleanliness, such as foot
tubs, hip baths, bidets, shower baths, &c.
They need no further explanation, as the
principles for the sanitary construction
of bath tubs apply equally well to them.

Bath tubs of wood, lined with metal,
necessarily require some exterior finish-
ing woodwork, which also serves to hide

HOUSE DRAINAGE AND SAMTAKY PLUMBING.

4r>r>

from view the supply pipes, the overflow,
trap and waste pipe.
In Europe, metal l>:ith fobs arc made

sufficiently heavy to st:uul without a cas-
ing. This method of fitting op bath tubs
has much to recommend it from a sani-
tary point of view; such bath tubs stain 1
free on the floor, perfectly accessible and
with all pipes in sight, which seems en-
tirely unobjectionable. Iron porcelain
lined bath tubs are sometimes left with-
out woodwork in our hospitals and asy-
lums and give complete satisfaction.

LAUNDRY TUBS.

Laundry tubs are made of various ma-
terials, such as wood, wood lined with
sheet lead, enameled or galvanized cast
iron, cement stone, soap stone or earth-
enware. Wooden tubs are objectionable
as this material readily absorbs the dirty
water and becomes foul, emitting a close
odor when not in use. Being alternately
wet and dry they are liable to leak and
will quickly rot. Cement stone laundry
tubs are cheap, durable and cleanly.
They have ro seams, each tub being
manufactured in one piece, and therefore
will not leak. Galvanized or enameled
iron and soap stone trays are equally
good and much in use. The white crock-
ery or ik ceramic " tubs are undoubtedly
the neatest, and are always perfectly
clean and sweet. They are not subject
to wear or leakage, nor do they absorb
dirty water, and therefore do not become
foul from use. They are, of course, more
expensive than any of the others. Wood-
work about wash tubs should be dispen-
sed with as much as possible, and the
tubs treated in this respect as suggested j
in general for plumbing fixtures.

KITCHEN AND PANTRY SINKS, LAUNDRY AND

housemaid's SINKS.

Sinks are made of wood, of wood lined
with lead, or with copper, of cast iron,
which may be galvanized or enameled, of
copper, soap stone, slate or earthenware.

For pantry sinks tinned and planished
copper is generally used, being prefera-
ble to porcelain or soap stone sinks,
glass and crockery is not as liable to
breakage in them.

For kitchen and laundry sinks soap
stone or iron is much used. Galvanizing
or enameling the iron much improves the
appearance of the sinks, but even these

protective coating! wear off in time, and

then the iron rusts rapidly. Of late

earthenware sinks have been manufac-
tured up to large sizes and are un-
doubtedly the cleanest and neatest of all
kinds.

Housemaids' sinks, used only to draw
water, may be of small size and look most
cleanly when manufactured in earthen
ware, although other materials are often
employed.

Sinks should be provided with strong,
metallic strainers, either open or plug
strainers. In both cases the strainer
should be securely fastened to the sink
so as not to be removable by servants, in
order to prevent obstructions of the
waste pipe and trap. With plug strain-
ers it is important that the sink should
have an overflow pipe of sufficient capac-
ity to carry off the full supply, in case
the supply cock should be accidentally
left open.

In most houses kitchen sinks are en-
cased in tight woodwork, and conse-
quently a close, damp and foul smell is
often noticeable in the compartment un-
der a sink. This method of fitting up
sinks is decidedly objectionable, and the
common practice of using such unven-
tilated closed spaces under a kitchen
sink for the storage of kitchen utensils, or
what is worse, cleaning rags, etc., should
be strongly condemned. The space un-
derneath a kitchen sink should be free
to light and ventilation, and readily ac-
cessible for frequent cleansing. The
sink may be supported by brackets, prop-
erly fastened to the walls, or it may
rest on legs. The floor under the sink
and the rear wall may be finished with
white Minton tiles, which makes a neat
and most cleanly arrangement.

The remarks just made as to the de-
sirability of keeping the spaces under
sinks entirely open apply also to pantry
sinks and housemaid' s sinks.

GREASE TRAPS.

Through kitchen and pantry sinks a
large amount of grease, derived from
washing dishes, etc,, is emptied into the
drainage system. This grease proves to
be of all the waste matters in the house
the most difficult to deal with. Being
dissolved by hot water it passes the
strainer of the sink in a fluid condition,
but soon becomes chilled, adheres to the *

466

VAN NOSTRAND7S ENGINEERING MAGAZINE.

sides of the waste pipes or drains, lodges
in traps, and becomes putrid and offen-
sive.

If the drain inside and outside of the
house has a very good pitch, the grease
will probably be carried far away from
the house before becoming solid. This
is more likely to happen where sinks
have plugged outlets, as the rush of the
water carries the grease very far. The
ammonia of urine will remove grease,
and thus pipes receiving above the point
where the waste from the kitchen or
pantry sink enters the cellar drain a
water closet or urinal discharge are often
found to be comparatively free from
grease.

But in large houses, or hotels, &c , the
grease should not be allowed to enter
the house drain at all ; it should be inter-
cepted by a proper grease trap, placed as
near to the sink as the locality may per-
mit. The grease trap may be placed
either within the house, in the basement
or directly underneath the sink, or else
outside the house. The latter arrange-
ment is much the best, provided the
distance from the kitchen sink to the
grease interceptor is not too great, other-
wise the grease woulfl congeal on its
way to the interceptor. A circular tank
made of bricks, laid in hydraulic cement,
should be constructed of dimensions de-
pending somewhat upon the size of the
house. It should be large enough to al-
low the water time to cool. Its overflow
pipe consists of a quarter bend, or bet-
ter, of a T branch, dipping at least six
inches below the water line, in order not
to disturb the grease in the intercepting
tank. • This grease trap should be fre-
quently cleaned and inspected. The
grease, floating on top of the water, can
easily be removed. Efficient ventilation
by a large vent pipe should be pro-
vided. Wastes from kitchen and pantry
sinks only should discharge into the
grease trap.

If inside of the house and in the base-
ment, the grease trap may be made of
earthenware, of wood lined with heavy
lead, or of copper. But such a grease
trap in the basement cannot be recom-
mended.

If directly under the sink it may be
made of enameled or galvanized iron, of
copper or of crockery ware. A number
of patented sinks have an iron receptacle

for grease immediately below and at-
tached to them. It is doubtful whether
these tanks under sinks can be made of
sufficient size, without becoming clumsy,
to allow the grease to cool and congeal.
Unless properly attended to — and the
kitchen sink is liable not to be kept per-
fectly clean by the servants — grease
traps inside of a house constitute, in my
opinion, cesspools on a small scale, hold-
ing fatty waste matters which readily
become putrid and offensive. If there is
no convenient place for an outside grease
trap, better use none at all and trust to
the action of the alkalies to "cut" the
grease in the pipes. A valuable cleansing
agent for pipes, where the use of a grease
trap is omitted, may be found in occa-
sional flushing with hot solutions of
common washing soda, or better, of pot-
ash.

SLOP SINKS AND SLOP HOPPERS.

We have hitherto considered only those
fixtures which receive foul water un-
mixed with discharges from the human
system. Slop sinks and slop hoppers, as
well as water closets and urinals, in-
tended to convey to the drain these foul
discharges, are more liable to become
filthy outside and inside, unless carefully
attended to.

Slop hoppers are provided on bed-
room floors to enable servants to empty
chamber slops into them. They must
be flushed, after each use, by a sufficient
quantity of clean water from a cistern,
or else at frequent intervals by auto-
matic flush-tanks, to expel the foul water
from the trap and to wash the inner
sides of the hopper bowl or sink. Con-
sidering the character of the foul water
poured into such vessels, an efficient flush
is fully as necessary for them as it is for
water closets or urinals.

Slop sinks are made either of enameled
cast-iron or of earthenware. Then? out-
let should always be provided with a
fixed strainer to prevent any obstruction
of the trap or the soil pipe by carelessly
introduced articles, such as scrubbing-
brushes, etc.

Instead of a deep sink a combination
of a sink and a hopper, such as Merry's
slop-hopper sink, is sometimes used, and,
if provided with a strainer, it will answer
very well.

An earthen bowl, with improved flush-

Lil

HOUSE DRAINAGE and s.\M'l \i;v PLUMBING.

407

ing rim, placed on to}) of an iron or lead
hopper, will make a cleanly device. The
neatest arrangement is a slop sink,
made in one piece of earthenware, en-
larged at tin1 top to a square sink, and
provided with a flushing rim and liberal
supply of hot and cold water.

Slop sinks and hoppers should be
treated in their external finish similar to
kitchen sinks and water closets. Air
and light should tind easy access to
them: there should he no tight wood-
work around the apparatus with the
usual amount of dust and untidiness.
The floor may be of white tiles or of ce-
ment, and the walls may be laid with
tiles or with enameled bricks.

If water closets without movable parts
(hopper and washout closets) are fitted
up without woodwork (except the seat)
they may also serve the purpose of a slop
sink, provided that the flush is not for-
gotten after emptying slops. The prac-
tice of using pan, valve or plunger
closets, to get rid of chamber slops, is
decidedly objectionable. These closets
are most always encased in woodwork,
which becomes impregnated with the foul
water, carelessly emptied and often
spilled. In the case of valve closets,
the overflow pipe from the bowl is fouled
and the same is true for plunger cham-
ber and overflow of plunger closets.

URINALS.

No fixture is so liable to become un-
clean and foul smelling as a urinal, owing
to the rapid decomposition of the urine.
A small amount of urine spattered over

ipt to become quite offensive. Urin-
als, therefore, require a very liberal
amount of flushing water, running either
in a constant stream, or else delivered
automatically through flush tanks at fre-
quent intervals. The material for urin-
als should be non-absorbent and non-
corrosive.

Swinging and lipped urinals have been
much used in modern private residences,
but I should certainly advise doing away
with them entirely, as a properly con-
structed water closet may safely take
their place.

For offices, however, and public pla
such as hotels, schools, railroad depots,
places of amusement, etc., they become a
necessity, but should be under constant
supervision of a conscientious janitor,

and should receive a thorough clean

with hot water and soap, at hast ohOfl
week, and preferably oftener. Theveiiti

lation of* urinal apartments should also,
for reasons stated above, receive careful
attention.

Three kinds of urinals are in use,
viz.: single lipped bowls, fastened along

a wall, or in corners, and generally
known as " Bedfordshire " urinals ; urinal
troughs and round urinals.

Lipped urinal bowls arc made in
earthenware and of enameled iron : the
latter, however, cannot be recommended,
as the enamel is apt to scale off, leaving
the iron to corrode quickly. A number
of porcelain lipped urinals is frequently
placed along a wall, with board, slate or
marble partitions between them. They
are sometimes flushed by a stop- cock,
to be turned by hand, which is an un-
satisfactory device. Not only is the ojjen-
ing of the stop-cock frequently neglected,
especially in public places, but a flush
directly from the supply pipe will, in
most cases, be insufficient thoroughly to
rinse the sides of the urinal. If located
in upper stories, the pressure is at times
insufficient to fill the pipes, and air, pos-
sibly tainted and filled wjth disease-
breeding germs, may be sucked into the
supply pij)es, on opening the stop-
cock.

A much better flush can be obtained
by supplying flushing water to the urinal
from a special cistern, worked by chain
and handle. For public places, how-
ever, where urinals are mostly used, I
consider an automatic arrangement as
being much superior. This may be ac-
complished by operating the flushing cis-
tern from the door leading to the urinal; or
else a treadle- action flushing apparatus
may be used. Both arrangements are
liable to get out of order, and prefer-
able to either is a siphon tank, such as
Field's annular siphon, or Guinier's
siphon tank, and tilting tanks, such as
McFarland's tank and others.

Modified forms of the Bedfordshire
urinal have recently been manufactured
both in England and in this country,
which seem to possess many advantages
over the common forms, the bowls being
shaped so as to hold water (similar to a
wash-out closet) to a certain depth.
Such improved urinals are. for instance,
Stidder's urinal and the Armstrong

468

VAN NOSTRAND S ENGINEERING MAGAZINE.

urinal. With them the urine is immedi-
ately diluted with water, and conse-
quently it is much easier to keep the
bowl clean by frequent automatic flush-
ing.

Urinal troughs are made of wood
lined with lead, or of galvanized or en-
ameled cast iron, or else of slate.

Round urinals are adapted to out-of-
door location, in parks, etc.; they have a
large circular bowl, holding a body of
water, with a number of projectile lips
around its circumference, separated by
suitable slate partitions.

A constant stream of water should
trickle into trough or round urinals, in
order frequently to change the water in
the bowl, and to secure an immediate
and thorough dilution of the urine.

A modification of the trough urinal is
sometimes constructed as follows: The
back wall of the urinal apartment is suit-
ably prepared so as to be impervious and
non-absorbing. No material is better
than slate for this purpose. A horizontal
supply pipe is fastened to the wall
about five feet from the floor, running
from one end of the trough to the other.
It is provided with a large number of
openings, or sometimes with a water
spreader, from which the water is con-
stantly trickling down the walls. The
floor should be made equally impervious,
and should have a gutter with sufficient
fall to carry off the water mixed with
urine. The whole floor should be con-
structed sloping toward this gutter.
Suitable stands or gratings are some-
times provided at the stalls, which are
separated by marble or slate partitions.
The outlet in the gutter must be pro-
vided with a strainer to prevent ob-
structions of the trapped waste pipe at-
tached to it.

WATER CLOSETS IN GENERAL.

The most important and useful plumb-
ing fixture in a house is the water
closet.

Water closets should be in all houses
that make any pretentions towards con-
venience. That they are a vast improve
ment over the old-fashioned, offensive
privy vault in the back yard, everybody
will acknowledge. But it is equally true
that, unless of a good pattern, properly
fitted up, properly used, carefully watched
and frequently cleansed, they may be-

come not only the sources of foul smell
but also the cause of disease.

Leaving aside the question of the pol-
lution of the soil and of well waters, of
which the privy vault must sooner or
later be the cause, it is in itself a nuis-
ance and an abomination. In cold
weather and during rain storms persons
are liable not to use it when they ought
to, and trouble of the digestive organs
is sure to follow, as every physician
knows. This is especially the case with
females and with delicate children. Sick
persons and invalids may suffer severely
from exposure to the weather. Add
to this the often unbearable stench
emanating in hot weather from such
vaults, and it will be readily seen how
superior in point of convenience, health
and cleanliness an indoor water closet
is.

There are other improved devices for
receiving faecal matters, such as earth
closets, ash closets, tubs or pails, which
are far preferable to privies, and should
be recommended wherever water is
scarce ; but these do not properly be-
long to my subject, which refers only to
the " water carriage " system.

There is an endless list of water
closets, and each year increases the num-
ber of newly invented and patented
articles. It is, of course, impossible, nor
is it even desirable, that my paper should
give a complete description of all of
them. I shall limit myself to describing
the chief features of the various types of
closets, mentioning a few examples of
each type.

After reviewing the different patterns
of water closets in use we shall speak
of the general arrangement of the water
closet apartment with respect to light
and air.

The essential points to be considered
in examining water closets are : the
shape of the bowl or vessel receiving
faecal matter ; the apparatus for dis-
charging the contents of the bowl ; the
manner of trapping the water closet ;
the manner of flushing the bowl and
trap ; and the ventilation of the water
closet.

The less surface a water closet has
exposed to fouling, the cleaner and better
will it be. All foul discharges should
pass into water as quickly as possible.
Thus the fouling of the sides of the ves-

HOURE DRAINAGE AND samiaiiv PLUMBING.

469

will be efficiently prevented and the

water will have :i tendency to deodorize

the excrements. All water closets hold-
ing a large body of water in the howl
ve and plunger closets, wash-ont
closets and latrines) have this advantage.
In other Closets, where the body of water

in the trap (hoppers), this Latter

should he as near as possible to the

bowl ishort hoppers are preferable on

this account), and the reai- side of the

9Sel should be designed nearly vertical
and straight to prevent foul matter from

ling the bowl before passing into water.

A further requirement is durability

I simplicity <>f the working apparatus.

Tic QOving parts a water closet has

the better will it be. We must have re-

rd to the rough usage to which such
tixture nietiines subjected, especi-

ally in public places. Complicated or
delicate mechanisms frequently get out
of order, or fail to work properly under
children's or servants' hands. Nobody
will deny that, so far as this point is con-
ned, hopper and wash-out closets are

Btly superior to pan, valve and plunger

Each water closet should be separated
from the drain or soil pipe by an
it trap, placed either above or be-
low the floor, and protected, whenever
necessary, against siphonage. I consider
■ good trap as entirely sufficient, and
uot have much faith in the additional

iter seal afforded by the water in the
pan of a pan closet, or the wrater in the
bowl of a valve or plunger closet. The

pper pan quickly corrodes through the
action of sewer gas in the container,
and the flap valve gets leaky in time,
while with plunger closets flushed from
in tin; bowl may lose its water if
the outlet is imperfectly closed, as may
happen, when paper remains clinging to
the seat of the plunger. Wash-out
closets ire sometimes provided with a
double trap, which is an obstacle to a
proper flushing, and which may ac-
cumulate tilth in the hidden and mostly
unventilated space between both traps
I consider a double trap as unne<
here as on the main house drain. Wash-
out closets, the basin of which is shaped
so as to form an efficient trap, and short
hopper closets with trap above the floor,
should not have a second trap (of either
iron or lead) underneath.

The OOntentt of 0 lOBSt trap

should he thoroughly changed at each
tfu olosetj which can be accom-
plished by an efficient and liberal tlnsh.
This leads us to consider the supply of
water to such apparatus.

A water closet should have a OOfioUS
Supply i^ water completely to wash at
each use the bowl and trap as well as
all surfaces coming in contact with foul
matter. I do not, however, wish to be
understood as favoring reckHeSS irast<\ f<u
it is well known that allowing the wai
to run continuously through a wat
closet cannot be regarded as flushing.

Two or three gallons properly applied
at each use will cleanse a water closet
more thoroughly than an uninterruped
trickling flow of water. In order to be
efficient the flushing water should come
down uin a sudden dash.v To make the
flush effective the supply pipe from cis-
tern to bowl should be of large diameter,
never less than one inch, and increasing
up to 1£ inches as the head (or height
of bottom of cistern over the bowl) di-
minishes. The force of the flush largely
depends upon the shape of the bowl and
upon the head of water available in each
case. With closet bowls, circular in
shape, a flush introduced in the direction
of the tangent wrill whirl around its cir-
cumference, losing its force without
effecting much cleansing. An oval bowl
provided with a fan flush is a vast im-
provement. The best bowls are those
provided around the upper edge with a
proper ""flushing rim" into which the
water from the supj)ly pipe enters simul-
taneously at all sides, and is directed
to rush vertically downward, thoroughly
washing the sides of the closet and rel
taming sufficient force to expel the fou-
' contents of the water-closet trap.

The mode of flushing a water closet
from the main supply pipe of the house
is decidedly objectionable, especially with
closets located in upper stories of citj
houses. If water is drawn from a faucet
in the basement the pressure is often re-
duced so much as to create a slight vac-
uum in the upper part of the pipe. If the
valve of a water closet happens to be
opened at such times, air, if not foul mat-
ter, rushes into the pipe from the bowl.
Thus the purity of the drinking water is
endangered, while the closet remains
I without a flush. This risk can be j

470

VAN nostrand's engineering magazine.

tially avoided by the use of a check valve
on the supply pipe to the closet valve.
Such check valves, however, are not relia-
ble and often fail to shut properly.

Water closets should be flushed from
cisterns, never directly from the main
supply pipe. But cisterns intended for
storage of water to be drawn for drink-
ing and cooking purposes should not be
used for flushing water closets. In all
cases the use of a special cistern for each
closet or for a group of closets is recom-
mended. Such water closet cisterns are
manufactured in great variety by almost
all water closet makers.

They are supplied with water either
from the rising main or the large tank in
the attic, by ball-cocks, made sufficiently
strong to withstand the maximum press-
ure of water. In their simplest form
cisterns have only one compartment, with
a pipe attached to their bottom, leading
to the closet, and with a valve closing
this outlet of cistern, operated by a chain
and lever. An overflow pipe is provided
to prevent accidents through leakage of
the ball-cock. Such tanks are only ad-
apted for hopper closets, and should not
be used where water is scarce, as with
them a large waste is likely to occur.

Closets, holding water in the bowl
(pan, valve, plunger and washout closets)
require an "after flush" to refill the bowl,
and the cisterns should be provided for
such purpose, with a service box, holding
a certain quantity of water. The outlet
from cistern to service-box must be closed
by a large sized valve in order to secure
a quick filling of service-box.

Cisterns, arranged with a view to pre-
vent the waste of water, are desirable
wherever the water supply is apt to be-
come scanty during the hottest and cold-
est months of the year. They have, in
this case, three compartments, a large
tank, supplied by a ball-cock, a measur-
ing cistern, holding the quantity of water
fixed for each flush, and a service-box for
the after flush.

Water waste preventers for hoppers,
however, require only two compartments,
the receiving tank and the measuring cis-
tern.

Water closet cisterns are operated
either by the common pull-up arrange-
ment, a handle being connected to one
end of a lever, the fulcrum of which is
firmly secured to the floor, while the

other end of the lever is connected by a
brass safety chain to the lever operating
the cistern valve. Such an arrangement
is common for pan, valve and plunger
closets. Or else the lever and valve is
operated directly by a chain, with tassel
or ebony handle, which arrangement
seems best adapted to hoppers and wash-
out closets (and slop sinks).

An automatic " seat arrangement," in
other words, the operating of the cistern
by a depression of the seat through the
weight of the person seems most suitable
for public places, schools, factories, &c,
where people using the closet are apt to
forget to attend to the flushing. With the
seat arrangement cisterns with double
compartments and double valves must
be used. A service- box is attached to
the cistern for closets requiring an after
flush. The depression of the water closet
seat opens the valve from cistern to
measuring box, which quickly fills up ; re-
lieving the seat of its weight causes the
valve to close, and the outlet of measur-
ing box to be opened, allowing the con-
tents of the latter to rush into the water
closet bowl. As the valve closing the
outlet of the measuring box is of large
size (generally 4 inches) the water rushes
into the service box quicker than it passes
out through the 1^ or 1J inch supply
pipe, thus securing to the bowl the after
wash.

The annoyance frequently caused by
the leakage of such cistern valves has led
to the invention of other forms of water
closet cisterns. Many of these are made
to empty by siphons, such as Bean's
flushing cistern, Purnell's patent siphon
water waste preventer, Emanuel's double
siphon water waste preventer, Braith-
waite's siphon cistern, Brazier's cistern
and others.

Bean's flushing cistern, lately intro-
duced into this country, is very simple
and efficient in its action. It contains an
annular siphon, very much like Rogers
Field's siphon. The inner limb (usually
of cast iron) is firmly fastened in the cen-
ter of the cistern, passing through its
bottom, where it is connected with the
supply pipe to the closet bowl. The
outer limb, made of copper, with a dome
head, allows of a vertical movement arouu d
the inner limb, this movement being ef-
fected by a lever, working in a slot, one
end of which is. attached to the outer

HOUSE DRAINAGE \M> 8ANITAR? PLUMBING,

171

liml> of siphon, while the other carries at
end a counterweight A chain is at
bached to that extreme end of the lever
holding the siphon, and the cistern is
Operated by a handle attached to the
chain. By suddenly polling downward

the copper limb of siphon, water is forced
over the top of inner limb and the siphon
started at once. The outer limb is held
down by the suction until all water is dis-

ed, when the counterweight briu
the siphon into its original position.

The tank is supplied with water by a
hall-cock, rising with the water; the in-
ner limb - us overflow pipe unci ren-
ders a special pipe for that purpose un-
necessary.

Bean's tank provided with an 1J to 1^
inch pipe to howl is well adapted to flush
earthenware flushing rim hoppers and
slop sinks.

The double-siphon water waste pre-
venter of Emanuel, London, is a cistern
having two compartments, and a siphon
of bent pipe, the shorter end of which
opens near the bottom of the first com-
partment, while its large limb is carried
to the closet bowl. The other compart-
ment contains a smaller siphon pipe, the
shorter limb of which opens into it, while
the long limb is connected to the longer
limb of the large siphon. Both siphons
are started by forcing down a disc in the
first named compartment connected to
the lever, operated by chain and handle.
This action forces water into the larger
siphon, which quickly discharges the
water contained in one compartment
the while second siphon delivers as an
" after flush " the water of the other com-
partment.

Purnell s water waste preventer is a
plain cistern, provided with a common
siphon pipe, the longer limb of which
passes through the bottom of cistern and
leads to the water closet bowl. Neai the
bottom of cistern a branch pipe leads in-
to the longer limb, reaching to within a
few inches from the level of water in the
cistern, where it is closed by a valve.
This valve is attached to one end of a
lever, the other end of which is operated
by a chain with handle attached. To
flush the closet, the chain is pulled, open-
ing the valve, and thus water flows through
the connection pipe into the longer limb
of siphon, causing a partial vacuum,
which starts its action. The siphon con-

tinues to discharge until the contents of

cistern are withdrawn, when it completely
breaks. This cistern and Bean's d<> not

give (in their usual shape) an after tlnsh,
and are Consequently only suitable for
hopper closets, slop sinks or urinals.
Bean's tank, however, can be modified

to give this after wash, where desired.

Among automatic arrangements for

flushing water closets I mention tlnsh
tanks, working on the principle of the
siphon, o? tanks working by gravity.
They are useful in railroad depots,

schools, large factories, places of anm
ment, and in exposed localities, wh'
Standing water would be apt to freeze.
Such tanks collect a continuous driblet
from the supply cock until tilled, their
capacity being proportioned to the num-
ber of closets, and then discharge the full
contents at once into the bowl (see chap-
ter on flushing appliances).

The question of ventilation of water
closets will be referred to later in speak-
ing of the general arrangement of water
closet apartments.

. i properly trapped water closet, pro-
vided with a good flush from a special
cistern, with a flushing-rim bowl of
improved shape, located in a well ven-
tilated apartment, judiciously used and
well taken care of, should be inoffensive
to sight or smell.

Bearing in mind the general princi-
ples just stated, we wTill now examine
the various types of water closets.
There are six distinct classes viz. : pan
closets, valve closets, plunger closets,
hopper closets, washout closets and trough
closets {latrines).

These types are illustrated in Fig. 4
and Fig. 5. The closets shown, however,
are not intended to illustrate any manu-
facturer's special make ; they merely rep-
resent the various types of closets.

A shows the pan closet, flushed by a
valve, supplied directly from the rising
main, its bowl being closed by a pan,
held in place by the counterweight, the
closet outlet being trapped by a large D-
trap under the floor.

B is an illustration of a valve closet,
with cistern flush, the bowl having im-
proved flushing rim and a special trapped
overflow pipe, and being closed by a flap
valve held in place by the counterweight ;
the container is provided with an escape
pipe for foul gases, and the S-trap under

472

VAST NOSTEANDS ENGINEERING MAGAZINE.

the floor has a vent pipe attached to pre-
vent the loss of its water by siphonage.

C is a plunger closet with improved
flushing rim bowl, supplied with water
from a cistern, the outlet of the closet

by more or less complicated machinery,
the three following types are free from
any movable parts.

D is a long flushing rim hopper having
an S-trap under the floor.

being on one side and closed by a plunger
working in a chamber and to be operated
by knob and pull. The trap is above
the floor and provided with a hub to at-
tach a vent pipe.

While these three closets are operated

E is a short flushing rim hopper with
S-trap above the floor.

F is a washout closet, holding water
in the basin, which also serves as a trap.

Fig. 5 shows the general characteristics
of a trough closet (latrine).

B0U8E DB S 1 \ LGE \N l> - \M T \\:\ I'll M BING.

PAN 0LO8BTS.

To this class of closetfl belong the
Philadelphia valve closet, the Bartholo-
set, Harrison's u Empire "
. Oarr'fl M Monitor" closet, the
beth pan closet, Dnderhay's pan
t. Banner's closet, Craigie's "
cka " closet, Craigie's ''Century-' o
and many others.

The name 'waive'" closet is an improp-
er one. and leads to confounding these

with those ^( the second type

: name is derived from the usual

air fr«»m the container. The contents

of the howl or pan are discharged by
tilting the pan by means of a lever,
while a flush is simultaneously started.

This pan works in an iron receiver or
"container," upon which (he howl is
usually fastened with putty. The outlet

of the r is trapped by the com-

mon S-trap, although it is not uncommon

to find in old houses a D-trap under the

water closet, a second "container" of

foul matters. The foulest part of the
pan closet is the receiver, for the soli, Is
gradually aecumulate on its sides, as

Fig.5

UUJ4T — H4J4U-t

Latrine

manner of supplying the flushing water
to the closet, by joining the supply pipe
to a more or less slow shutting valve,
worked by the pull or handle of the
closet. These valves are mostly unrelia-
ble, wear out and leak, especially when
subjected to varying pressure from the
street main. Pan closets may, however,
be flushed by a special cistern with lever
arrangement, and therefore the above
serious defect is not one characteristic
to these kind of closets.

The real defects of the pan closets
will be at once apparent by inspection
of Fig. 4. A. The excrements are re-
ceived in a bowl, closed at the bottom
by a copper pan, holding a few inches
of water and forming a seal against the
Vol. XXVH.— No. 6—33.

these receive no washing from the flush.
The filth soon undergoes decomj^osition,
and the resulting gases, having been
confined by the double water-seal of.the
pan and the trap, are expelled into the
apartment at each use of the closet. They
also frequently find an exit at the hole,
through which the spindle, tilting the
pan, passes. And finally, the putty joint
between bowl and receiver may become
untight and afford means for the passage
of sewer gas. The flush is insufficient in
most pan closets to clean the bowl ; it
certainly loses all its force before reach-
ing the container, foulness accumulates
here and excremental matter lodges in the
trap, as the flush is not strong enough to
drive it out through the dip or water-

474

VAN NOSTRAND's ENGINEERING MAGAZINE.

Some of the enumerated defects may
be obviated by enameling the inside of
the cast iron receiver ; by ventilating it
by an inlet pipe for fresh air and a vent
pipe ; by having special flushing arrange-
ments for the container ; by using a bowl
with an improved flushing rim or ,a fan
spray, the water for the flush being de-
rived from a special tank. But by all
these costly improvements the only merit
of the pan closet, its cheapness, is annihi-
lated, and a better water closet may as
well be used. As long as a house is fit-
ted with pan closets, of whatever pattern,
it may be said not to have reached the
standard of safety from a sanitary point
of view.

VALVE CLOSETS.

To this class belong the following
water closets : The old " Brahmah "
closet, Hellyer's improved valve closet,
the Lambeth valve closet, Tyler & Sons'
patent valve closet, Underhay's valve
closet, Bolding's " Simple " valve closet,
Carr's American " Defiance " closet,
Mott's " Climax " closet, Mott's " Whirl-
pool " closet, Demarest's "Acme" closet,
the Alexander water closet, the " Vic-
tor " sanitary valve closet, the Lambeth
trapless closet, Tylor & Sons' trapless
closet, Bean's valve closet and others.

The valve closets (Fig. 4. B) are cer-
tainly a vast improvement upon the pan
closet. Instead of being closed by a
pan, the bottom of the bowl is closed by
a flap-valve, from which the closet takes
its name. This valve is tightly held in
place by a counterweight on a lever to
which the pull is attached. By lifting
the pull, the valve, which is hinged, is
turned downward, and allows the con-
tents of the bowl to drop into the trap.
The container is much smaller than in
the case of pan closets. It generally has
a ventilating pipe to remove foul gases.
The bowl holds a large quantity of water
into which the solids are dropped and
instantly deodorized. It is provided
with some of the best closets of this
type, with a superior flushing rim, and is
flushed by a special cistern. As the flap
closes tightly against the bottom of the
bowl this must be provided with an over-
flow which should have a trapped con-
nection to the container. Unless some
water is furnished to this trap at each
flush it is liable to lose its seal by

evaporation, thus establishing a direct
connection between the container and
the atmosphere of the water closet
apartment. Such driblet to the trap of
the overflow is supplied at each flush in
the better valve closets. There is some
danger of the fouling of the container.
To prevent this the better closets have
the inside of the container enameled, and
as a larger body of water rushes from
the bowl through the container at each
discharge, the danger is much less than
with the pan closet.

If such closets are flushed from a valve
the solids will be driven out of the lead
trap only after repeated flushing Better
closets of this class have suitably arranged
cisterns, which deliver quickly a large
body of water to bowls with improved
flushing rims, and thus the danger from
foul matter being retained in the trap is
much reduced. After continued use the
flap-valve is liable to leak ; excrements or
paper may stick to it and prevent its
tight closing, and all water will leak out
of the bowl. Thus the additional water-
seal is lost and the bowl is more liable to
become fouled.

The Lambeth and Tylor's trapless
closets are different from those just de-
scribed. The outlet of their bowl is
placed at the side, not at the bottom, and
is closed by a vertical flap valve hinged to
spindle and lever, and held in place by a
counterweight.

Such valves may be less liable to be
fouled with solid matters and may close
more tightly on this account. The water
rushing out of the bowl in a .large body
will effectually flush the outlet of closet.

Both closets do away with the trap and
rely for exclusion of sewer gas only upon
the flap-valve and the water in the bowl.
In speaking of traps under fixtures I have
already stated that each fixture should
have a trap, and I would much prefer dis-
pensing with the additional water-seal in
the bowl than with the trap under-
neath the closet. Such, trapless closets
are not safe, for should the mechanism of
the flap -valve get out of order the house
would be entirely open to the invasion of
sewer gas from the soil pipes.

PLUNGER CLOSETS.

Among closets of this type I mention
Jenning's closets, the Demarest closet
Mott's "Hygieia" closet, Moore's closet'

BOUSE DRAINAGE AM) SAN IT ART PUMBING.

475

Zane's " Sanitary '* closet, the California
"Perfection *' closet, Myer's Gale closet,
Myer's China closet, the Hartford Glass
closet, Myer's egg oval water closet,
Smith's "Arizona1 plug water closet,
Pearson's Twin basin closet, Smeaton'a
trapless water closet, Smeaton's "Eddy-
stone " closet and oth(
The characteristic detail of all these
Fig. 4 0) is the plunger closing the

outlet of the bowl, which is placed at the

side of the closet The foul matters drop

into a large body of water in the bowl,
are therefore partly deodorized and easily
removed from the bowl. By lifting the
plunger the contents of the bowl are ra-
pidly discharged into the soil pipe, and
the rush of the water, leaving the bowl,
is so great as effectually to drive all
matters through the dip of the trap.
The latter must be efficiently protected
against siphonage, which is more likely to
occur with plunger closets than with the
pan, valve, or hopper closets. The dan-
ger with closets of this class lies in the
fouling of the plunger chamber. Waste
matters and paper may stick to the
seat of the plunger or to its sides ; the
outlet will then be imperfectly closed,
allowing the water to leak out of the bowl.
Closets having a small plunger chamber
are the better ones, not only because they
will be cleaner, but because with large
chambers the waste of water must neces-
sarily be large.

Plunger closets flushed by a special
cistern require no supply valve nor float
in the plunger chamber, which, therefore,
may be of smaller dimensions, and hence
are superior to other closets of this type.

In some plunger closets a special spray
arrangement is intended to wash the sides
of the plunger and its chamber at each
use of the closet, but, while it may be ef-
ficient, it tends to complicate the closet.
The better closets of this class provide
the top of the bowd with an improved
flushing rim, or wash the sides of the
bowl by an effective fan or water-spreader.
In order to provide for an overflow the
plunger is sometimes made hollow, and
when trapped it is so arranged that the
water forming a seal is renewed at each
flush. Otherwise it is liable to evapo-
rate and this is especially dangerous
with plunger closets that are trapless.

Trapless plunger closets are not safe

for same reasons as stated for trapless

valve closets.

In some closets an independent over-
flow is arranged. .Most plunger closets
are flushed by a valve, worked by a float
in the plunger chamber. These valves
are not always reliable, especially under
varying pressures, and it is much better
to flush these closets from a special cis-
tern.

HOPrEIl CL0SET8.

There are many varieties of hoppers.
made in iron or in earthenware. The
latter are much preferable, and the for-
mer should never be used unless well
enameled inside. Among the best hop-
pers I mention Hellyer's long and short
"Artisan" hoppers, Myer's "Niagara"
hopper, Demarest's long and short earth-
en hoppers, Hubers' long and short
earthen hoppers, Rhoads' hopper, Ivers'
hopper, Harrison's drip tray bowl flush-
ing rim hopper, the Lambeth " Cottage "
closet, Smith's " Odorless " hopper, Hen-
derson's Automatic water closet, Mad-
dock's hopper, Moore's " perfectly odor-
less " sanitary closet, Watson's hopper
and others.

Hoppers (Figs. 4, D & E) are sometimes
liable to become soiled at the sides of
the bowl, and for this reason have not
become favorites with many. The hopper
lacks the advantage of the pan, valve and
plunger closets, in which the excrements
drop immediately into a more or less
large body of water, and thus carried in
suspension by the water, are easily re-
moved from the bowl by tilting the pan
or valve, or by lifting the plunger. A
good practice is to wet the sides of the
hopper before use, and where the hopper
is flushed by a special cistern such a de-
vice has been arranged to work automat-
ically. The rear part of a hopper should
be vertical and straight, so that matters
will drop immediately into the water of
the trap without touching the sides of
the hopper. The inside of hoppers should
be very smooth, and for this reason,
earthenware is much preferred to enam-
eled iron, because the enamel scales off
gradually. In order to have as little
surface as possible exposed to fouling
the sides of the hopper should be short,
which is in some accomplished by hav-
ing the trap above the floor. The ap-

476

van nostrand's engineering magazine.

parent greater cleanliness of the pan,
valve or plunger closets is simply a de-
lusion. It is true, the hopper will
sometimes have its sides soiled with ex-
crementitious matter, when the supply
or the manner of flush is inadequate.
But the defect is in sight ; it shows it-
self to the person using or in care of the
closet, and it can easily be remedied by
proper occasional application of hot wa-
ter, soap and a scrubbing brush.

Not so with the other closets. The
dirty matter may be out of sight, but it
often remains hidden in those parts of
the closet which are not easily accessible,
and therefore never cleaned or inspected,
until a leakage occurs, or until some foul
odor compels the householder to call for
the plumber.

The great merit of hoppers lies in their
simplicity and in the total absence of any
mechanical parts which, sooner or later,
fail to work properly, especially when the
closet is carelessly used. Much depends
with a hopper closet upon the manner of
flush. The practice of turning a stopcock
and thus introducing a feeble stream into
the hopper, which whirls around its in-
side, is objectionable. Hopper closets
should always be provided with flushing
cisterns allowing a bountiful supply to
rush vertically downward through a large
supply pipe and a well-shaped flushing
rim.

Rhoads' porcelain seated hopper is a
cleanly device for hospitals, schools, fac-
tories, railroad depots, public buildings'
&c, provided it is well flushed, and only
where the apartment can be well heated
in winter, as otherwise, the seat being
cold, the closet is liable to be improperly
used.

Hoppers with wooden rims for a seat,
attached to the bowl will answer better
than Rhoads' hopper in exposed places,
the only objection being the possible ab-
sorption of urine through the wood.

WASHOUT CLOSETS.

I have grouped a number of recently
invented water closets into this last class
which I consider, in principle, far supe-
rior to any of the other closets for the
following reasons: They are mostly
made in one single piece of earthenware
and are entirely free from any movable
parts (see Fig. 4, F). Moreover, the
bowl of many closets of this type is shaped

in such a manner that its outlet or over-
flow forms a very efficient water-seal trap,
thus obviating the necessity of a trap un-
der the closet. All washout closets have
their basin so shaped as to hold a large
quantity of water; the advantages of
such an arrangement have been already
stated. A washout closet is in fact oniy
a modified and improved form of hopper.

In England closets of the " washout "
type are preferred of late to other closets,
and in this country quite a number
of such closets have been introduced.
Among closets of the washout type I
mention: The "National" side outlet
closet, Owen's closet, the Lambeth "Flush-
out " closet, Carmichael's " Washdown "
closet, Woodward's "Washout" closet,
Bostel's " Brighton Excelsior " closet,
Dodd's Patent closet, Hellyer's "Vortex"
closet, the " California " or Smith's " Si-
phon Jet " closet, the " Dececo" closet,
the " Tidal Wave " closet, and others.

Different means are employed with the
closets of this class to effect a discharge
of the bowl. In many the downward
rush of water directed through proper
flushing rims so as to concentrate its
main force at the outlet of the basin,
drives the contents of the bowl into the
overflow, and thus into the soil pipe
(" Brighton " and " Vortex " closets). In
others a jet of water is introduced into the
outlet pipe and carries all water from the
bowl, partly by the force of the jet, and
partly by starting a siphoning action
(Smith's "Siphon Jet" closet). Instill
others a partial vacuum is created by
different means in the outlet and a true
siphonage established (" Dececo " and
"Tidal Wave" closets).

LATKINES.

Latrines and trough water closets are
frequently used in public places, schools,
railroad stations, factories, hospitals,
military barracks, etc. Latrines (Fig. 5)
consist of a series of strong stoneware or
cast iron porcelain lined pans connected
with each other by a suitable vitrified or
cast iron pipe at the bottom of the pan
or bowl, and forming one piece with it.
At the end of the last section a discharge
valve is placed, being an upright pipe in
which a plunger works, the latter being
hollow so as to serve also as an over-
flow. As the plunger closes the outlet
tightly, water is held back in the latrines

BOUSE DRAINAGE AND v\\ii.\i:v PLUMBIB

477

to the height of the overflow in the
plunger. The plunger or discharge
valve is under control of a janitor, who

raises this ping as often as found nee
ry to empty and clean the latrines.

The water then rushes out of all the
bowls with great force and in great
quantity and everything is effectually

carried out oi the plunger chamber and
trap underneath. Moreover, each bowl
is provided with a supply pipe to rinse
its sid h time the ping1 is raised.

soon as the plug is dropped, the bowls
and connecting pipes till with water and
are, in a few moments, again ready for
use. The bowls are generally formed so
that no excremental matter can strike
their everything drops at once

int r and is partly deodorized.

The only part which may get foul in
time is the plunger chamber, although
this is not as likely to occur with latrines
as with a single plunger closet.

Trough water closets are constructed
in different manners, generally of brick-
work with vertical side walls and round
bottom, but sometimes of iron, holding
a large quantity of water, with the bot-
tom of trough inclined to the end,
where the discharge plug is situated,
and with a single or double row of seats
placed above them. They are somewhat
expensive than latrines, and fulfil,
in some cases, a good purpose.

A good substitute for latrines and
trough closets may be found in a num-
ber of flushing rim all earthen hoppers,
such as Rhoads', Hellyers', Demarest's or
the Niagara Hopper, with wooden rim j
attached to the bowl as a seat, each
provided with a trap and flushed auto-
matically either by Field's annular siphon |
tank or McFarland's tilting tank, as often
as desired, the operation of emptying !
and flushing the closet being thus made |
entirely independent of the carelessness
or forgetfulness of the persons using the
closet.

GENERAL ARRANGEMENT OF WATER CLOSET
APARTMENTS.

In speaking of plumbing fixtures in
general I have decidedly condemned the
usual manner of encasing fixtures with
tight woodwork. While this is objec-
tionable with any kind of plumbing ap-
paratus, it is even more so with water

closets. With a tightly boxed-up water
closet ventilation is impossible under the

seat ; the frequent cleaning of the ap-
paratus is neglected, the lloor often be-
comes wetted with mine drippings or
water spilled in Carelessly using the
closet as a receptacle for slope; the filthy
liquid soaks into the absorbent lloor,
which constantly remains damp and
emits unpleasant odors into the apart-
ment.

As an abundant supply of water is
most essential to the interior of the bowl
and closet, so is plenty of light and air
indispensable to the outside of the
closet. A water closet should stand free
on the floor, readily accessible on all
sides. The only woodwork necessary is
the seat ; this should be without a cover
and can be hinged and leaned against
the rear or side wall, when the closet is
not in use. Such an arrangement looks
especially neat where the floor is laid in
tiles, and if the water closet is entirely
of white crockery ware, for instance a
long or short flushing rim hopper, or an
earthenware wash-out closet.

Col. Geo. E. Waring, Jr., thus de-
scribes such an arrangement : a closet,
" made of white earthenware, and stand-
ing as a white vase in a floor of white
tiles, the back and sidewalls being sim-
ilarly tiled, there being no mechanism of
any kind under the seat, is not only
most cleanly and attractive in appear-
ance, but entirely open to inspection and
ventilation. The seat for this closet is
simply a well-finished hardwood board,
resting on cleats a little higher than the
top of the vase, and hinged so that it
may be conveniently turned up, exposing
the closet for thorough cleansing, or for
use as a urinal or slop hopper. Such
closets ought entirely to do away with
the use of urinals in private houses, and
if, for convenience or to prevent the pos-
sibility of baths being improperly used,
separate slop sinks are desired, these
should be constructed like the hopper
closet, the outlet being protected with a
movable basket of wire cloth made for
the purpose."

The arrangement suggested adds, of
course, to the expense of a water closet,
but, where white Minton tiles should
prove too costly, a plain cement floor, or
slate, or else enameled tin may be sub-
stituted for them. A tight hardwood

478

VAIN" NOSTEAND'S ENGINEERING MAGAZINE.

floor is well suitable, and may be cov-
ered, if desired, by oilcloth.

"Wherever woodwork is used for the
sake of better appearance of closets hav-
ing- mechanical parts (plunger closets,
valve closets), at least the riser should be
arranged with lattice work or a great
number of perforated holes to provide
ventilation under the seat.

It is desirable to locate water closets
near an outer wall, in order to give the
apartment ample light, and a window
opening on the exterior of the house, for
ventilation. Where such an arrange -
,raent cannot be secured — andit is seldom
possible to do so in American city dwell-
ings— the apartment should have bor-
rowed light and special means for its
ventilation should be provided. A dark,
unventilated, narrow space for a water
closet, opening into a dressing room, or
situated off a staircase landing, or even
close to sitting rooms, is an abomination.
In England water closets are "con-
structed inside a house with an inter-
mediate vestibule, with a cross-current
of air, so as to cut off the air in the
house from that in the closet." The
rigor of the climate in our Northern
States forbids such an arrangement,
but in moderate climates it is quite
practicable to locate water closet and
slop sink apartments in a tower con-
nected to the main building by a pass-
age or hall, which, however, is separated
from it by double doors, the hall being
efficiently ventilated by two windows on
opposite sides. If located in the center
of the house such apartments need
sometimes artificial lighting by gas, in
which case the heat of the gas flame can
be utilized to create a constant draft and
thus to ventilate the closet apartment by
means of tin or galvanized iron pipes,
extended — independently for each apart-
ment— through the roof. Fresh air
should, in such a case, be supplied to
the room, either by blinds in the door,
or else by cutting away its lower two or
three inches.

Sometimes in order to remove noxious
gases generated in using the closet, a
special vent pipe is attached to the
closet bowl, leading into a constantly
heated flue, used for this purpose only;
or else an upward draft is created in the
vent pipe by connecting it with a cham-
ber, in which a gas jet is burning, and

the outlet pipe of which enters the flue,
or extends up to the roof. Such a vent-
ing of the closet bowl is provided, for
instance, in the Zane plunger closet, in
E. D. O. Smith's " Odorless Hopper
Closet," in the "Worcester Hopper,"
Maddock's "Inodorous" Hopper, Moore's
"Sanitary" Water Closet, Huber's hopper,
with vent pipe attached to bowl, Wat-
son's hopper, Mott's ventilated hopper,
Harrison drip tray bowl hopper, and
others.

Sometimes such a ventilation is ap-
plied directly under the seat, by using
an annular flat zinc tube, provided with
a number of openings at the inner edge,
and connected to a special flue.

It would be a serious mistake to run
such vent pipes into a kitchen flue, and
far more so to run them into any other
chimney of a building. There is at times
a downward draft in these — even in the
kitchen flue, the fire of which may go
out over night — and thus offensive gases
from the closet would be carried into
the house. Another reason against such
a course is that small vent pipes would
soon become obstructed by soot. The
best course, where a special flue has not
been arranged, is to run the vent pipes
along some heated flue up to the roof,
and terminate their ends at a point
where they are well exposed to the cur-
rents of air. These remarks apply also
to the vent pipes of containers of pan or
valve closets.

It would almost seem superfluous to
state that vent pipes from closet bowls
should never enter a soil or waste pipe,
or a vent pipe from traps. But such
cases are not rare, and an instance of
such pernicious practice — which should
be considered either as criminal careless-
ness or else as utter stupidity and in-
ability of the mechanic — was related to
me only a short while ago.

While speaking of the proposed use
of kitchen flues for vent pipes of
closet bowls or containers, I might men-
tion the fact that it has repeatedly been
proposed to utilize the heat of the kitchen
chimney for the ventilation of soil pipes,
by running these from above the highest
fixtures into such heated flue. Such
practice is not permissible under any
circumstances whatever, for there are at
times downdrafts, which would force soil
pipe air into the house. Besides this, it

HOUSE DRAINAGE AND 8ANITABY PLIMBTNG.

479

is well known that bricks absorb gases,

and would thus in time become impreg-
nated with Bewer gas.

For public places, such as railroad
depots, schools, colleges, hotels,
where water closets are likely to be used
in rapid sti D at certain times of

the day. a special : ruilation of the apart

/it is necessary, even where windows
are provided, to remove offensive smells
from the use of the closets, which may
arise, however well the closets may be
trapped and the pipes ventilated. It
would lead too far to consider in detail
the best means for ventilating such apart-
ments. Suffice it to say, that providing
only an exit for the foul gases cannot be
regarded as ventilation. To preserve
the purity of the atmosphere in such
apartments it is necessary to introduce
a sufficient quantity of pure air, moder-

ly heated in winter time, and to pro-
vide an outlet for the foul air. A much
disputed question in locating this outlet
is whether it should be near the floor
or near the ceiling. The former may
have advantages from an economical
point of view, but from a sanitary point
of view, which should only be taken into
consideration in the ventilation of such
apartments, I should always advise locat-
ing the outlet near the ceiling of the
room.

No amount of ventilation, however,
will keep the air of the apartment pure
unless the water closet is frequently
and thoroughly washed aud scrubbed.
Such cleansing is much facilitated with
the above suggested arrangement of a
water closet.

The following valuable remarks of Mr.
Edward S. Philbrick upon this subject
so fully express my own views, that I
quote them in extenso : "The location
of plumbing fixtures in dark corners,
under stairways and in closed closets is
always to be avoided. Such fixtures,
even if of the best materials and design,
need frequent washing and even scalding
to keep them sweet, and the more light
and air can be admitted to them, the
more likely will the occupant be to en-
force such cleanliness. The best author-
ities in England recommend the location
of water closets outside the house walls,
in towers or outside appendages. The
rigor of our climate forbids such an ar-
rangement in the Northern States, but

they can often be s<» placed Dear the
out r wall of the house as to allow of a
window for the direct admission of light
and air, I. 6. in the same apartment.
This can be done in all suburban houses
without an undue sacrifice of light in
the living and sleeping rooms, though
city houses can rarely afford anything
better than skylight and vvell light for

them The water closets on

the basement floor are generally the
source of much trouble by injudicious
location and subsequent neglect. The
rareness of the inspection generally
given to such fixtures by heads of
families renders it all the more needful
to i^lace them where they ean be readily
and easily cleaned and well aired. . . -
But however good the apparatus and
however well located, nothing will com-
pensate for neglect by the occupants of
the house. Frequent applications of hot
water and soap are just as needful to
the surfaces of such fixtures as to the
bodies of the persons who use them.
Of course the woodwork about them
should be so put together as to be
readily taken apart without tools by any
house-maid, to be periodically cleaned
and aired. What is the custom in this
respect? Expensive apparatus is often
seen so boxed up by screwed and even
nailed joinery, that the spaces so en-
closed are practically inaccessible and
soon become abominably foul from spat-
teriugs. The less amount of woodwork
the better, but by all means have the
whole so as to be ready of access with-
out the need of so much as a screw-
driver, and let every house-maid be
taught the necessity of a regular rou-
tine in the cleansing operations, scald-
ing and scouring every surface which
has been exposed either to the spatter-
ing of urine, or even to the perspiration
of the body. It may not be always
possible to enforce such discipline, but
the less it is enforced, the more import-
ant become the items of light, air and
simplicity of construction, as aids in the
same direction. The latter are generally
under the control of the architect, and
his mistakes of planning entail a per-
manent and incurable evil, which it is
therefore all the more important to

avoid While every aid

should be given to cleanliness by sim-
plifying the apparatus, no amount of

480

VAN NOSTRAND's ENGINEERING MAGAZINE.

perfection in this respect will avoid the
need of constant thought and care on
the part of those who use the fixtures,
as well as those whose duty it may be to
cleanse them. Such perfections of appa-

supervision of the head of the family, but
the trouble increases in a manifold ratio
where fixtures are applied in hotels or
public places, or in tenements to be used
by more than one family."

i-<*-

a
o

•a

ratus are but aids, and though not to be
ignored by any means, are after all but
of little avail if the people who use them
are reckless and wanton in their habits.
It is difficult enough to keep such ap-
paratus in good order in private houses
where not used by any one beyond the

FLUSHING APPLIANCES.

Flushing tanks should be provided in
a system of house drainage, whenever it
is impracticable to lay the drain at an
inclination which will secure a sufficient
cleansing flow. The idea underlying

HOUSE DRAINAGE AND 8ANITARI PLUMBING,

481

most of these flushing arrangements
the accumulation of a small flow of
water — often merely a driblet— which

atinuously running, at a sluggish rate

old in»t be able to remove deposits in
the drain. Whenever this water lias ac-
cumulated to .t large volume, the flush
lutomatically emptied and its
ire driven with a sudden rush
through the drain. As this may be re-
ben as found necessary,
me :11s of the drain may be kepi

thoroughly cleansed, and any decom
f organic matter is thus effectu-
ally prevented.

Automatic flush tanks are likewise

frequently used for flushing a number

of water i . urinals or ship sinks,

single water closet, if in

d locality, where the water in

the supply pipes would be apt to freeze

unless kept constantly running. It has

ted that such continually

running driblets are unable to produce

flush, but, by collecting the

driblets in a flush tank, discharging

automatically, when tilled, the desired

purpose may easily be accomplished.

There are many varieties of flush
tanks, such as Field's siphon tank,
McFarland's tilting tank, Shone's flush
k. Magnire's, Rhoads', Hydes', Ivors',
"Wilson's. Guilder's tanks and others.
Field's flush tank, the invention of the
U-known English engineer Rogers
Field, has been used with success in
this country. One of his tanks has a
siphon, and is started only by a
iden addition of a larger quantity of
water. The other tank is provided with
an annular siphon, the outer and inner
limb being concentric. This tank is
started by a small trickling flow. It may
be constructed of small size, to flush a
row of hopper closets or urinals auto-
matically. Larger tanks are used for
flushing house drains and town sewers,
and are also adapted for sewage disposal
-ul> surface irrigation.
Fig. G, A, shows a Field's flush tank
with annular siphon, the tank being of
wood lined with sheet lead. The long
inner limb of siphon reaches into the
trapping box suspended underneath, in
which the water level is kept about one-
sixteenth of an inch below the end of inner
limb of siphon by means of the second
"auxiliary " siphon. The working of t la-

tank is as follows: A^ soon as the water
from the faucet has Ailed the tank' so that

the water rises to the top of the longer (in-
ner) limb of siphon, it commences to over-
(low, but is guided by a conical-shaped ad-
jutage to drop clear of the sides, and seals
the mouth of lower limb. In falling, the
r carries an- with it. which is thus
displaced and driven out at mouth of
inner limb in trapping box. A slight

vacuum is gradually created in the dis-
charging limb, sufficient to start the
siphon, which rapidly empties the tank'.
">n as air is admitted through outer
(shorter) limb of siphon its action is
stopped, all the water in the inner limb

drops into the water chamber, and the

auxiliary siphon lowers the water line in
trapping box about one-sixteenth of an

inch below the mouth of inner limb. Air
enters at this place and completely breaks
the siphon; the tank is then ready for an-
other discharge. The stopcock can be
regulated to fill the tank more or less
rapidly according to option.

McFarland's tank is shown in Fig. 6,
l>. It works by gravity, and is simpty a
bucket hung in a cistern, working in
brass journals. As soon as filled from a
faucet regulated to let the water in slowly
or quickly as desired, the bucket tips over
and empties the entire contents at once.
This tank is well adapted for flushing
closets, slopsinks and urinals.

I have endeavored, in these papers, to
explain what means and devices should be
used, and what rules must be followed,
speedily and safely to remove by the
water carriage system all liquid and semi-
liquid wastes from habitations. The all-
important question of bow to dispose of
the waste^ matters of the household in
the safest, hast disagreeable, most effi-
cient and most economical manner has
not been referred to.

The discharge of sewage into water-
courses or into the sea. its treatment by
chemical processes, filtration of s 'wage,
surface and sub-surface irrigation, inter-
mittent downward filtration of sew
the processes of dry removal, by pail or
tubs, earth closets, ash closet- tools,

privies, vaults, manure pits and kindred
subjects, the removal of garbage, kitchen
slops, ashes, etc., in other words. •* Tin

>osal of Household Wastes* will be
made the subject of a future paper.

482

VAN NOSTKAND'S ENGINEERING MAGAZINE.

THE MECHANICAL ENGINEER— HIS WORK AND HIS POLICY.

THE PRESIDENT'S ANNUAL ADDRESS.

Delivered before the American Society of Mechanical Engineers, at the Annual Meeting, November 2, 1882.

By ROBERT H. THURSTON, A.M., C.E., President.

introductory

Gentlemen of the Society : — Ladies and
Gentlemen :

It is with mingled feelings of pleasure
and of regret that I appear before you
for the third time to deliver the formal
opening address, at the annual meeting
of the American Society of Mechanical
Engineers.

I have to express, inadequately as I
may, my sense of the honor accorded me
and my appreciation of that kind feeling
and of that confidence which placed me
in this chair as your first President, and
to-day particularly, my gratification that,
after conferring that distinction for an-
other term, both officers and members
have so kindly and effectively upheld me
in the effort to secure«a firm and perma-
nent basis for future usefulness for this
Society.

In retiring after two and a-half years
of service, I have the proud satisfaction
of being able to look back upon an initial
period in the history of the Society which
is> perhaps, unexampled, and I gladly fall
back into the ranks of a body which al-
ready numbers 350 members, and which
includes in its list nearly every distin-
guished engineer in the country as well
as a large number of the younger and
brighter minds now coming forward to
do our work, a Society which boasts on
its list of honorary members the greatest
engineers of Europe.

In the first of my two earlier addresses,,
I attempted to lay before my audience a
concise statement of the character of this
organization, the objects proposed to be
attained in its formation and by its ac-
tion, and the principles which I con-
ceived should guide it, as a body, as well
as its members individually, in their ef-
forts to further those objects.

In my second annual address, I en-
deavored to indicate what progress had
een made, and what stage had been

reached, in the various arts which consti-
tute our department, and to show what
direction our steps are now taking and
what are the needs of the time so far as
they concern the mechanical engineer. I
pointed out what seemed to me the more
important problems presenting them-
selves for solution, and stated what were
apparently the most promising directions
in which to seek results.

I finally called attention to the relation
of technical instruction, and of systematic
training in the arts to our profession, and
urged the supreme importance of making,
promptly, the most energetic efforts to
inaugurate a general and complete
scheme of public and private education.
In this, my third address, I propose to
review very briefly the work of the me-
chanical engineer up to this date, to pre-
sent a concise summary of what has been
accomplished, and to again examine the
line of progress with a view to ascertain-
ing more exactly than before in what di-
rection our labors may be most profitably
directed in the near future. Nature
rarely turns a sharp corner in any of her
great movements, and the direction of
our progress may be expected, in the im-
mediate future, to be very nearly what it
has been in the recent past. Newton's
laws hold as well in sociology as in me-
chanics. Finally, I propose to touch upon
those great social problems which concern
the engineer even more than our fellow
citizens, not simply because he has to
deal more directly with them, as an em-
ployer and a director of labor and of
capital, but, principally, because it is his
province, his duty, his privilege, more
than that of other men, to study and to
solve them, and to inaugurate and carry
to position all those great measures to
which their solution leads.

materials.

In the handling of metal, we have still
much to learn. The weakness of the

THE MECHANICAL IN (.I.N ill:.

483

large sections of metal necessarily used in
our heavier work still remains :i serious
evil, and our inability, especially when
using steel, to Beonre the highest tenacity
of the metal is a standing reproach to our

profession. I have had ocvasion to test
hundreds, yes, thousands, of samples of
iron and steel during the last few years
and have never yet found a maker able to
d tenacity in large and small
This difficulty seems particularly

lions in dealing with forged iron built
up oi scrap and with heavy sections of
any kind of steel. I lind iron carrying
75,000 pounds per square inch in No. 8
wire, .")."). 000 in inch bars, ami falling to
40,000. or even 35,000, in heavy engine-
shafts and beam-straps. Steel varies still
more seriously. It is to be hoped that,
with the more general use of ingot metal,
the introduction of hydraulic forging,
and of improved methods of heating and
handling, so as to avoid the introduction
of many small parts in building up large
masses, or frequent exposure to high tem-
peratures in the process, this element of
cost and danger may, in a measure at
least, disappear.

The great testing machine at Watei town
Arsenal is constantly at work, under the
direction of Colonel Laidley, sometimes
for private and sometimes for public
benelit, and has already done some ex-
tremely valuable wrork in that important
and unexplored held — the investigation of
the strength of large sections and parts
of structures. Its most valuable work is
done intermittently and its usefulness is
far less than it should be and would have
been had its original purpose been ad-
hered to. There seems no immediate
prospect of the resumption of the great
work organized in 1875. and planned and
commenced by the Government Board.

The petitions of this Society, of the
Society of Civil Engineers, of the Insti-
tute of Mining Engineers, of the Iron
and Steel Association, of the faculties of
the leading technical schools and colleges
of the United States, and of business men
and other private individuals of all classes,
with all the influence that they could
command, separately or collectively, have
been inadequate to secure the restoration
of that Board, or the creation of a similar
organization, or the resumption of the
great work barely planned and begun by
the old Board.

This fact is as suggestive of the Q<
sity of a movement on the pari of the busi-
nessmen of the country for the purpose of

suring some influence in its govern*

ment, as it is remarkable as illustrating
their utter impotence to-day. Meantime,
the Ordnance Bureau of the Army has a
small appropriation for use in this direc-
tion and we shall look with hopeful in -
terest for results.

But "Iron, tough and true, the weap-
on, the tool and the engine of all civiliza-
tion," as Theodore Winthrop calls it, is
now fairly displaced by its younger rival,
limild strd," or more exactly, -t ingot" or
"homogeneous" iron.

For all shapes that can be rolled this
revolution is accomplished and, in forged
work of small size, the change is hardly
less complete. This is especially true of
railroad work, and not only rails, tires
and axles, bolts, rivets and boiler plate
are becoming common in steel, but pis-
ton and connecting rods, all forged parts
of the valve gear and minor parts of the
engine, are now made in this tougher,
stronger and more uniform and reliable
metal.

The introduction of the basic process
— tardy as it is — by cheapening the stock
of the steel maker, and the steadily increas-
familiarity of makers and users with the
characteristics of the new metal and with
the requisites for successful manufacture
of demanded grades and better qualities,
will undoubtedly, before many years,
make its use so general that puddled and
forged iron will become almost or quite
unknown in our art. The growth of
pneumatic steel manufacture in this coun-
try during the past ten years has been
most remarkable. In 1870 we were mak-
ing somewhere about 20,000 tons, in 187.'}
about 160,000 tons, and to day are turning
out one million and three quarter tons ;
while the price has fallen below that of
the finer brands of iron.

A few years ago — even those among us
whose hair has hardly begun to grey can
remember the time — no engineer except
Telford with his proposed cast-iron bridge
of 600 feet span, dared present plans of
iron truss or arched bridges of 300 feet
span ; and Roebling wTas the only engi-
neer bold enough to attempt much
greater spans, even with suspension
bridges.

To-day, with improved material and

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VAN NOSTKAND'S ENGINEEKING MAGAZINE.

the better knowledge of their quality that
comes of intelligent inspection and sys-
tematic test, we think little of trusses
of 500 feet span or suspension bridges
of 1000 feet and more ; and it is even
proposed to bridge the Forth at its
expansion into the Frith with a steel truss
bridge a mile long, containing two main
spans of 1700 feet each. Not the least re-
markable and — to those who pay taxes in
New York or Brooklyn to defray the cost
of the " East River " bridge — interest-
ing fact in connection with this scheme
is that it is expected to cost but about
$7,500,000. Who shall say that we are
not making progress in this direction at
least?

The reduction in cost of the purer,
stronger, tougher and more homogeneous
grades of so-called " steel " which are to
take the place of iron in the near future,
and of those which are made by the
" open hearth process," especially, will
depend principally upon the introduction
of the regenerative type of furnace, the
great invention of that greatest of metal-
lurgical engineers, our colleague, Sie-
mens, and of the lesser inventors who
have followed his lead. With this fur-
nace supplying a means of attaining any
desired temperature with a pure mild
flame and at a wonderfully low cost of
production, we are able to produce the
boiler steels and similar metals with an
economy that permits competition in
this field with even the product of the Bes-
semer process. With the closed furnace,
the attainable temperature is only limited
by the temperature of fusion of the ma-
terials of the furnace. Could a new and
sufficiently refractory furnace material be
found, it might possibly be able to com-
pete with the electric furnace of Siemens
or with the electric arc with which our
colleague Farmer, that Nestor among
our electricians, claims long ago to
have produced the diamond. The melt-
ing of platinum in considerable quan-
tities by Ricketts is now a familiar fact
and is an earnest of what may be ex-
pected in the more ordinary departments
of metallurgy when such enormous tem-
peratures shall be found manageable.

We are not yet absolutely free from
annoyance by the presence of air-cells
and minor defects in these u ingot- irons"
as they are properly called : although
such defects have ceased to be dangerous

or in any way very serious. Capt. Jones'
method of compressing the solidifying
ingot by steam pressure, and other de-
vices in imitation of his, are giving us a
very homogeneous metal.

Singularly enough, our people, enter-
prising as we are accustomed to consider
ourselves, have not yet made use of the
Whitworth system of compression of steel,
notwithstanding the fact that its value
has, been known so many years and though
the wonderful strength, uniformity and
toughness conferred by it have made
"Whitworth compressed steel" famous
throughout the world. Abroad, its use
is extending, and guns, screw shafts and
other heavy " uses " are often made of it.
The venerable inventor informs me that
he is preparing plans that will enable even
large castings of peculiar shapes, as screw,
propellors, to be made of this material.
Some dozen years ago, studying this
method and its results, partly for my
own satisfaction and partly to obtain ma-
terial for a report to the Navy Depart-
ment, I was greatly impressed with its
efficiency as even then developed, and its
work has since been wonderfully extended
and its value correspondingly increased.

Our systems of inspection and test of
materials, of parts and of structures are
steadily assuming satisfactory shape and
are becoming very generally, almost uni-
versally, adopted in all important work,
whether public or private, and it will soon
be the exception rather than the rule that
supplies, material or constructions of
whatever kind are purchased without a
careful determination of their fitness for
their intended purpose.

METHODS.

In my last address, I referred very
briefly to the modern method of manu-
facturing machinery in quantity for the
market as distinguished from the old sys-
tem, or lack of system, of making ma-
chines. This method compels the adapta-
tion 6f special tools to the making of special
parts of the machines and the appropria-
tion of a certain portion of the establish-
ment to the production of each of these
pieces, while the assembling of the parts
to make the complete machine takes place
in a place set apart for that purpose.
But this plan makes it necessary that
every individual piece of any one kind
shall fit every individual piece of another

LLU

THE M leu w li\L I \(.i \ EER.

485

kind without expenditure of time and
labor in adapting each to the other.
This requirement, in turn, makes it nec-
-;u\ thai every piece, and every h
and angle, and every hole and every pin
in every piece, shall be made precisely of
this standard size, without comparison
with the pari with which it Is to be paired,
and this last condition compels the con-
action of gauges giving the exact size
which the workman or the1 machine
must bring each dimension.

Finally : In order that this same system
which has introduced such wonderful
momy into the gun manufacture, into
wring machine construction and into so
many other branches of mechanical busi-
ness, may become more general, and in
order to secure that very important result,
a universal standard for guages and for
general measurement, we need anacknowl-
ged standard for our whole country,
one that shall be an exact representation
of the legal standard measure and one
which shall be known and acknowledged
as such, and as exactly such.

It could hardly be expected that private
enterprise would assume the expense and
take the risk involved in this last work.
Such work has heretofore only been done
by governments. Yet among our col-
leagues are found the men who have had
the intelligence, the courage and the de-
termination to accept such risks and to
meet such expense, and the men who have
the knowledge and the skill needed in do-
ing this great work. I think that the
report of our committee od gauges and
the paper of our colleague, Mr. Bond, will
show that this great task has been ac-
complished, and we shall find that we are
indebted to the Pratt & Whitney Co.,
to Prof. Rogers and to Mr. Bond for a
system of measurement and a foundation
system of gauges that will supply our
tool makers and other builders with a
thoroughly satisfactory basis for exact
measurement and for accurate gauging.

It is encouraging to observe that this
subject is attracting the attention of men
of science, and that so distinguished a
body as the British Association for
advancement of Science is taking action
regarding it.

DESIGN.

Design is to-day conducted systemati-
cally and with scientific adaptation of

means to ends. The day of the B<4 d%9'
'int inventor by profession has gone l>v,

and the educated and trained designer ha-

usurped his place. Reuleaux's kinematic

synthesis determines the form to he

taken by the machine when once the <>l>

jeoi Bough! in its construction is plainly
defined, and an intelligent application of

the laws ami data of strength ,,)' materials
gives its parts their safest and most econ-
omical forms and proportions.

The process of invention thus becomes
a scientific one, and the inventor himself,
instead of blindly groping for, or guessing
at. results, is seen intelligently creating
new and useful forms, and is now entitled
j to claim the higher credit and the nobler
; distinction that we gladly accord to him
who performs so high an order of intel-
lectual work and to none more cheerfully
than to him who applies the grand Seience
of Engineering to the production of new
forms of mechanism.

As in the Fine Arts, the great painter
is known by his success in composition
and in form rather than in color, so in our
own art, the best work is that which is
distinguished by excellence of general de-
sign, of arrangement of detail and of pro-
portion, while aimless ornamentation has
no place. This characteristic of true art
will become more fully illustrated as the
scientific method of invention and design
gains ground. The most direct and simple
adaptation of means to end will always
be the object sought by the engineer, and
the labors of one of our honorary mem-
bers, Dr. Reuleaux, have led to the de-
velopment of a scientific method of dis-
covering those means.

HYDRAULICS.

Let us now look in another direction.

The mechaniacal engineer has open to
him as his exclusive province one depart-
ment which is, as yet, only partially de-
veloped in practice, although well ad-
vanced in theory. I refer to that of Hy-
dro-mec/ia/iics, and. especially the utiliza-
tion of water power. Although one of
the earliest opened by the old Greek en-
gineers, it has been one of the latest de-
veloped. Archimides, Ctesibus and Hero
were familial* with the principles of fluid
pressure ; Torricelli, Pascal, Newton and
Bemouilli developed the fundamental
principles of hydro dynamics ; Du Buat,
D' Aubuisson, Prony, Eytelwin and, above

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VAN NOSTRAND'S ENGINEERING MAGAZINE.

all others, Darcy, supplied experimental
data, but it has been reserved for our own
generation to apply the knowledge so
early acquired to the production of effi-
cient hydraulic engines.

But a few years ago, the vertical water-
wheel, as constructed by Fairbairn for
moderate and for high falls, and the un-
dershot wheel of Poncelet, were the stand-
ard wheels in all countries, notwithstand-
ing their cumbrous size, then* slow move
ment and the great cost involved both in
their own construction and in that of their
machinery of transmission. Their effi-
ciency was thought high, although rarely
exceeding 75 per cent. These wheels have
had their day and nothing is likely to
occur to save the whole class from ultimate
disuse.

The turbine, introduced in an effective
form by Fourneyon, a half century ago,
and especially in the late forms of Fon-
taine, Henschel, Jonval, Schiele and
others abroad, and by Boy den and his
successors in the United States, has be-
come the only water-motor in general use.
This small, cheap, quick running wheel
has completely displaced all the older
forms, whether overshot, undershot, or
breast wheels.

The three principal types — parallel, in-
ward flow and outward flow — are all in
use and doing good work.

In Europe, they are all made by good
builders, as here ; but the tendency seems
to be, in the United States at least, to in
troduce most generally another and pecu-
liarly Amercan type, the inward and
downward flow wheel, as illustrated in
the wheel built by our fellow member,
Risdon.

In efficiency, notwithstanding the com-
parative neglect of these motors by scien-
tific investigators, Ihere has been a steady
and important gain during late years.
The improvements which have been felt
out hj makers, working often in the dark
— for few builders claim to understand
the principles of their art and no two, even,
ever agree in their statements of the
principles underlying their practice —
have resulted in a gradual elevation of
standard, until, to-day, a wheel which,
under favorable circumstances, cannot
exhibit an efficiency of 80 per cent, must
drop into the background. I have been
asked to certify a trial giving, as claimed,
95 per cent. ; but that figure could, I am

sure, only be attained by chance, if at
all, when all conditions conspired in its
favor. But wheels are, I have no doubt,
doing work by the day and by the week
at 80 per cent. It may be said that Boy-
den did as well a generation ago. True,
but only with large wheels, built as care-
fully as the chronometer is made, and fit-
ted with polished buckets and diffusers
and tested under conditions purposely
made the best possible. To-day our
builders of turbines give their wheels
such exact proportions and take such
care in the ordinary work of the foun-
dry that they obtain these high figures
from wheels almost direct from the sand.
So far has this change gone that our
theory of the turbine as modified by fric-
tion requires careful revision. Accepting
the older co-efficients for friction and
losses of energy, it will probably some-
times be made to appear, from experi-
mental trials, that the wheels of our best
makers are a trifle better than perfect.
It would seem from figures sent me that
friction, in a well formed wheel, becomes
partly a means of transfer of energy from
water to whe'el, and that the loss of effi-
ciency due to that element is much less
than has been supposed. In some of the
later wheels, losses of energy due to ed-
dies occurring within the flowing mass
have been reduced to such an extent as
to considerably improve their perform-
ance. In the regulation of the turbine, an
excellence has been attained that is
thoroughly satisfactory in some cases, and
the best wheels have been found to give
an efficiency at half and at three-quarters
gate, nearly equal to the best at full gate.
As the efficiency at part gate is often
more important than at full gate, it is
easily seen that this means a vitally im-
portant gain.

MILLING.

A feature of recent progress of general
interest, not only to. engineers, but to
every citizen, is the recent change in
methods of milling.

It has been found that the cutting ac-
tion of the millstone is not best adapted
to the preparation of a good flour ; but
that the crushing action of the mortar
and pestle or of rolls is much more effi-
cient. " Roller Mills "• have been long-
in use in Europe, and the Hungarian
flour, so long noted as the finest in the

THE MECHANICAL ENGINEEK.

4 s?

world, owes itfl excellence, noi simply to
the srluten-chaT&red wheal from which it
is made, but largely bo the systems of
"high-milling" and of cylinder-milling
by which its fine grades are produced
The system of " high milling '' is a pro
cess ol gradual crushing and grinding
by a succession of operations, each of
which gives a finer product than the
preceding, while the intervals between
them permit the grain to lose the slight
heat produced by the slow-running stone.

The first step removes the silica coating
and the grain is next cracked, then bro-
ken up. and finally reduced to tine Hour
without loss of gluten or other injury,
and with less waste than by the familiar
em of "low-milling."
By the latest and best method, the
grain is gradually reduced to fine flour
by passing through a succession of pairs
of rolls. In the great " Walzen-Muhle ''
at Pesth, from eighteen to twenty-four
pairs are used in making the fine grades
of flour. It is this method that is com-
ing into use in our own country, and
our hard north-western wheats are made
by it into a fine, nutritious flour, rich in
gluten, with its grain-cells intact, read-
ily converted into the finest of bread,
and of making 150 to 170 pounds of
loaf per 100 pounds of flour. The
great " Roller- WAX? at St. Paul, Minn.,
has a capacity of production of 500
barrels per day, and the hard wheat of
the north-west supplies it with unex-
celled grain.

TRANSPORTATION.

The modern system of collecting the
grain raised in all parts of our country,
from the Atlantic to the Pacific, from the
Southern States to the great grain raising
districts of Dakota and Manitoba ; the

>tem of storage of the annual product,
which now includes 1.600,000,000 bushels
of Indian com and nearly 700,000,000
bushels of wheat, in the great elevators
of Chicago, Buffalo, New York and Bos-
ton ; these later methods of milling ; our
organization of a meat supply, taking
herds of cattle from Texas for the mar-
kets of the North and East and for trans-
portation to Europe ; our system of pack-
ing meats at St. Louis, Cincinnati and
Chicago, its carnage in refrigerator cars
to the seaboard and in marine refrigera-
tors to European ports ; our methods of

Canning meats &8 well as vegetables, and

ilius preserving themirom season to s.

son : all these now I'a niliai' ways ot re

ducing the cost of living are making fur-
ther advancement toward ;t higher eivil-

i/.ation easier and more rapid 1'liey sup-
ply the first of the two essentials to
healthful progress -cheap food and other

ueeessaril y consumed necessaries of life —

and industrious habits of skilled labor

are then to be relied upon in the the pro-
duction of the permanent forms of weilth.

Our systems of transportation ai
peculiarly the work of the engineer and
are the especial objects of his care. Plan-
ned by great engineers like John Stevens,
John B. Jervis, and others, of whom we
boast as statesmen as well as engineers;
built under the direction of Roberts,
Welch, McAlpine and other great con-
structors, they remain in the hands of
successors skilled in management and
maintenance. All the enormous accumu-
lation of capital in the form of rolling
stock is the product of mechanical engi-
neering, and the thousands of trains daily
speeding accross the land, each represent-
ing in value $30,000 to $150,000 and car-
rying hundreds of human beings or pro-
perty worth from $20,000 to a half million
of dollars, depend for their safety upon the
thoroughness of the builders' work and
upon the coolness, skill and judgment
of the man who handles throttle, brake
and reversing lever — an obvious and forc-
ible reminder of the importance of a pro-
fession, one of the humblest and least
considered members of which is laden
with such enormous responsibility.

ELECTRICITY.

Turning -now to the work of the last
established branch of our profession,
electrical engineering, we find ourselves
still in the midst of a revolution, the prog-
ress of which we are all watching with
unusual interest — the displacement of our
older methods of supplying light and
power by a new system, which, but
lately, was .but the toy of science and
which comes out of the least utilitarian
of all the branches of pure phvsi
Brush has set up his blazing, sun-like,
arc lights in nearly every large city in
the world ; Edison has spread a net-
work of conductors throughout the most
densely settled part of New York City,
distributing many thousands of his

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VAN NOSTKAND'S ENGINEERING MAGAZINE.

clear mellow lights to send their soft,
white rays into corners never yet re-
vealed by the feebler yellow light which
they displace. It remains to be learned
what is to be the cost of the new method
of illumination ; no figures that I consid-
er wholly reliable have yet been given.
It seems sufficiently certain, however,
that the arc light is much more economi-
cal than gas — the same quantity of light
being demanded — for the illumination of
streets, public squares and large interiors,
while interior illumination by the incan-
descent lamps is still considerably more
costly than any other usual method.

The danger to life and property which
come in with the new light are becoming
rapidly less, as safe methods of laying
and connecting the " mains,'' of handling
the plant and especially more careful and
skilful hispection become generally known
and practiced. They still remain so great
as somewhat to retard the introduction
of the electric light.

The secondary batteries of Faure,
Plante and others are likely to aid, after
a time, in bringing the light into use in
many localities in which it would other-
wise be impossible to adopt it with satis-
factory results and in oheapening the cost
of supply. They are still too cumbersome
to be of as great value for general pur-
poses as was hoped when they were first
invented.

Despite every difficulty and every ob-
jection, however, the electric light is
steadily and surely coming into a very
wide field of application. Its beautiful
whiteness, its brilliancy and clearness, its
richness in the actinic rays, and there-
fore its power of revealing every shade of
every color, and of producing the chemi-
cal changes of photogrophy, its freedom
from heat, from vapor and from gaseous
poisonous products of combustion, and
even its curiously interesting effect in pro-
moting the growth of plants, must all
prove qualities of such importance that
its extensive introduction, although hard-
ly its exclusive use, must be soon accom-
plished. As remarked recently by Sie-
mens, gas will long remain the poor man's
friend, supplying his rooms with light, and
probably his kitchen, ere long, with heat.

Little has yet been done in the electri-
cal transmission of power, except to de-
termine experimentally the efficiency of
the system.

I stated last year that the efficiency of
the Edison system had been determined,
and found to be about 90 per cent. Howell's
results have been confirmed by Hopkin-
son, and by Siemens abroad, and are also
checked by reference to Tresca's earlier
work. Recently the Messrs. Gibbs have
made an extended study and test of the
Western machine ; and they also find
the earlier reported figures for electrical
transmission more than confirmed. Tak-
ing the probable efficiency of the two
machines, forming the system in electrical
transmission at 85 per cent, each, we ob-
tain a net efficiency of the system, exclu-
sive of conductor, of above 70 per cent.
— this is precisely Tresca's figure, if I
remember aright — and, allowing liberally
for losses on the line, we may say that 60
per cent, of the power generated may be
utilized. But a good engine of large size
should give a horse-power with 2 to 2J-
pounds of coal per hour, while the small
engines which may be displaced by it will
demand from 8 to 12 pounds, thus giving
an enormous advantage to a system dis-
tributing a large aggregate of power to
many small users. We shall all look with
great interest to the result of actual trial.
The electrical railways at Berlin, in Paris,
and in Ireland, and Edison's road at Menlo
Park, are not likely to remain long unco-
pied. Our own elevated railroad system
offers the best possible field for the utili-
zation of this system ; and the often pro-
posed scheme of burning all our fuel at
the mine, and transmitting light, heat,
and power to our cities along electrical
conductors, begins to seem almost a
practicable one. We may begin to look
once more to thermo-electrical genera-
tion as a possible method of transforma-
tion at the source of power, as proposed
by our distinguished colleague, Farmer,
years ago. The fact that while a 4-horse
power dynamo deposits about 700 pounds
of copper in 24 hours, expending, say
400 pounds of fuel, at least, in usual
work, Farmer deposited 400 pounds of
copper 20 years ago, nearly, with an ex-
penditure of but 109 pounds of coal
burned in his thermo-electric battery, is
an. important one to be kept in mind in
this connection. We may, perhaps, look
soon to see this branch of the subject again
taken up, and a battery again constructed
capable of melting tungsten, and of fusing
8 pounds of platinum in 20 minutes.

Till: MECHANICAL ENGINEEK.

489

Before leaving this subject, it is pleas-
ing to note that in the introduction y^

new electrical units, our great predeces-
sor, James Watt, is accorded deserved
honor beside Ampere, Weber, Ohm,
Coulomb, Volta, and Faraday, and that
so barbarous a system of nomenclature is

made a means of perpetuating the name

i great an engineer, as well as those
of such great physicifi

STEAM.

In steam eng we are not

now advancing rapidly. The introduction
of the •• drop-cut-off*' in 1841, by Sickles ;
of the now standard type of automatic
valve gear in 18-49, by Corliss; of the
high-speed engine, twelve years later, by
Allen and Porter ; of the combined ad-
vantages of jacketing, superheating and
reheating, and the definite acceptance of
the compound engine in later years, still
constitute the complete history of modern
steam engineering; but we are, neverthe-
less, continually gaining a knowledge of
the best methods of handling higher
steam ; of attaining higher piston speed ;
of securing greater immunity from cylin-
der condensation and leakage, and of
providing against other causes of waste.
We are just beginning to perceive what
principles must govern us in the endeavor
to secure maximuni commercial efficiency,
and how economy in that direction is
affected by the behavior of steam in the
cylinder, and by the mutual relations of
all the various expenditures that accom-
pany the use of steam power.

The younger Perkins are still leading
in the practice of carrying high steam,
and make 400 pounds per square inch —
27 atmospheres — is a usual figure while
they are experimentally repeating the work
of the elder Perkins, and of Dr. Albans,
of forty years ago, working steam at 1000
pounds or nearly 70 atmospheres.

Unfortunately, the gain to be anticipat-
ed by the use of these enormously in-
creased pressures does not seem likely to
be very great, unless some decidedly less
wasteful kind of engine can be devised in
which to work it. The " Anthracite," with
steam at 300 pounds and upwards, was
less economical in fuel than the Leila,
carrying about one-third that pressure.
Emery has stated that a limit seems to be
found at about 100 pounds to economical
increase of pressure ; and Stevens finds a
Vol. XXVII.— No. 6—34.

limit due to the peometrica] character

oi the indicator diagram, inside of l>,r)().

One of the most interesting andcurioUS,
as well as important, deductions from the
rational theory of engine efficiency is the
existence of an "absolute limit to econ-
omical expansion," — lying far within the
previous accepted limit — due to the fact of
increase of cylinder condensation and
waste with increase in the ratio of expan-
sion, which places an early limit to the
gain due expansion per Be. If seems pos-
sible, if not certain, that this point us
often actually reached in ordinary engines
within the range of customary practice.

All these facts combined, point to a
probability that we have little to hope for
in the direction of increased steam engine
economy wdth our standard machinery.
Change in the directions that I have al-
ready so often indicated are evidently
to.be our sole reliance — changes limiting
loss by cylinder condensation. Probably
the surrounding of the working fluid by
non-transferring surfaces is our only re-
source, in addition to, or in substitution
for, the now well-understood expedients
of high piston speed and superheating.
Until that is done, steam jacketing re-
mains a necessary and unsatisfactory
method of reducing losses. With a non-
conducting cylinder, were it proem-able,
we might secure very nearly the efficiency
of the ideal engine, friction aside, as it
would be a "perfect engine," and no na-
tural limit would then exist to increasinef
economy. Were this accomplished, we
might at once reduce the cost of steam
power by about one-half in our best en-
gines, and to probably one-fourth or one-
fifth the present cost in ordinary ma-
chines.

In steam engineering, both physicists
and engineers are more than ever at-
tracted to the study of those phenomena
which produce the familiar and enormous
differences, even in the best practice, be-
tween the thermodynamic and the actual
efficiencies of engines. The subject lies
in that "march-land" territory between
science and practice, which few of the
profession can explore from both sides,
and it has remained less known than it
would otherwise be were it either a mat-
ter of j)urely physical science or of prac-
tical experience. Fortunately, we are
likely soon to see it thoroughly studied.
The debate which arose not long since

490

VAIN" NOSTRAND'S ENGINEEEING MAGAZINE.

between Zeuner, the distinguished physi-
cist, as a representative of pure science,
and Hirn, the no less distinguished engi-
neer, as an experienced practitioner and
skilful experimentalist, in which the differ-
ences, to which I have so often called at
tention, of fifty percent, or more between
the " theoretical " efficiency and the actual
performance of the best steam engines,
seem for the 'first time to have been given
prominence in Europe, has led to a
much closer study of the matter than
could possibly otherwise have been
brought about.

On this side the Atlantic, the discus-
sion of steam engineering efficiencies has
been carried on earnestly, if not always
with that knowledge that should precede
criticism, and it is to be hoped and antici-
pated that the engineer may ere loDg be
put in possession of positive facts and real
knowledge that may aid him in so design-
ing and so applying this greatest of mod-
ern inventions as to attain the maximum
marimorum of economy.

Ten years ago, nearly, I took occasion
to state in a report to the President of
the United States on the exhibited ma-
chinery of the Vienna exhibition of 1873,
printed later with the other reports
of the United States Scientific Commis-
sion, that "The changes of design re-
cently observed in marine engines, and
less strikingly in stationary steam en-
gines, have been compelled by purely
mechanical and practical considerations.
The increase noted in economy of ex-
penditure of steam and of fuel is, as has
been stated, due to increased steam-press-
ure, greater expansion, and higher piston-
speeds, with improved methods of con-
struction and finer workmanship. These
several directions of change occur simul-
taneously, and are all requisite. To se-
cure maximum economy for any given
steam-pressure, it is necessary to adopt a
certain degree of expansion which gives
maximum economy for that pressure
under the existing conditions.

"This point of cut-off for maximum
efficiency lies nearer the beginning of
the stroke as steam-pressure rises. For
low pressure a much greater expansion
is allowable in condensing than in non-
condensing engines ; but, as pressure
rises, this difference gradually lessens.
For example, with steam at 25 pounds

are obtained when expanding about three
times in good condensing engines and
about one and a half times in non-con-
densing engines. With steam at 50
pounds, these figures become five and
two and a half, respectively ; and at 75
pounds, the highest efficiency is secured
in condensing engines, cutting off at one-
fifth, and in non-condensing engines with
cut-off at one-third stroke.

" Owing to the decreasing proportional
losses due to back-pressure and to re-
tarding influences, the departure from
the economical result indicated for the
perfect engine becomes greater and
greater, until, at a pressure of between
200 and 250 pounds, the proper point of
cut-off becomes about one-sixth or one-
seventh, and very nearly the same for
both classes of engines, and the increase
of efficiency by increase of pressure and
greater expansion becomes so slight as to
indicate that it is very doubtful, whether
progress in the direction of higher press-
ure will be carried beyond this limit."

These conclusions were derived from
careful observation of the performance
of unjacketted "single cylinder" engines
and a comparison of the ratios of ex-
pansion of those exhibiting greatest
economy. It is interesting to note that
later, and probably reliable methods of
comparison than were then familiar go
far in confirmation of the opinion then
expressed. I think that I have been able
to prove the existence, as just stated, of an
" absolute limit of economical expansion,"
which, whatever the ratio of steam press-
ure to back pressure, in all ordinary heat
engines probably falls within the range
of familiar practice. Advance beyond the
best efficiency of to-day in ordinary en-
gines seems likely to be very slow and
not at all likely ever to be very great.
Extended experiments will be needed
to secure all the facts demanded by the
designing engineer and to furnish con-
stants for the approximate theory of
efficiency, which only is, as yet, his sole
guide. An exact theory is one of those
things for which he hopes but which he
does not expect soon to see. Some ex-
periments have already been made, but
they contribute only the first step.
Those made by order of the Navy De-
partment, and principally by Isherwood,
and those of Hirn have hitherto been
by gauge, the best economical results I our sole guide, but a new line of more

Tin: MECHANICAL ENGINEER.

•11)1

direct investigation of the laws govern-
ing internal, or cylinder, condensation
has been inaugurated byEscherof Zurich,
and we arc able to see a fair prospect of
obtaining definite information in tliis
direction.

Escher finds, in the case taken by him
that this waste variesnearly as the square
of the period oi revolution and of
the pressure, and is nearly independent
of the back pressure— conclusions which
are especially interesting to me as cor-
•rating assumptions, based on general
observation and non-experimental prac-
Miade by me previously in develop-
ing an empirical system of design.

In steam boiler engineering, the only
observable change seems to be the slow
but steady gain made in the introduction
of water-tube coil boilers and sectional
boilers, and in the extension of a rational
system of inspection and test while in
operation. To-day, the intelligent owner
of boilers secures inspection and test, with
insurance, by intelligent engineers and
responsible underwriters, as invariably as
he obtains inspection and insurance of
his buildings. Under this system, steam
boiler design, construction and manage-
ment is becoming a distinct art, based
upon real knowledge. The system of
forced circulation proposed by Trow-
bridge, and, perhaps, others, seems to
me likely to prove useful in the solu-
tion of the problem to-day presented.

MARINE ENGINEERING.

In Naval Architecture and Marine
Engineering, the fruits of the labors of
our colleagues are seen in the constantly
growing magnitude of our steamships,
and in the steadily increasing celerityand
safety which mark their unceasing transit
from continent to continent.

The " Alaska " makes trip after trip, as
regularly as a ferry boat in all but the
most trying weather, from Sandy Hook
to Queenstown in a week, and has made
18 knots an hour for 24 hours together,
and the " Arizona " and the " Servia " are
closely rivaling this wonderful perform-
ance.

A half dozen years ago I was con-
sulted by an interprising steamship pro-
prietor who desired to learn how far the
substitution of steel for iron would aid
in the attainment of his aim — the con-

struction of a line of steamers to make
25 miles an hour from shore to shore.
A similar project has been lately dis-
cussed and it would not be surprising to
the well-informed engineer if the plan is
Carried out within this decade.

Even the ill-famed line between Dover

and Calais and other channel routes are
benefitting at Last by the achievements
of the mechanical engineer and the

u Invicta," a steamer considerably smaller
than the "Pilgrim," has crossed the chan-
nel in fair wreather in a little over one hour
running time — a speed of IS knots, or 21
miles, an hour — and the " twin " steamer
" Calais-Douvres " makes the passage in
an hour and a half so steadily that the
trying scenes so unpleasantly remem-
bered by every unfortunate who has
crossed on the old boats no longer oc-
cur.

This most attractive and difficult of
problems presented to the engineer —
to secure a maximum, speed, combined
with good cabin accommodations and
paying cargo capacity — demands an ex
tent of knowledge and experience, an
ingenuity and a degree of practical skill
which are demanded by no other task set
before the engineer.

My attention has been called to this
subject more strongly than ever before,
by experiences arising recently in my
own practice, and I have been interested
in observing how largely the problem
resolves itself into one of boiler con-
centration. The engineering of the ma-
chinery is a minor matter ; to get a
maximum of steam production from a
i minimum space and weight in the boiler-
room and coal-bunker compartment is a
vitally important matter. Even where
the cargo space is surrendered, it is
difficult to secure speed and good cabins
in small steamers, and the scheming of a
high speed yacht of ample accommoda-
tions and of good sea-going qualities is
a most perplexing piece of work.

Not the least remarkable work in this
department has been done, however, on
very small craft. Torpedo-boats require
but little weight — carrying displacement
— and can be loaded with machinery, and
thus the disadvantage of their small size
is, partly at least, compensated. They
have been given astonishing speeds, but
only by forcing boilers tremendously to
drive the lightest of engines in the light-

492

van nostrand's engineering magazine.

est possible hulls, over, rather than
through, the water.

The art of getting high speed is ex-
tremely simple in principles but very
difficult in practice. It embraces a very
few essential requirements : — (1) Light-
ness of hull ; (2) excellence of form ;
(3) minimum weights carried, whether in
cargo, accommodations, fuel or machin-
ery ; (4) great impelling power, *. e., for
best work, a steel hull ; small cargo ;
few stores; fuel for the least time per-
mitted by ordinary prudence ; contracted
cabins ; small engines driven at the
highest attainable speed of piston and
by maximum safe steam-pressure, and
finally, and perhaps, principally, boilers
of small size, carrying high steam, with
minimum water space and forced to the
very limit of their power. The art of
getting large grate area into a contracted
and peculiarly-shaped cross-section of
hull is one still to be learned.

The torpedo boats of Thorneycroft
and Yarrow in England, and of Herres-
hoff in the United States illustrate the
most successful practice of to-day, and
their attainment of speeds exceeding
twenty miles an hour may be accepted
as the most remarkable triumphs of re-
cent mechanical engineering.

With light hulls, weighing but about
one-third their displacement, having such
fine lines as to occupy but six-tenths the
circumscribing cylinder, burning 100 to
150 pounds of fuel on the square foot
of grate, carrying 120 pounds of steam,
their little engines making 800 to 900
feet of piston speed per minute, at from
500 to 700 revolutions, and weighing
but 50 or 60 pounds to the horse-power,
this kind of work is locomotive prac-
tice of the most radical sort. The secret
of success here lies largely in ability to
drive the boilers, which are of the loco-
motive type, forced by powerful fan
"blowers," and give a horse-power to
each 1£ or 2 square feet of heating sur-
face and from 20 to 30 horse-power to
the square foot of grate.

Now that we are using surface con-
densation exclusively, there is compara-
tively little difficulty in the introduction
of locomotive practice at sea.

But remarkable and important as is
this phase of steam engineering, these
little craft have revealed in their per-
formance, facts of equal importance in

another department. The speeds attained
are high, even for large ocean steamers ;
they are enormously high for such small
vessels. It is found that, passing the
speeds of 10 or 12 knots, which corre-
spond to high speeds in larger craft, the
rate of variation of resistance passes a
maximum and then falls from variation
as the cube of the speed, or higher, to
the j- power and becomes finally directly
proportional to the speed at their highest
velocity, thus giving a comparatively
economical performance.

Should the same change of law occur
with large steamers, maximum railroad
speeds at sea may yet prove to be attain-
able, when, as I have no question will,
ere many years be the case, we shall
burn at sea a hundred and fifty pounds
on the square foot of grate in locomo-
tive or sectional boilers, with steam at
200 or 300 pounds pressure, driving
engines at 1000 or 1500 feet piston-
speed per minute, turning screws fitted
with guide blades as already practiced
abroad, and with machinery of steel in
steel hulls of less proportional weight
than these torpedo-boats.

It is by such changes as these that
the mechanical engineer and his col-
leagues in the trades is gradually revo-
lutionizing the art of war. Before many
years, we hope, war will be made so
destructive that no nation will dare ven-
ture into a naval contest, and the engineer
will have then entitled himself to the
glorious distinction of being victor over
victory itself. He may thus bring about
the death of all war, and may give new
meaning to Schiller's song :

" Honor 's won by gun and sabre ;
Honor 's justly due to kings ;
But the dignity of labor
Still the greatest honor brings."

The screw has become the only instru-
ment of propulsion where it can be used,
and can see no reason to suppose that it
will not so remain indefinitely ; but engi-
neers, who have hitherto been blindly
groping to find some new and peculiar
form which may possess mysterious
principles of efficiency, have now become
fully cognizant of the analogy between
the screw propeller and the turbine, and
are seeking to apply the well-developed
theory of the latter to the former.

The value of a system of guide blades
and of methods of direction of the cur-

THE MECHANICAL ENGINEER.

493

rents approaching and leaving the screw
is being determined experimentally, and
it is to be hoped that, before long, we
may see this instrument rival the better

classes of turbine and exhibit an etVicien-
l so per cent, and upward. Thorney

croft has already done good work in this
direction.

AERONAUTIC.

It is the reduction oi weight of hull

and machinery, so remarkably exempli-
fied in recent naval engineering, and the

no less remarkable recent improvement
in performance that renders it more than
$ible that we maybe on the eve of
real advancement in aeronautics.

In my last address, I referred to the
work done up to that date and endea-
1 to Bhow how far the researches of
Marey, of Pettigrew, of De Laucy and
Haughton had developed the experimen-
-cience of aeronautics, and how far
the efforts of Dupuy de Lome had
supplemented the labors of the brothers
Hontgolfier, of Charles, of Greene, of
Flammarion and of Glaisher in actual
navigation of the air. I took occasion to
indicate what seemed to me to be the
promise of the early future and the indi-
cations of ultimate success.

Since then, little or nothing has been
done, either in research or in aeronautic
practice, but Pole has made a study of
the problem, and from known data, has
determined what we may probably ex-
to see accomplished when, as may
soon occur, the modern methods of
locomotive and marine engineering shall
be applied to aerial steam navigation by
means of balloons. He studies the prob-
lem as outlined by Lavoisier, a century
ago, 1783, as attacked by Gififard a gene-
ration ago, in 1850, and as so nearly
solved by him and by Dupuy de Lome
during the Franco-German war. Both
attained speeds of between 6 and 7 miles
an hour in " derif/eable " balloons.

Calculating, from known data, the nee-
essary size of balloons to carry the de-
manded weights, obtaining by direct re-
ference to known performance the prob-
able resistance of the air-ship, taking the
possible least weight of metor at 40
pounds per horse-power, net, 50 pounds
gross and 75 pounds including the con-
denser, and allowing for nearly 20 tons
of cargo, Pole finds that, a balloon, of

spindle form, 100 feet in diameter and
370 feet long may be driven by this tor-
pedo boat style of machinery at the rate
of about 30 miles an hour. An air-ship

o\ one half these dimensions would steam

'20 miles and one built on one-third scale
12 miles an hour.

These are certainly interesting and re-
markable figures; but, as their author
remarks, they come fairly and legiti-
mately from existing data. Should the
time ever come when the practical diffi-
culties of construction can be fully ov<
come, it is evident that success in aerial
navigation will promptly follow, and we
may hope that the time is not far distant
when this new product of modern me-
chanical engineering may become practi-
cally useful to the world.

To-day, however, man with all his
vaunted intelligence and with all his wron-
derful powers, is in this field beaten by
every bird that flies and even by the so
minute an insect as the gnat, which is
only to be seen when disporting in the
sunbeams.

Elmirus and Joseph Degnan have, as ■
yet, no followers known to fame, and
stand beside Bushnell and Fulton who
inaugurated submarine navigation, but
I yet are without successors.

CAPITAL AND LABOR.

In singular and discreditable contrast

! with all this gain in recent and current
practice in engineering stands one fea-

! ture of our work wdiich has more im-
portance to us and to the world, and

- which has a more direct and controlling-
influence upon the material prosperity
and the happiness of the nation than any

! modern invention or than any discovery
in science. I refer to the relations of
< ntployers to the working classes and to
the mutual interests of labor and capital.
It is from us, if from any body of men,

i that the world should expect a complete
and thorough satisfactory practical solu-
tion of the so-called " labor problem.''
More is expected of us than even of our
legislators. And how little has been
accomplished !

Yet it would seem that the principles
involved are simple and that the practi-
cal difficulties should be readily over-
come. The right of every man to buy or
sell labor wherever and whenever he may
choose and wherever and whenever he

494

van nostkand's engineeeing magazine.

can make the best bargain is one of those
rights which are natural and inalienable.
The right of every man to engage in any
occupation, or to enter into any depart-
ment of honest industry, to train his
children for any productive occupation,
or to secure for them any kind of em-
ployment, is an equally natural and ina-
lienable right. The privilege of accumu-
lating property to any extent and by any
honorable and legitimate means, is also
naturally and legally accorded to every
citizen. It would seem obvious that one
of the first claims of the citizen upon the
State is that he shall be absolutely as-
sured of these as constitutional rights.
Any infraction of such rights and any
attempted contravention of such privi-
leges, whether by individuals, by legally
constituted corporations or by associa-
tions unknown to the law, should be
promptly dealt with, and so severely,
whether the culprit be of high or low
degree, that the offence shall not be
likely to be repeated.

No legislation should be permitted
that shall injuriously affect any morally
unobjectionable industrial enterprise or
that shall impede any fair commercial
operation, whether .in the exchange of
commodities or the transfer and use of
capital. Only such a tariff system, even,
can be safely permitted as shall encour-
age fairly the growth of such new indus-
tries as are adapted to our climate, soil,
and other natural conditions.

The prosperity of a people is depend-
ent upon their industry, integrity, skill
and enterprise, as well as upon the natural
resources of the country, and the object
of every government and of all legislation
is to protect the people in their right to a
fair reward for their industry, skill and
enterprise, to promote that mutual confi-
dence that comes of real business trust-
worthiness, and to develop the natural
resources and advantages of the State.
The protection of the individual in his
right to learn, to labor and to traffic; the
encouragement of natural enterprises, the
diversification of industries, the promo-
tion of the ability of the people to pro-
duce valuable materials and all kinds of
products of the higher classes of skilled
industry, the encouragement of invention
and the making of the nation independent
of all possible rivals or enemies in the
production of whatever is necessary to

the existence or the comfort of the peo-
ple, are all perfectly proper objects of
legislation. No legislation which neg-
lects or opposes these objects can aid us.
No legislation can serve the nation which
aims to help either the employer or the
employe, either the capitalist or the
laborer, alone. No industry can perma-
nently succeed which does not make both
classes prosperous, and no statecraft is
deserving the name which does not aim
at the support of both. If either is dis-
couraged and driven out of the field,
business ceases and suffering results.

Again, force and intimidation have no
place in matters of business. All legiti-
mate operations, whether in commerce or
manufactures, are the result of mutual
agreement for mutual advantage. Strikes-
and lockouts, as well as their usual, but
shameful, concomitants, intimidation and
violence, are wholly out of place in our
industrial system and should be repressed
by every legal means, as absolutely op-
posed to the spirit of civilization and to
the letter of our Declaration of Independ-
ence. The simplest principles of political
economy and social ethics cover this mat-
ter fully. Labor, like any other salable
possession, will have a value determined
accurately by the great law of supply and
demand, and the interruption of traffic in
labor, and at the same time the compul-
sory interruption of production, in the
end only result in serious injury to both
parties to the controversy and to the
whole country as well.

The introduction of a general system
of arbitrament, the formations of unions
between associated employers and of asso-
ciated employes, the diversion of the
trades unions into their legitimate chan-
nels of usefulness will ultimately, we may
be sure, effectually reform all the existing
abuses in this direction. Already work-
ingmen are learning that strikes almost
invariably cost far more than they gain ;
capitalists are beginning to understand
that their pecuniary interest, as well as-
ordinary humanity, dictate careful consid-
eration of, and respect for the rights
and interests of labor and, ere long,
when employers sustain labor ex-
changes in all our great cities and when
trades unions confine themselves to
benevolent enterprises and the assistance
of those members who desire to reach
better paying fields of labor, we may ex-

THE MECHANICAL ENGINEER.

495

peel to Bee every industry settle down to The professional politician Bud the ma-
chine system must become extinct. Our
public policy and our law making must
be made subservient to industrial inter-
ests. Tin; people, and not self-seeking

ward politicians, must frame the code and

direct the expenditure of public funds.

a steady, unintcrmitted routine which will
give maximum production while every
worker will have uninterrupted employ-
ment at rates o( pay which will be the
maximum value of the labor sold. If
every boy were made familiar witli
Nordhoff and every man with Adam
Smith and Spencer and Stuart Mill, we
might hope that it would become univer-
sally understood that highest prosperity
can only come when business can proceed
without interruption by strikes, lockouts,
or unintelligent legislation. A perusal

SYSTEMATIC PROMOTION OF INDUSTRIES.

And these considerations bring up the
question : — How can so desirable a change
in politics and in industry be brought
about ?

There is but one answer : By systematic

of Eaton's excellent report on Civil Ser- 1 and carefully planned encouragement of

vice suggests the thought that such a

-tern is as desirable in every industrial
organization as it is in the public service.

Grimm, in his life of Michael Angelo,
says that three powers rule every state,
and they are variously classed as "Money,
Mind, Authority," as "Citizenship, Science,
Nobility, " or "Energy, Genius, Birth."
I would say, in each individual, " Talent,
Power and Character," or " Genius,
Strength, Integrity" are ruling powers,
but that we are yet to see them rule the
State. That the time is coming we may,
I am sure, both hope and believe, but a
great change must first take place.

We need a Junius to write, a Burke
to speak, and a Chatham to illustrate a
real reform.

The elements of social economy are yet
to become known to our people; the most
obvious principles of statesmanship are
yet to be learned by our legislators, and we
have still to look forward to a time when

all industries, a system that shall illus-
trate those methods wdiich are the true
object of all government, a bystem, also,
which shall supply means by which full
advantage may be taken of all those op-
portunities, which present themselves to
every citizen of the United States.

Such bodies as this must aid our
legislative assemblies in developing a
scheme of industrial organization, that
shall exhibit highest possible efficiency —
one that wTill prepare the children and
youth of the country to enter upon lives
of maximum usefulness, and to do the
work that may be given them to do with
ease and comfort, while, at the same time
aiding them to attain health, happiness
and content, even if not independence
and wealth.

It is easy to see what must be the
leading features of such a system.
Since the prosperity of the State and of
the people depends upon the integrity,

ournien of business and our working peo- the skill and the industry of its citizens
pie shall be fairly and respectfully consid- j it is
ered by those who direct public policy.
Before the needed reform can be made pro-
ductive of general good, we must return to
the original theory of our government —
that all government has for its object sim-
ply the preservation of the rights of the
people in their pursuit of the best life,
the highest liberty and the purest happi-
ness ; that it should guarantee to all, of
whatever race, creed, powers or sex, a com-
mon right to live, to learn, to labor and
to acquire and hold property, with abso-
lute freedom of thought, speech and right-
doing.

To attain all that we desire and to se-

evident that the cultivation of good
morals, a keen sense of right and a high
sense of honor are primary requisites ;
that the instruction and training of every
youth in the art for which he is best
fitted is essential : that a fair general
education is equally necessary to afford
sources of intellectual pleasure ; that a
reduction of the hours of labor to a mini-
mum healthful length must, give oppor-
tunity for continual self-improvement and
for healthful recreation.

It is obvious that we must find ways
of encouragement of those industries,
the success of which are best assured by
our climate, our soil, our topography,

cure highest efficiency in our political and and by our social and political conditions,
social system, we must have a business We must take steps to secure by syste-
man's and a working man's government. | matic legislation and by every other

496

TAN NOSTRAND'S ENGINEERING MAGAZINE.

proper means a diversification of skilled
industries and such a relative distribu-
bution of agricultural and manufacturing
population as shall bring to each all the
necessaries and comforts of life at mini-
mum cost.

It is our task to study the soils, cli-
mates and natural resources of this wide
land of ours, to learn what products of
the soil and what manufactured articles
can be made to give the best return for
time and money invested, and then to
systematically develope by public policy
and private enterprise, every such in-
dustry, securing the highest skill, the
most reliable labor and the finest artistic
talent by conscientiously cultivating
them. Skilled labor has a steadier market
and makes a steadier market than un-
skilled, and our effort should evidently
be to lead the world in its development,
cultivating all profitable manufactures
which demand greatest skill and highest
talent ; encouraging a varied industry ;
making the expenditure of capital and
labor on transportation and on coarse
work a minimum, and making the most
of every pound of raw material brought
into our market before putting it on sale
again. Any system of encouragement of
domestic industries that may be adopted
must evidently include a practical and
fruitful plan of careful education and of
regular training in the trades and arts
capable of successful growth among us,
making our people the equals, and, if
possible, the superiors of their competi-
tors in other countries, in intelligence,
skill, knowledge and enterprise. It must
introduce new industries and diversify
old ones. It must teach the child, train
the youth and protect the man from ex-
cessive outside rivalry.

Only when our whole population has
become as intelligent, as skillful and as
well informed in every branch of every
industry, existing or arising in the State,
as any other people can possibly be, only
then, may we rely safely upon profiting
fully by all those advantages due to our
natural position and resources.

Such a plan must be carefully con-
sidered by the sages of the community,
and only adopted after deliberate study
and thoughtful consideration. But a
few general principles are readily dis-
coverable. A half dozen years ago, at
the request of a commission appointed

by the State of New Jersey, of which
commission I had the honor to be ap-
pointed secretary, I prepared a general
outline of such a scheme as that which
now interests us, and based it upon the
following " platform " :

Such a plan, to be satisfactorily com-
plete, must comprehend:

A common school system of general
education, which shall give all young
children tuition in the three studies
which are the foundation of all education,
and which shall be administered under
compulsory law, as now generally adopted
by the best educated nations and States
on both sides the Atlantic.

A system of special adaptation of this
primary instruction to the needs of
children who are to become skilled artis-
ans, or who are to become unskilled
laborers, in departments which offer op-
portunities for their advancement, when
their intelligence and skill prove their
fitness for such promotion, to the pos-
ition of skilled artisans. Such a system
would lead to the adoption of reading,
writing and spelling books, in which the
terms peculiar to the trades, the methods
of operation and the technics of the in-
dustrial arts should be given prominence,
to the exclusion, ii necessary, of words,
phrases and reading matter of less essen-
tial importance to them.

A system of trade schools, in which
general and special instruction should be
given to pupils preparing to enter the
several leading industries, and in which
the principles underlying each industry,
as well as the actual and essential man-
ipulations, should be illustrated and
taught by practical exercises until the
pupil is given a good knowledge of them
and more skill in conducting them.
This series should include schools of
carpentry, stone cutting, blacksmithing,
etc., etc., weaving schools, schools of
bleaching and dyeing, schools of agri-
culture, etc., etc.

At least one polytechnic school in
every State in the Union, in which the
sciences should be taught and their ap-
plications in the arts indicated and il-
lustrated by laboratory work. In this
school, the aim should be to give a cer-
tain number of students a thoroughly
scientific education and training, prepar-
ing them to make use of all new dis-
coveries and inventions in science and

THE MECHANICAL ENGlH BER.

41)7

art, and thus to keep themselves in the

front rank.

A system of direct encouragement

existing established industries by every

legal and proper means, as by the encour-

ement of improvemenl in our system

transportation, the relief of important

undeveloped industriefl from State ami

municipal taxes, and even, in exceptional

by subsidy. It is evident that

such methods of encouragement must be

very circumspectly and with

eedingly greal caution, lest serious

abuses arii

This Bystem should comprehend, per-
haps, a Bureau of Statistics, authorized,
under the law creating it, to collect sta-
ies and information relating to all de-
rtmentfl of industry established, or
of being established in the

I would place, as the head of this whole
stem of aid and encouragement of all
.itimate industries, a great central Uni-
rsitv of the Useful Arts and Sciences
which should be the directing member of
the whole organization, furnishing higher
instruction to the son of every citizen
who can find his way to it, supplying the
polytechnic schools and colleges with the
most learned and talented instructors,
aiding bv scientific investigations the de-
velopment of every industry, and serving
as an attractive nucleus around which
should gather the great men of every
department to serve the State in that
highest of employments, the instruction ,
and training of our youth, and by giving |
counsel to legislators and executive ,
officers of every department of the Gov- 1
eminent, in concert with our already es-
tablished National Academy of Sciences.
Washington urged the creation of a
National University, a primary object
of which should be the education of
youth in the Science of Government.
Jefferson, also, urged the foundation of
"a National Establishment for Educa-
tion,'' and John Stuart Mill has said,
•• National institutions should place all
things that are connected with them-
selves before the mind of the citizen in
the light in which it is for his good that
he should regard them."

Experience at home and abroad shows
that systematically conducted schools of
art, and trade schools, are vastly more
efficient and economical in the education

and training of youth than the best

managed mill or workshop. Every oper

ation can there be taught, and the learner
made perfectly familiar with each detail,
without causing the inconvenience and

pecuniary loss which are sure to come

With suc'h an attempt in the shop.

Very much such a complete system <>t
technical science of instruction and of in-
dustrial education has been incorporated
into the continental educational struc-
ture, and there places before everyohildin
the land the opportunity of giving such
time as the social position and pecuniary
circumstances of its parents enable them
to allow to devote to the study of just
those branches which are to it of most
' vital importance, and to acquire a syste
matic knowledge of the pursuit which
surrounding conditions or its own predi
lections may lead it to follow through
life, and to attain as thorough a knowl-
edge and as high a degree of skill as
that time, most efficiently disposed, can
possibly be made to give him. There is
here no waste of the few months, or years
of, to him, most precious time, which the
son or the daughter of the humblest art-
isan can spare for the acquisition of a
limited education. Every moment is
made to yield the most that can be made
by its disposition in the most thought-
fully devised way that the most accomp-
lished artisans and the most learned
scholars, mutually advising each other,
can suggest. One day, in such schools
as those here described, is of more value
t ) the youthful worker than a week in
! the older schools, or than a month in the
workshop or the mill. Thus, while the
fact is recognized that a general and a
liberal education is desirable for every
citizen, the no less undeniable fact is also
recognized that few citizens can give the
time to, or afford the expense of, a sym-
metrical general course, and that the
interests of the individual and of the
State unite in dictating the provision of
such systems and means of industrial
education and training as are now actual-
ly provided.

It is in consequence of the adoption of
an intelligent and extensive system of
the character of that which I would pro-
pose for our own country that it has
become now generally admitted that
Germany is the best educated nation of
the civilized world. (There is danger

498

VAN NOSTRAND'S ENGINEERING MAGAZINE.

that the United States may, with reason,
be reckoned the worst.) Germany is
gaining a better industrial position daily ;
our own country is retrograding in all
that tends to give manufacturing pre-
eminence, except in the ingenuity, skill
and enterprise of its people ; and the
one great, the vital, need of our people
is a complete, efficient and directly appli-
cable system of technical instruction and
of industrial training, if they are to avoid
the successful and impoverishing compe-
tition of nations which have already been
given that advantage^by their statesmen
and educators a generation earlier. The
question whether this comparison shall
remain as startling and as discreditable
to the people of the United States in
future years as it is to-day, is to be de-
termined by the ability of our people to
understand and appreciate the import-
ance of this subject, by the interest which
the more intelligent classes may take in
the matter, and upon the amount of in-
fluence which thinking citizens and edu-
cated men and the real statesmen among
our legislators may have upon the policy
and the action of the general and the
State Governments. The promptness
and energy which we may display in an
effort to place ourselves in a creditable
position among educated nations, will be
the truest gauge of the character of the
people of the United States. Judged by
her progress in this direction, Europe is
far in advance of us in the most essential
elements of modern civilization.

There, instead of standing aloof from
each other, and instead of forgetting, as
is too frequently the case in our own
country, those great facts and those im-
perative duties which every statesman
does, and which every citizen should,
recognize, the governing and the educated
classes, have worked together for the
common good, and have given Germany,
especially, a vantage-ground in the uni-
versal struggle for existence and wealth
which is likely, in the future, to enable
that country for many years steadily to
gain upon all competitors.

Our own work, thus far, has been des-
ultory, sometimes ill directed, and rarely
thorough or systematic. Our " techni-
cal schools," so-called, are often modified
trade schools, and our few trade schools
frequently aspire to the position of poly-
technic schools, and both classes are con-

founded in the minds of very many, even
in the profession, and their work is sel-
dom done with that maximum efficiency
which can only come of intelligent organ-
ization and definite aims and fields of
work. So it happens that while the sys-
tem of general primary education is more
widely spread and more effective than in
any country in the world, and while we
have a larger number of schools, in propor-
tion to population, than perhaps any other
country, we are nearly destitute of trade
schools, and have extremely inadequate
provisions for industrial education of
any kind and for any class of our people.
This system of preparation of every
citizen for useful work and a prosperous
life being adopted, there remains to be
considered what can be done to aid the
great industries into the channels of
which all this skill and training in the
arts and applied sciences is to be di-
rected. •

GENERAL CONCLUSIONS.

A complete working system of prepar-
ation being inaugurated, all is done that
can be done for the individual in the
endeavor to place him on a fair vantage
ground in the struggle for survival which
is going on throughout the world. Be-
yond this, he must trust principally to
his own intelligence, skill, industry and
frugality for success in the effort to se-
cure the necessaries and comforts of life,
and to acquire luxuries, a comfortable
independence in old age, and the means
of starting his children on a higher level
than that which he has himself reached.

A plan for the encouragement of our
industries and to secure permanent pros-
perity must include a general policy of
legislation which shall aid the capitalist
to safely invest his funds in manufactur-
ing enterprises, or in agriculture, shall
assist the working man and the working
woman to find remunerative and perma-
nent epiployment, shall protect everyone
in the right to sell his capital or his labor
at the best market value, wherever and
whenever he chooses to offer it, and to
give and to take in fair bargains without
let or hindrance.

Such a policy must sustain every good
workman in the effort to secure a good
price for his labor and every employer
against every attempt to compel him to
pay good wages for bad work or to sur-

THE MARINE BOILER.

499

render the control of his business or his
property to any other man.

Legislation must be general and must
so far as possible, avoid either direct or
indirect interference with the natural
currents of trade. It must facilitate,
not obstruct, natural industrial move-
ments. The welfare of the people, and
not of any class, rich or poor, must be
studied

The fruit of such a system as I have
outlined will be fully seen only when all
our labor is skilled and intelligent; when
all our directors of labor are familiar with
the science of their art, and when our men
of science are all men applying science.

Kenan, in his autobiography, expresses
his conviction that succeeding genera-
tions will be taught principally natural
sciences, for the reason that the truths

learned in their study have more import
anee to mankind and have a deeper inter
est than the facts of history or the accu-
mulated stores of general literature.

Men of Science and Men of Art. too, are
becoming known and acknowledged as of
most importance to mankind and as the
principal reliance of the race in its terri-
ble struggle against poverty, disease,
misery and death. The influence and the
power of men who devote themselves to
the study of the phenomena of nature,
and of those who make useful application
of a knowledge of nature's facts, laws
and forces, must inevitably and continual-
ly increase so long as civilization shall
continue to advance.

The world will finally reward most
nobly those who thus most nobly strive
to forward its highest aims.

THE MARINE BOILER*

From the "London Times.

Mr. Shock, of the United States Navy,
is the author of a treatise on steam boil-
ers, which, for comprehensiveness and
thoroughness of treatment, and fullness
of illustration, may serve as a model for
English engineers. It is at once theo-
retical and practical. Beginning with
chapters on the nature, process, tempera-
ture, and products of combustion, and
upon the law of transmission of heat
and evaporation, the author subsequently
directs the attention of the reader to a
consideration of the materials of which
boilers are made, and of the principles
which should determine their design,
construction, and management. His
plan of treatment is thus systematic and
progressive. The young engineer is
taught not only what constitutes an
efficient steam generator, but why effi-
ciency results from the observance of
certain conditions of form, and the pro-
portional ratios of heating surfaces to
water space and steam pressure. There
are also chapters on the deterioration of
boilers, and upon boiler explosions.

It is an axiom in mechanics that the

* "Steam Boilers: Their Design. Construction, and
Management." By William H. Snock, Engineer-in-
Chief United States Navy. New York : D. Van Nos-
trand.

strength of a structure is determined by
the strength of its weakest part. Now,
there can be little question that the
weakest part of a man-of-war or an ocean
steamer is its steam-generating appar-
atus. The engines propel the ship, but
they can only transfer to the ship in the
form of motion the power which they
derive from the boilers in the form of
pressure. The mere circumstance that
Mr. Shock has written a voluminous
quarto treatise on the construction and
management of steam boilers, illustrated
with upwards of 30 pages of plates, is
enough to prove that much is to be said
upon the subject, and that the stage of
finality has not yet been attained. For,
while the boiler is a source of power, it
is also a source of weakness and of con-
stant anxiety and watchfulness on board
ships. Its complicated ramifications, and
the difficulty which it offers to inspection
render it, even under uniform and normal
conditions, very liable to get out of repair.
In a man-of-war, however, where it is
subjected to continual fluctuations of
pressure — sometimes being forced until
the steam lifts the safety-valves, and at
other times only pushed a little over the
atmospheric pressure — it is still more

500

VAN NOSTRAND S ENGINEERING MAGAZINE.

liable to wear itself out, and exhibit un-
expected infirmities long before the
period of old age is reached. It is the
chief element of trouble and danger
against which the marine engineer has to
guard ; and in all naval services, and
certainly in ours, the orders and regula-
tions which are issued for the manage-
ment and preservation of boilers are
more numerous and stringent than those
issued .with reference to any of the other
manifold equipments of a ship of war.
The boiler may explode and produce
other explosions. In the case of the
Thunderer, the explosion was caused by
the closing of the stop-valve and the
simultaneous jamming of the safety-
valves. An explosion may also occur
through inattention to the water gauges,
to internal incrustation, or to inherent
weakness. But accidents of this kind,
to whatever secondary causes they may
be due, are, as a rule, the result o-
carelessness on the part of the enginef
room staff. Boiler explosions may be
practically regarded as preventible. But
ship's boilers are sadly liable to get out
of order by the persistent use of the
blast, by the formation of saline de-
posits, by wear and tear? by the intrusion
of fatty matter from the warm well, by
pitting, by the introduction of moist
air, and from other causes of deterior-
ation for which the Admiralty Boiler
Committee have lately proposed various
remedies. In the best of circumstances
the life of a marine boiler in constant
use cannot be relied upon to extend
over more than from eight to ten years.
^Besides the above sources of inefficiency,
the boilers of a ship occasionally fail
from insufficiency of steam space and
draught, from priming, or "foaming,"
as Mr. Shock prefers to call it, from the
coating of the tubes with soot, and from
a simple want of power to meet the de-
mands of the engines. On the whole,
the marine boiler is a costly and at
times an exceedingly troublesome charge
on board ship.

Mr. Shock does not confine himself to
the construction and management of
ships' boilers alone, but discusses the
whole complicated subject of steam gene-
rators. He devotes, however, the bulk
of his work to the consideration of the
marine boiler, and it must always tax the
ingenuity of the practical engineer more

than any other. As the writer observes,
the designing- of a boiler of this sort, and
more particularly for service in the Navy,
involves the fulfilment of conditions,
which are, to some extent, antagonistic.
Hence, compromises have to be accepted,
and many advantages with regard to
economic and potential efficiency have to
be sacrificed to other essential require-
ments. In the matter of tubes, for ex-
ample, the efficiency of their action as
heating surfaces, has been subordinated
to the necessity of increasing the draught.
In an ordinary boiler the principal condi-
tions to be satisfied in the design are
that it must be able to provide the nec-
essary amount of power, that its parts
must be arranged with regard to dura-
bility and economic .efficiency, and that
every portion must possess the required
strength. Boiler efficiency is commonly
defined to be the proportion borne by
the heat transmitted to the total quantity
of heat that would be yielded by the
complete combustion of the fuel. The
efficiency of the heating surface, on the
other hand, is the proportion borne by
the quantity of heat transmitted to the
water in the boiler to that available for
transmission. If, therefore, the combus-
tion could be made perfect, the efficiency
of the heating surface would be the effi-
ciency of the boiler. As this, however,
is not practicable, very elaborate meas-
ures are necessary to secure the largest
amount of efficiency. Thus the length
and width of the firegrate must be such
as will permit of the proper management
of the fire and of the cleaning of the
back and front corners ; the ashpit must
admit a sufficient quantity of air, moving
at a low velocity to every part of the
grate ; the furnace must afford ample
space for the gases to mingle thoroughly
and allow of the proper consumption of
the fuel; the combustion chamber must
be spacious enough to permit the g^ses
room and time to complete their combus-
tion before entering the tubes ; the heat-
ing surfaces require to be arranged in
such a way as to facilitate the escape of
steam from them as soon as formed ;
while the water spaces must not only be
strongly stayed, but must be designed
to admit of the free circulation of the
water and of the rapid formation of
steam on the furnace crown.

In the marine boiler, however, certain

THE MARINE BOILER.

501

limitations, which seriously fetter the
hands of the engineer, must be taken
into account The space available on

board is always circumscribed, and some-
times unnecessarily so. while the weight
of the boiler and its attachments and fit-
tings must be kept within the lowest
limits compatible with safety. There is
also the important difference that salt
water must l>e used, though the quantity,
Owing to the introduction of surface con-
densers, has been reduced to a minimum.
In a man-of-war, where it is especially
important that all parts of the machinery
and boilers should be placed as low as
possible, it is generally stipulated, in
spite of the protection which is now af-
forded by armor and wing bunkers, that
no part connected with the steam space
of the boilers shall protrude above the
r-line. Boilers are necessarily, there-
fore, placed in the narrowest parts of a
ship, with the result that they are greatly
cramped and confined. Hence defective
combustion, in consequence of the varia-
ble draught of the furnaces and the diffi-
culties of stoking, ensues. When ships
are entirely denuded of masts and are
made to depend entirely upon steam pro-
pulsion, more attention will probably be
given to the effective disposal of boilers.
Various methods have been adopted with
a view of improving the stiam arrange-
ments. Generally speaking, the rule was
to crowd the boilers of a man-of-war into
a single stokehold forward of the engines ;
but in the Mercury and Iris class they are
located in two stokeholds, separated from
each other and the engine-room by thwart-
ship bulkheads. It was also the custom
to place their ends close against the sides
of the ship and to stoke from the center ;
but in modem armor-clads the system
has been introduced of dividing the
boiler-room by a longitudinal water-tight
bulkhead and stoking from the wings.
This plan secures greater comfort for the
stokers and affords additional security for
the ship. In the Inflexible double-ended
boilers have been adopted, but they
seem to have dropped into their places
without any other purpose than that of
fining up a little spare room.

The types of marine boilers are very
numerous, apart altogether from the
grand distinctions of low and high press-
ure. Some have the tubes vertical and j
others horizontal ; some are fitted with

water tubes while in others the tubes

form the beating surfaces. Steel loco-
motive boilers, similar to those carried

by torpedo bouts, have been lately intro-
duced into the Polyphemus for the sake of

economy as regards space, combined

with extraordinary working pressures.

The result, so far, however, his not
been attended with complete success.

The boilers which are generally used in
Her Majesty's ships are of the horizontal
tubular type, with regard to which the
area of the firegrate is the principal
factor in determining the space to be
occupied by them in the length and
breadth of a vessel. The power of a
boiler is measured by the weight of
steam which it can generate in a unit of
time, and the working pressure varies
from 30 lbs. for simple engines, 60 lbs.
for compound engines, and 120 lbs, and
upwards on the square inch in the new
steel boilers which have been provided
for engines working at great rates of ex-
pansion. In low-pressure boilers of the
best kind, driven at full power, about
30 lbs. of coal is burnt per hour and 10
indicated horse-powers developed per
square foot of firegrate, while in high-
pressure boilers the amount of coal con-
sumed is 21 lbs. and the power developed
8.5 per square foot of grate. These are
the data adopted by Mr. Sennett in his
work on the marine steam engine ; but
Mr. Shock thinks it may be assumed for
general purposes that engines consume
from 20 lbs. to 30 lbs. of steam per in-
dicated horse-power per hour, the latter
quantity being consumed by engines
using saturated steam of about 35 lbs.
pressure above the atmosphere, with a
moderate rate of expansion, the cylinders
having no steam-jacket. The former
quantity is required for the best types
of engines using dry steam of from 60
lbs. to 80 lbs. pressure and working at a
high rate of expansion, the cylinders
being steam-jacketed. A marine boiler
of ordinary kind and proportions, using
natural draught, produces under these
conditions, with anthracite coal, from
3.5 to 5.5 indicated horse-powers per
square foot of grate, while with a free-
burning, semi-bituminous coal, it pro-
duces from 4.5 to 7.5 indicated horse-
powers per square foot.

Mr. Shock writes very cautiously and
vaguely on the subject of forced draught,

502

VAN nostrand's engineering magazine.

which is at present interesting English
engineers, and the advantages of which
are so assured, under certain conditions,
that it has been introduced into the
Polyphemus and the cruisers of the
Leander class, and is stipulated for in
the specifications for the Benbow and
the Camperdown, which are about to
be laid down. It is clear that the au-
thor has had no experience with reference
to its use. " With forced draught," he
observes, "as many as 10 indicated horse-
powers per square foot of grate have
been developed by several large English
naval vessels of recent construction, dur-
ing their full-power trials for six consecu-
tive hours at sea, by using from 25 lbs. to
30 lbs. of carefully-selected free-burning
coal per square foot of grate per hour."
But it is clear that Mr. Shock here refers
to the use of the steam blast, a method
of stimulating a sluggish draught which
the Admiralty do not approve and which
they desire shall be discontinued as much
as possible at official trials. In America
many experiments have been made with
the object of determining the benefit of
facilitating combustion by forcing air
directly under the grates by means of
fans. This method of increasing draught
is said to be very economical; but, as
the blast in this case must be delivered
with air-tight ashpit doors, the ventila-
tion of the stokehold is almost wholly
destroyed, and the stokers find the heat
and dust insupportable. In the system
of forced draught which is now being
gradually and somewhat timidly intro-
duced into the English navy the air is
delivered directly into the boiler-room,
which is enclosed by air tight bulkheads
and decks, and has no outlet for the air,
except through the grates. By this method
an increased barometric pressure is pro-
duced. The boilers are worked with
open ashpits, and the ventilation of the
boiler room is as perfect as with the
natural draught. There is. no doubt, a
certain amount of loss from leakage,
but this is scarcely appreciable, while
in closed ironclads, in which natural
draught must be always imperfect and vari-
able, the advantages are great and import-
ant. As has been already stated in these
columns, with the use of forced draught
there would not only be an abundance of
air delivered into the stokehold under all
conditions of wind and weather, but the

amount would be uniform and produce a
uniform head of steam. The amount of
pressure, also, would be adjustable to the
varying circumstances of the moment.
What, however, is particularly desiderat-
ed in a man-of-war is the combination of
alertness with powers of offence and de-
fence. It is of supreme importance that
it should possess what is termed " nim-
bleness,"— that is, a power in critical
emergencies of putting on a great spurt
on short notice ; adding a knot or two
to the regular full speed for a brief period,
or as long as a modern naval action is
likely to last. For this purpose forced
combustion must be depended upon.s
Superheaters are another subject on
which Mr. Shock writes with considera-
ble vagueness. In the American navy
the practice of using superheated steam
appears to be general, but in our own it
has been well-nigh discarded. Under
certain conditions it tends to increase
the dynamic efficiency of the engine and
produces economy in the consumption
of fuel; but much depends upon the
temperature of the saturated steam and
upon the rates of expansion due to the
cut-off. For general purposes the gain
is inconsiderable, and is counterbalanced
by the additional wear and tear, the
scoring of the cylinder which it causes,
the greater friction of the piston, and
the tighter packing which is neces-
sary to prevent waste. Superheaters
are accordingly getting out of favor even
when applied to low pressure boilers ;
while to the high pressure types they are
seldom fitted, because the greatest tem-
perature of steam that can be safely used
in ordinary marine engines appears to be
about 340 deg. to 350 deg. Fahrenheit,
so that there is very little margin for
superheating steam of 60 lbs. pressure and
upwards.

The specification for the construction
of boilers for the English navy are less
detailed than for those of the American
service. They are, nevertheless, suffi-
ciently comprehensive and stringent to
secure good material and workmanship.
All plates (with the exception of Low
Moor, Bowling, or Farnley plates, which
are not tested), must be capable of with-
standing a tensile strain of 21 tons per
square inch lengthwise and of 18 tons
crosswise, and a hot forge test of being bent
125 deg. lengthwise of the grain and 100

ill ( I BIC LIGHT I'.Y [NCANDE8< EN< l .

;><>:{

riu'v are also required to

:i Crucial cold foT| LDgle ami

other irons ami rivets used in their con-
struction must be also subjected to
similar ordeals. Each o{ the tubes are

to he proved by water pressure separately
up to 'MM) 11 square inch ; and it is

farther demanded that the maximum

strain on the BtajS at the working ]

-hall not exceed 5,000 lb. per square

inch tion at the bottom of the

thread. After the boiler has been con-
structed according to the specifications,
it is required to be tested by hydraulic
-ure up to double its working press-
Mr. shock treats at great length
of the deterioration of marine
boilers. His observations, however, are
91 part of too speculative and
theoretical a character to have much
cal value. Two Admiralty com-
mittees, presided over respectively by

Admiral Sir (it rg€ I'd i"< and .Mr. -lames

Wright, Engineer-in chief of the Navy,
have made boiler deterioration the sub

ject of long and patient experimental
inquiry, and both agree in Timlin-- that it

is principally due to the action of the air
having BCCeSS to the boilers when not
under steam, or being carried into them
with the feed when under s< earn. They also

consider that the greater deterioration in
tin4 boilers of the Royal Navy,as compared
with those <»f the mercantile marine, is

chiefly, if not entirely, owing to the fact
that Her Majesty's ships are necessarily
little under steam, and that their boilers
are thereby much more exposed to tin;
action of the moist air than those em-
ployed in the merchant service. The
regulations in the "Steam Manual'1 have
accordingly been modified and supple-
mented in accordance with their recom-
mendations.

ELECTRIC LIGHT BY INCANDESCENCE.*

By JOSEPH W. SWAN.

Spearing in this place on electric light,
I can neither forget nor forbear to men-
tion, as inseparablv associated with the
subject and with the Royal Institution,
the familiar, illustrious, names of Davy
and Faraday. It was in connection with
this institution that, eighty years ago, the
first electric light experiments were made
by Davy, and it was also in connection
with this Institution, that, forty years
later, the foundations of the methods, by
means of which electric lighting has been
made useful, were strongly laid by Far-
aday.

I d<> not propose to describe at any
length the method of Davy. I must, how-
ever, describe it slightly, if only to make
el ear the difference between it and the
newer method which I wish more particu-
larly to bring under your notice.

The method of Davy consists, as almost
all of you know, in producing electrically a

■♦.am of white-hot gas between two
pieces of carbon.

When electric light is produced in this
manner, the conditions which surround
the process are such as render it inrpossi-

* Lecture delivered at the Royal Institution of Great
Britain, March 10, 1882.

ble to obtain a small light with propor-
tionally small expenditure of power. In
order to sustain the arc in a state ap-
proaching stability, a high electromotive
force and a strong current are necessary ;
in fact, such electromotive force and such
current as correspond to the production
of a luminous center of at least several
hundred candle-power. When an at-
tempt is made to produce a smaller cen-
ter of light by the employment of a pro-
portionally small amount of electrical
energy, the mechanical difficulties of
maintaining a stable are, and the diminu-
tion in the amount of light (far beyond
the diminished power employed), puts a
a stop to reduction at a point at which
much too large a light is produced for
common purposes.

The often-repeated question, "Will
electricity supersede gas ?" could be
promptly answered if we were confined
to this method of producing electric
light ; and for the simple reason that it
is impossible, by this method, to produce
individual lights of moderate power.

The electric arc does very well for street
lighting, as you all know from what is
to be seen in the city. It also does very

504

VAN NOSTKAND'S ENGINEEKI^G MAGAZINE.

well for the illumination of such large
inclosed spaces as railway stations ; but
it is totallly unsuited for domestic light-
ing, and for nine-tenths of the other pur-
poses for which artificial light is required.
If electricity is to compete successfully
with gas in the general field of artificial
lighting, it is necessary to find some
other means of obtaining light through
its agency than that with which we have
hitherto been familiar. Our hope centers
in the method — I will not say, the new
method — but the method which until
within the last few years has not been
applied with entire success, but which,
within a recent period, has been rendered
perfectly practicable — I mean the method
of producing light by electrical incan-
descence.

The fate of electricity as an agent for
production of artificial light in substitu-
tion for gas, depends greatly on the suc-
cess or non-success of this method ; for
it is the only one yet discovered which
adapts itself with anything like complete-
ness to all purposes for which artificial
light is required.

If we are able to produce light economi-
cally through the medium of electrical
incandescence, in smaJJ quantities, or in
large quantities, as it may be required,
and at a cost not exceeding the cost
of the same amount of gas-light, then
there can be little doubt — there can,
I think, be no doubt — that in such a
form, electric light has a great future
before it. I propose, therefore, to ex-
plain the principle of this method of
lighting by incandescence to show how it
can be applied, and to discuss the ques-
tion of its cost.

When an electrical current traverses a
conducting wire, a certain amount of re-
sistance is opposed to the passage of the
current. One of the effects of this con-
flict of forces is the development of heat.
The amount of heat so developed de-
pends on the nature of the wire — on its
length and thickness, and on the strength
of the current which it carries. If the
wire be thin and the current strong, the
heat developed in it may be so great as
to raise it to a white heat.

The experiment I have just shown il-
lustrates the principle of electric lighting
by incandescence, which is briefly this —
that a state of white heat may be pro-
duced in a continuous solid conductor

by passing a sufficiently strong electrical
current through it.

A principle, the importance of which
cannot well be over estimated, underlies
this method of producing light electri-
cally— namely, the principle of divisibil-
ity. By means of electric incandescence
it is possible to produce exceedingly
small centers of light, even so small a&
the light of a single candle ; and with no
greater expenditure of power in propor-
tion to the light produced, than is in-
volved in the maintenance of light-cen-
ters 10 or 100 times greater. Given a
certain kind of wire, for example a plati-
num wire, the 100th of an inch in diame-
ter, a certain quantity of current would
make this wire white-hot whatever its
length. If in one case the wire were
one inch long and in another case ten
inches long, the same current passing
through these two pieces of similar wire,
would heat both to precisely the same
temperature. But in order to force the
same current through the ten times
longer piece, ten times the electro-motive-
force, or, if I may be allowed the expres-
sion, electrical pressure, is required, and
exactly ten times the amount of energy
would be expended in producing this in-
creased electro-motive force.

Considering, therefore, the proportion
between power applied and light pro-
duced, there is neither gain nor loss in
heating these different lengths of wire.
In the case of the longer wire, as it had
ten times the extent of surface, ten times>
more light was radiated from it than
from the shorter wire, and that is exactly
equivalent to the proportional amount of
power absorbed. It is therefore evident
that vjhether a short piece of wire or a
long piece is electrically heated, the
amount of light produced is exactly
proportional to the poioer expended in
producing it.

This is extremely important ; for not
only does it make it possible to produce
a small light where a small light is re-
quired, without having to pay for it at a
higher rate than for a larger light, but it
gives also the great advantage of obtain-
ing equal distribution of light. As the
illuminating effect of light is inversely as
the square of the distance of its source,
it follows that where a large space is to-
be lighted, if the lighting is accomplished
by means of centers of light of great

ELECTRIC LIGHT Bl tNCAND U I .

505

power, a much larger total quantity of

light h;is

to be employed in order to
spaces remotest from these

make the

centers sufficiently Light, than would be
required if the illumination of the Bpace
obtained by numerous smaller
lights equally distributed.

In order to practically apply the prin-

ciple of producing light by the incandes-
cence <>( an electrically heated continu-
ous solid conductor, it is necessary to
•t for the light-giving body a material

which offers a considerable resistan<
the J of the electric current, and

which is also capable of bearing an ex-
ceedingly high temperature without lin-
ing fusion or other change.
an illustration of the difference that

exists among different substances in

re-

to the flow of au elec-
tric current, and consequent tendency to
me heated in the act of electrical
transmission, here is a wire formed in
alternate sections of platinum and silver;
the wire is perfectly uniform in diameter,
and when I pass an electric current
through it, although the current is uni-
form in every part, yet, as you see, the
wire is not uniformly hot, but white-hot
only in parts. The white-hot sections
are platinum, the dark sections are silver.
Platinum offers a higher degree of resist-
ance to the passage of the electric cur-
rent than silver, and in consequence of
this, more heat is developed in the plati-
num than in the silver sections.

The high electrical resistance of plati-
num, and its high melting-point, mark it
out as one of the most likely of the
metals to be useful in the construction
of incandescent lamps. When platinum
is mixed with 10 or 20 per cent, of iri-
dium, an alloy is formed, which has a
much higher melting-point than plati-
num ; and many attempts have been
made to employ this alloy in electric
lamps. But these attempts have not
been successful, chiefly because, high as
is the melting-point of iridio-platinum,
it is not high enough to allow of its
being heated to a degree that would
yield a sufficiently large return in light for
energy expended. Before an economical
temperature is reached, iridio-platinum
ware slowly volatilizes and breaks. This
is a fatal fault, because in obtaining
light by incandescence there is the great-
est imaginable advantage in being able
Vol. XXVII— No. 6—35.

to heat tin incandescing body to an ex-
tremely high temperature. 1 will illus-
t rate t his by experiment.

Here is a ^lass bulb containing a fila-
ment of carbon. When I pass through

the filament one unit of current, light
equal tottoo candles is produced. If now

I increase the current bjone half, making
it One unit ((ikI a half, the limit is in
creased to thirty candles, or thereabout,

so that for this one-half increase of cur-
rent (which involves nearly a doubling OJ
'//' <nergye\^)vm\ii(\),Jifteeit times more
light is produced.

It will readily be understood from
what I have shown that it is essential to
economy that the incandescing material
should be able to bear an enormous
temperature without fusion. We know
of no metal that fulfils this requirement;
but there is a non-metallic substance
which does so in an eminent degree,
and which also possesses another quality,
that of loio conductivity. The substance
is carbon. In attempting to utilize car-
bon for the purpose in question, there
are several serious practical difficulties
to be overcome. There is, in the first
place, the mechanical difficulty arising
from its intractability. Carbon, as we
commonly know it, is a brittle and non-
elastic substance, possessing neither duc-
tility nor plasticity to favor its being
shaped suitaby for use in an electric
lamp. Yet, in order to render it service-
able for this purpose, it is necessary to
form it into a slender filament, which
must possess sufficient strength and
elasticity to allow of its being firmly at-
tached to conducting wires, and to pre-
vent its breaking. If heated white hot
in the air, carbon burns away ; and there-
fore means must be found for prevent-
ing its combustion. It must either be
placed in an atmosphere of some inert
gas or in a vacuum.

During the last forty years, sjmsmodic
efforts have from time to time been made
to grapple with the many difficulties
which surround the use of carbon as the
wick of an electric lamp. It is only
within the last three or four years that
these difficulties can be said to have been
surmounted. It is now found that car-
bon can be produced in the form of
straight or bent filaments of extreme
thickness, and possessing a great degree
of elasticity and strength. Such fila-

506

VAN NOSTRAND'S ENGINEERING MAGAZINE.

ments can be produced in various ways —
by the carbonization of paper, thread,
and fibrous woods and grasses. Excel-
lent carbon filaments can be produced
from the bamboo, and also from cotton
thread treated with sulphuric acid. The
sulphuric acid treatment effects a change
in the cotton thread similar to that
which is effected in paper in the process
of making parchment paper. In carbon-
izing these materials, it is of course nec-
essary to preserve them from contact
with the air. This is done by surround-
ing them with charcoal.

Here is an example of a carbon fila-
ment produced from parchmentized cot-
ton thread. The filament is not more
than the .01 of an inch in diameter, and
yet a length of three inches, having
therefore a surface of nearly the one-
tenth of an inch, gives a light of twenty
candles when made incandescent to a
moderate degree.

I have said, that, in order to preserve
these slender carbon filaments from com-
bustion, they must be placed in a
vacuum ; and experience has shown that
if the filaments are to be durable, the
vacuum must be exceptionally good.
One of the chief causes of failure of the
earlier attempts to utilize the incandes-
cence of carbon, was the imperfection of
the vacua in which the white-hot fila-
ments were placed ; and the success
which has recently been obtained is in
great measure due to the production of a
better vacuum in the lamps.

In the primitive lamps, the glass shade
or globe which inclosed the carbon fila-
ment was large, and usually had screw
joints, with leather or india-rubber wash-
ers. The vacuum was made either by
filling the lamp with mercury, and then
running the mercury out so as to leave a
vacuum like that at the upper end of a
barometer, or the air was exhausted by
a common air pump. The invention of
the mercury pump by Dr. Sprengel, and
the publication of the delicate and beauti-
ful experiments of Mr. Crookes in con-
nection with the radiometer, revealed
the conditions under which a really high
vacuum could be produced, and in fact
gave quite a new meaning to the word
vacuum. It was evident that the old in-
candescent lamp experiments had not
been made under suitable conditions as

to vacuum ; and that before condemning
the use of carbon, its durability in a
really high vacuum required still to be
tested. This idea having occurred to
me, I communicated it to Mr. Stearn,
who was working on the subject of high
vacua, and asked his co-operation in a
course of experiments having for their
object to ascertain whether a carbon
filament produced by the carbonization
of paper, and made incandescent in a
high vacuum was durable. After much
experimenting we arrived at the con-
clusion that when a well formed carbon
filament is firmly connected loith con-
ducting ivires, and placed in a hermeti-
cally sealed glass ball perfectly exhausted,
the filament suffers no apparent change
even when heated to an extreme degree of
whiteness. This result was reached in
1878. It has since then become clearly
evident that Mr. Edison had the same
idea and reached the same conclusion as
Mr. Stearn and myself.

A necessary condition of the higher
vacuum was the simplification of the
lamp. In its construction there must be
as little as possible of any material, and
there must be none of such material as
could occlude gas, which being eventually
given out would spoil the vacuum.
There must besides be no joints except
those made by the glass-blower.

Therefore, naturally and per force of
circumstances, the incandescent carbon
lamp took the most elementary form, re-
solving itself into a simple bulb, pierced
by two platinum wires supporting a fila-
ment of carbon. Probably the first
lamp, having this elementary character,
ever publicly exhibited, was shown in
operation at a meeting of the Literary
and Philosophical Society of Newcastle
in February, 1879. The vacuum had
been produced by Mr. Stearn by means
of an approved Sprengel pump of his
invention.

Blackening of the lamp glass, and
speedy breaking of the carbons, had been
such invariable accompaniments of the
old conditions of imperfect vacua, and of
imperfect contact between carbon and
conducting wires, as to have led to the
conclusion that the carbon was volatilized.
But under the new conditions these faults
entirely disappeared ; and carefully con-
ducted experiments have shown that

ELECTRIC LKiHT BY INCANIHX 1 :\< I .

f>07

well-made lumps arc quite serviceable

after more than a thousand hours' con-
tinual cue

Here are sonic specimens of the la
and most perfected forms of lamp. The
mode of attaching the filament to the
conducting wires by means of a tiny tube
of platinum, ami als-> tic improved form
of the lamp, arc due to the skill of Mr.
Gmimingham.

The lamp ily attached and de-

tached from the socket which connects it
with the conducting wires j and can be
adapted to a great variety of fittings, and
these may be provided with switches or
for lighting or extinguishing the
lamps. I have here a lamp fitted espe-
cially for use in miues. The current may
be supplied either through main wires
from a dynamo-electrical machine, with
flexible branch wires to the lamp, or it
be fed by a set of portable store
cells closely connected with it. I will
give you an illustration of the quality of
the light these incandescent lamps are
capable of producing by turning the cur-
rent from a Siemen's dynamo-electric
machine (which is working by means of
a gas engine in the basement of the build-
ing) through sixty lamps ranged round
the front of the gallery and through six
on the table. (The theater was now com-
pletely illuminated by means of the lamps,
the gas being turned off during the rest
of the lecture.)

It is evident by the appearance of the
flowers on the table that colors are seen
very truly by this light, and this is sug-
gestive of its suitability for the lighting
of pictures.

The heat produced is comparatively
very small ; and of course there are no
noxious vapors.

And now I may, I think, fairly say that
the difficulties encountered in the con-
struction of incandescent electric lamps
have been completely conquered, and
that their use is economically practicable.
In making this statement I mean, that,
both as regards the cost of the lamp itself
and the cost of supplying electricity to
ill a mi ndte it, light can be produced at a
cost which will compare not unfavorably
with the cost of gas light. It is evident
that if this opinion can be sustained,
lighting by electricity at once assumes a
position of the widest public interest,
and of the greatest economic importance;

and iii view of this, I may be permitted
to enter with some detail into aconsid.
ation of the facts which support it.

There has now been sntlicient experi-
ence in the manufacture of lamps to lea

no doubt that they can be cheaply con-
structed, and we know by actual experi-
ment that continuous heating to a fairly
high degree of incandescence during 1,200

hours does not destroy a well-made lamp.
What the utmost limit of a lamp's life
may be we really do not know. Prob-
ably it will be an ever-increasing span ;

as, with increasing experience, processes
of manufacture are sure to become more
and more perfect. Taking it, therefore,
as fully established that a cheap and
durable lamp can now be made, the fur-
ther question is as to the cost of the means
of its illumination.

This question in its simplest form is
that of the more or less economical use
of coal ; for coal is the principally raw
material alike in the production of gas
and of electric light. In the one case,
the coal is consumed in producing gas
which is burnt ; in the bther in produc-
ing motive power, and, by its means,
electricity.

The cost of producing light by means
of electric incandescence may be com-

! pared with the cost of producing gas-
light in this way — 2 cwt. of coal produces
1,000 cubic feet of gas, and this quantity
of gas, of the quality called fifteen-candle
gas, will produce 3,000 candle-light for
one hour. But besides the product of

! gas, the coal yields certain by-products
of almost equal value. I will, therefore,
take it that we have in effect 1,000 feet

; of gas from 1 cwt. of coal instead of
from 2, as is actually the case.

And now, as regards the production of

j electricity. One cwt. of coal — that is
the same measure in jyoint of value as
gives 1,000 feet of gas — will give 50
horse-power for one hour. Repeated
and reliable experiments show that we
can obtain through the medium of incan-
descent* lamps at least 200 candle-light
per horse-power per hour. But as there
is waste in the conversion of motive
power into electricity, and also in the
conducting-wires, let us make a liberal
deduction of 25 per cent., and take only
150 candle-light as the net available pro-
duct of 1 horse-power; then for50horse-

I po wer (the product of 1 cwt. of coal), we

508

van nostrand's engineering magazine.

have 7,500 candle-light, as against 3,000
candle-light from an equivalent value of
gas. That is to say two and a half times
more light.

There still remains an allowance to be
made to cover the cost of the renewal of
lamps. There is a parallel expense in
connection with gas lighting in the cost
of the renewal of gas-burners, gas globes,
gas chimneys, &c. I cannot say that I
think these charges against gas-lighting
will equal the corresponding charges
against electric-lighting, unless we im-
port into the account — as I think it right
to do — the consideration that, without
a good deal of expense be incurred in
the renewal of burners, and unless mi-
nute attention be given, far beyond what
is actually given, to all the conditions
under which the gas is burned, nothing
like the full light product which I have al-
lowed to be obtainable from the burning
of 1,000 cubic feet of gas, will be obtained,
and, as a matter of fact, is not commonly
obtained, especially in domestic lighting.
Taking this into account, and consider-
ing what would have to be done to ob-
tain the full yield of light from gas, and
that if it be not done, then the estimate
I have made is too favorable, I think but
little, if any, greater allowance need be
made for the charge in connection with
the renewal of lamps in electric lighting
than ought to be made for the corre-
sponding charges for the renewal of gas
burners, globes, chimneys, &c. But it
will be seen that even if the cost for re-
newal of lamps should prove to be con-
siderably greater than the corresponding-
expense in the case of gas, there is a wide
margin to meet them before we have
reached the limit of the cost of gas-light-
ing.

I think too it must be fairly taken into
account and placed to the credit of elec-
tric lighting, that by this mode of light-
ing there is entire avoidance of the dam-
age to furnishings and decorations of
houses, to books, pictures, and to goods
in shops, which is caused through light-
ing by gas, and which entails a large ex-
penditure for repair, and a large amount
of loss which is irreparable.

I have based these computations of
cost of electric light on the supposition
that the light product of 1 horse-power
is 150 candles. But if durability of the
lamps had not to be considered, and it

were an abstract question how much
light can be obtained through the medi-
um of an incandescent filament of car-
bon, then one might, without deviating
from ascertained fact, have spoken of a
very much larger amount of light as ob-
tainable by this expenditure of motive
power. I might have assumed double or
even more than double the light for this
expenditure. Certainly double and treble
the result I have supposed can actually
be obtained. The figures I have taken
are those which consist with long life to
the lamps. If we take more light for a
given expenditure of power, we shall
have to renew the lamps oftener, and so
what we gain in one way we lose in
another. But it is extremely probable
that a higher degree of incandescence
than that on which I have based my cal-
culations of cost, may prove to be com-
patible with durability of the lamps. In
that case, the economy of electric light-
ing will be greater than I have stated.

In comparing the cost of producing
light by gas and by electricity, I have
only dealt with the radical item of coal
in both cases. Gas-lighting is entirely
dependent upon coal — electric lighting
is not, but in all probability coal will be
the chief source of energy in the electric
lighting also. When, however, water
power is available, electric lighting is in
a position of still greater advantage, and,
in point of cost, altogether beyond com-
parison with other means of producing
light.

To complete the comparison between
the cost of electric light and gas light,
we must consider not only the amount of
coal required to yield a certain product
of light in the one case and in the other,
but also the cost of converting the coal
into electric current and into gas ; that is
to say, the cost of manufacture of elec-
tricity and the cost of manufacture of
gas. I cannot speak with the same ex-
actness of detail on this point as I did on
the comparative cost of the raw material.
But if you consider the nature of the
process of gas manufacture, and that it is
a process, in so far as the lifting of coal
by manual labor is concerned, not very
unlike the stoking of a steam boiler, and
if electricity is generated by means of
steam, then the manual labor chiefly in-
volved in both processes is not unlike.
It is evident that in gas manufacture it

ELECTRIC LIGHT r.Y INcandkm I \< I .

609

ulcl be necessary to shovel into the
furnaces and retorts five or six times as
much coal to yield the same light pro-
duel as would l>e obtainable through the

mi engine and incandescent lamps.
Bui In iv to allow for

the value of the labor in connection with
the products other than gas, and hence it

right to cut down the difference I have
mentioned to half — /.<■., debit gas with
only half the cost of manufacture, in the

Bame way as in our calculation we have
charged gas with only one-half the coal
actually used. But when that is done
tin still a difference of probably

three to one in respect of labor in favor
of electric lighting.

I have ma 36 large allowances of

material and labor in favor of the cost of

3, but it is well known that the bye
products are but rarely of the value I
have assumed. I desire, however, to al-
all that can be claimed for gas.

With regard to the cost of plant, I
think there will be a more even balance in
the two cases. In a gasworks you have
retorts and furnaces, purifying chambers
and gasometers, engines, boilers, and
appliances for distributing the gas and
regulating its pressure. Plant for gen-
erating electricity on a large scale would
si principally of boilers, steam en-
gines, dynamo-electric machines, and
Series for storage.

No such electrical station, on the scale
and in the complete form I am supposing,
has yet been put into actual operation ;
but several small stations for the manufac-
ture of electricity already exist in Eng-
land, and a large station designed by Mr.
Edison, is, if I am rightly informed, al-
most completed in America. We are
therefore on the point of ascertaining by
actual experience, what the cost of the
works for generating electricity will be.
Meanwhile, we know precisely the cost of
boilers and engines, and we know ap-
proximately what ought to be the cost of
dynamo-electric machines of suitably
large size. We have, therefore, sufficient
grounds for concluding that to produce a
given quantity of light electrically the
cost of plant would not exceed greatly, if
at all, the cost of equivalent gas-plant.

There remains to be considered, in con-
nection with this part of the subject, the
cost of distribution. Can electricity be
distributed as widely and cheaply as gas?

On one condition, which I fully hope
can be Complied with, this may be an-
swered in the affirmative. The condi-
tion is that it. may be found practicable
and safe to distribute electricity <>f com-
paratively high tension.

The importance of this condition will
be understood when it is remembered
that, to effectively Utilize electricity in the
production of light in the manner J have
been explaining, it is necessary that the
resistance in the c<irl><>n of the lamps
should be relatively great to the resist-
(nice in the wires which convey the cur-
rent to them. When lamps are so united
with the conducting wire, that the cur-
rent which it conveys is divided amongst
them, you have a condition of things in
which the aggregate resistance of the
lamps will be very small, and the con-
ducting wire, to have a relatively small
resistance, must either be very short, or,
if it be long, it must be very thick, other-
wise there will be excessive waste of en-
ergy ; in fact, it will not be a practical

! condition of things.

In order to supply the current to the
lamps economically, there should be com-
paratively little resistance in the line. A
waste of energy through the resistance of
the wire of 10 or perhaps 20 per cent,
might be allowable, but if the current is

| supplied to the lamps in the manner I
have described — that of multiple arc, each
lamp being as it were a <-rossing between
two main wires, then — and even if the
individual lamps ofiered a somewhat
higher degree of resistance than the lamps
now in actual use — the thickness of the
conductor would become excessive if the
line was far extended. In a line of half a
mile, for instance, the weight of copper
in the conductor would become so great,

I in proportion to the number of lamps
supplied through it, as to be a serious

; charge on the light. On the other hand,

i if a smaller conducting wire were used.

i the waste of energy and consequent cost

! would greatly exceed that 1 have men-

1 tioned as the permissive limit.

Distribution in this manner has the
merit of simplicity, it involves no danger
to life from accidental shock ; and it does
not demand great care in the insulation of
the conductor. But it has the great de-
fect of limiting within comparatively
small bounds the area over which the
power for lighting could be distributed

510

VAN NOSTEAND'fe ENGHSTEEKING MAGAZINE.

from one center. In order to light a
large town electrically on this system, it
would be necessary to have a number of
supply stations, perhaps half a mile or a
mile apart. It is evidently desirable to be
able to effect a wider distribution than
this, and I hope that either by arranging
the lamps in series, so that the same
current passes through several lamps
in succession, or by means of second-
ary voltaic cells, placed as electric reser-
voirs in each house, it may be possible
to economically obtain a much wider dis-
tribution.

"Whether by the method of multiple arc
which necessitates the multiplication of
electrical stations; or by means of the
simple series, or by means of secondary
batteries connected with each other from
house to house in siDgle series, the lamps
being fed from these in multiple arc, I am
quite satisfied that comparatively with the
distribution of gas, the distribution of
electricity is sufficiently economical to
permit of its practical application on a
large scale.

As to the cost of laying wires in a
house, I have it on the authority of Sir
Wm. Thomson, who has just had his
house completely fitted with incandescent
lamps from attics to cellars — to the en-
tire banishment of gas — that the cost of
internal wires for the electric lamps is less

than the cost of plumbing in connection
with gas-pipes.

I have expended an amount of time on
the question of cost which I fear must
have been tedious ; but I have done so
from the conviction that the practical in-
terest of the matter depends on this
point. If electric lighting by incandes-
cence is not an economical process, it is
unimportant ; but if it can be established
— and I have no doubt that it can — that
this mode of producing light is economi-
( al,the subject assumes an aspect of the
greatest importance.

Although at the present moment there
may be deficiencies in the apparatus for
generating and storing electricity on a
very large scale, and but little experience
in distributing it for lighting purposes
over wide areas, and consequently much
yet to be learnt in these respects ; yet, if
once it can be clearly established that,
light for light, electricity is as cheap as
gas, and that it can be made applicable
to all the purposes for which artificial
light is required, electric light possesses
such marked advantages in connection
with health, with the preservation of
property, and in respect of safety, as to
leave it as nearly certain as anything in
this world can be, that the wide substitu-
tion of the one form of light for the other
is only a question of time.

THE WEIGHTS OF FRAMED GIRDERS AND ROOFS.

• By JOSEPH HAYWOOD WATSON BUCK, M. Inst. C.E.

From Selected Papers of the Institution of Civil Engineers.

The attention of the author having
been lately directed to various formulae
for obtaining the approximate weight of a
girder or roof principal, he now proposes
first to ascertain the limiting spans de-
duced therefrom, taking the same type in
each case as the best means of compari
son, and afterwards to suggest the appli-
cation of general rules, which, he believes,
would prove of great service in design-
ing structures of this character, especially
in saving time, while ensuring results as
accurate as those obtained by the more
laborious processes in general use.

With this view he will first observe
that the weight of any bridging structure
of which the weight is equally distributed,

and which carries a fixed distributed
load, is given by the following series :

Let W=the external load,
and W Q^the weight of a girder of the
proposed type, of the strength re-
quired to carry W, but not its own
weight in addition.

Then Wx(Q + Q2 + Q3 &c, ad infinitum).
=the weight of such a girder of the
strength required to carry W and its
own weight in addition.

But the sum of this series =- — 77

1-Q'

Therefore- — pr^the total weight of the
J- — ^c
girder.

THE WEIGHTS OF FRAMED GIRDER8 \M> BOOF8.

511

Or, if

then

=the total weight of the

girder.

And the limiting span is reached when
, when a=W, the sum of the
a being then infinity.
In a paper on the reconstruction of the
Malahide Viaduct, Mi. \Y. Anderson, M.
Inst. C.E., furnishes the following rule
for roughly estimating the weight of a
latt der of uniform strength, de-

duced from the distribution of the mate-
in the girders used in that structure,
which are of 52 feet span, the strain per
lire inch of the gross section of the

booms beiug 4 tons, and the depth —^~

the span.

ght in lbs. ) ( Three times the
lineal foot > = •< distributed load
of girder. ) ( in tons.

Let \V = the external load,
and L = the span.
Reducing to tons.

— =the weight of the girder in

2.240 747 b &

tt'US.

This estimate does not include the

weight of the girder itself, but corre-

■nds to <i in the previous formula. Com-

pleting the series and reducing ..- =

the total weight of the girder, and the
limiting span is therefore 747 feet.

Professor Unwin, M. Inst. C.E.. in his
work "Iron Bridges and Roofs," gives
the formula,

WL/-
Cs-L

= the weight of the girder,

' and the limiting span is 589 feet.
Dod — L

The rule laid down by Mr. Benjamin
Baker, M. Inst, C.E., in his "Long-span

Railway Bridges,'1 is Wx ; t being

the strain in owts. per Bquare inch due to

the weight of the girder itself, and T the

strain in cwts. per Bquare inch due to the
entire load. His formula for the value of

t in a lattice girder is.

1'/

in which d is the depth in feet at the cen-
ter, and .'• and y are coefficients depend-
ing upon the practical construction of the
flange and web respectively, x being 0.03
and //being 2.7 + 0-001 L.

Inserting the value of t found by this
formula for the case of a girder the depth

of which is^-^ of the span, and reducing

12. o
the following quadratic equation is arrived
at: —

Q = 0.000001875 LJ + 0.001623 L.

Let Q = l.

Then L = 417 feet, the limiting span.

For comparison with these results, it is
now proposed to find a rule for the weight
and limiting span of a lattice girder whose

depth is —jr- of the span, as before, by

12. o
means of an application of the formula at
the commencement of this paper, using
the data supplied by the weight of one of
the girders of the Charing Cross bridge,
with its load and span, as stated by Mr.
B. B. Stoney, M. Inst.C.E.,in his "Theo-
ry of Strains."
Let the weight of any girder =g, its span
= /, and the external load = /c.

C being a coefficient depending on the
description of girder, r the ratio of depth
to span, and s the strain in tons per
squire inch of the gross section of the
booms.

For the Charing Cross bridge the value
of C assigned by Professor Unwin is 1,880,
and the depth measured between the cen-
ters of gravity of the booms is-^-. of the
J 12.8

span, as before. Therefore, if the strain
s be again taken as 4 tons per square
inch, the formula after reduction becomes

Then - -y • =//, whence Qfor the span /=

— — ; Q for any other span L = — ^— — r. ;

! ic + 7 , WL

I the limiting span S = /, and uZTf~ =

i the weight of any other girder of the same
! proportions carrying any load W.

Also, when the external load is propor-
tional to the span, as in the case of most
bridges, and of roofs having principals the
same distance apart in each instance ; if

512

VAN nostrand's engineering magazine.

G=the weight of any other girder, &c, of

the same proportions, G=tt: — =r-j.

(S — Li)0

The following details are quoted by
Mr. Stoney : — Weight of girder, deduct-
ing end pillars, 184 tons ; load on girder,
553.33 tons, exclusive of cornice, hand-
rail, fish-plates, bolts, spikes, chairs for
rails, hoopiron tongue and bolts for
planking, and ballast. Span of girder,
154 feet. Calling the total external load
640 tons,

^640 + 184
k 184~

X154

688-L

the weight of any other girder of the
same proportion carrying any load W, and
the limiting span is 688 feet (the weight
here found is that between bearings only).

0 Limiting Span.

Feet.

Anderson (Malahide Viaduct) 747

Buck (Charinir Cross Bridge) 688
Unwin ( " " ) 589
Baker 417

Now, however useful such formulae may
be for the purpose of rough estimation,
and for affording an approximate weight
upon which to base, in the first instance,
the calculations for a bridge or roof, there
can be no doubt that, when the span is
considerable, a great deal of time is
usually consumed in afterwards so adjust-
ing the final weight of the structure, that
the strains per square inch shall neither
exceed nor fall below the limiting strains ;
their scope also is necessarily very re-
stricted. A system seems therefore "to be
called for by which, during the process of
designing the structure, it may acquire,
by successive accretions, due strength in
each of its members ; and, after, a short
reference to the formula of Professor
Rankine, for use in designing girders, the
objections to which will be pointed out,
the author proposes to describe a system
which appears to fulfil the desired end.

Professor Rankine's formula, upon
which he bases the proportions of each
part of the girder, stands thus:

B'a.W

s/W'-^B"

W being the external working load, 5, its
factor of safety, s2 a factor of safety
suited to a steady load, B' the weight of

the girder as computed by considering
the breaking load alone, sl W ; and B
the total weight of the girder.

The whole of the external load is here
considered as a moving load, the only
fixed load being that of the girder itself.
Now, in the first place it is certain that in
a large bridge a great part of the load is
fixed, and secondly, the moving load can-
not be considered as provided for merely
by the use of a factor of safety, the ma-
terial introduced to meet the require-
ments of the moving load being distrib-
uted differently to that necessary for the
fixed load. In fact, such a procedure is
not applicable to open girders of any
kind.

The method proposed by the author
for proportioning the different members
of a framed girder, or roof principal, of
any materials, is based upon the follow-
ing considerations :

Let the fixed distributed load= W, and
WQ=a, as before.

Then, as before, ~ =the total weight

\V — a

of a girder of the strength required
to carry W, and its own weight in
addition.
Let b = the weight of the additional mate-
rial necessary to enable the girder to
carry the moving load, but not the
weight b in addition.

Then, by proportion, ^-=— = the

weight of a girder of the strength

required to carry W + b, and its own

weight in addition.
There still remains the increment b,
hitherto only considered as part of the
fixed load, which must be retained to sup-
port the moving load.
Therefore the total weight of the girder

becomes

W-a +°; ° W-a-\

considered for practical purposes as con-
sisting of the following elements :

W + b

)+*,

or c being the weight of a girder of the
strength required to carry W + b, but not
its own weight in addition ; and equal to

(W + b)a

ON \vi:vi:\lill'> FORMULAS FOB THE STBENGTB OF ICAtEBIALS. 519

-A- — -— + 6= the total weight of the

(W + />)-c

girder; consisting of the following ele-
ments,

l'*(W+»)-«r*
The application is as follows :

WHEN THXBJ i- WO MOVING LOAD.

I Find the dimensions of each part

of a girder of the Btrength required to

carrv the fixed load W, but not its own

ight in addition, and note the sectional

art ch member. Let the weight of

ler==a.

Multiply the sectional area of

each member by

WHF.N THKRE IS A MOVING LOAD OR WIND

PBB88UBI ACTING LONGITUDINALLY, AS IN

TH1 OF A ROOF PRINCIPAL.

For Large Structures.

i l.i Find the dimensions of each part
of a girder of the strength required to
carry the fixed load W (including, in a
bridge, its proportion of the floor, lateral
bracing, rails. &c), but not its own
weight m addition, and note the sectional
area of each member. Let the wreight of
this girder = a.

Multiply the sectional area of each

member by == (this step being taken

at once, in some cases reduces the addi-
tional material for stiffening the struts
accruing from the next steps).

(3.) Find the additional materia] re
quired in each member to enable the gir-
der to carry the moving load (in a root' to

!st the action of the wind), and also

in any new members which may be re-
quired for the same purpose, and note the
sectional area of each member. Lei the

total weight of this additional material =5
(not to be added).

(4.1 Multiply the sectional area of

every member, except the new ones, by
W + />

~W~" -

5. Add the additional material found
in (3), assigning to each member the in-
crement of sectional area due to it, and
inserting the new members, if any.

For Small Structures.

(1). Find the dimensions of each part
of a girder of the strength required to
carry the moving load, but not its own
weight in addition, and note the sectional
area of each member. Let the weight of
this girder = A (merely note this).

(2.) Find the dimensions of each part
of a girder of the strength required to
carry W + (5», but not its own weight in ad-
dition. Let the weight of this girder
= c.

(3.) Multiply the sectional area of each

member as found in (2) by -==- — — .

v ' J (W + A)— c

(4.) Add the material found in (1) al-
lotting to each member the increment of
sectional area due to it. If (1) has more
members than (2), insert the additional
members.

ON WEYRAUCH'S FORMULAS FOR THE STRENGTH

OF MATERIALS.

By II. TBE80A.

Translated from R6eam6 de la Soctete* des Ingenieurs Civils, Paris, for Abstracts of Institution of

civil Engineers.

The question was primarily whether
the known results of experiments up to
the present time, considered together,
were more correctly represented by the
formulas used in France or by those
proposed by recent German writers
This question was much simplified by
recognition of one main point of differ-
ence in the practice of the two countries.
It was the custom in France, in all ex-

periments on the

strength

materials)

to determine not only the breaking
strength, but also the limit of elasticity
and the elongations which corresponded
to those two critical conditions ; and the
limits of working stress were based upon
the limit of elasticity. In Germany, on
the contrary, the recent tendency had
been to fix working stresses with regard
to the breaking strength of the material.

514

VAN NOSTRAND'S ENGINEERING MAGAZINE.

Factors of safety, regulated by experi-
ence, were used by both parties.

It would seem that the limit of elastic-
ity was the more rational basis for cal-
culations, since it was more nearly allied
to the actual working conditions of the
material. Little difference, however,
existed between the limits of working
stress in common use, whatever the
standard of reference. It would suffice
for the purpose of discussion to examine
that part of Dr. Weyrauch's paper which
related to extension and compression
alone. His method depended solely up-
on the breaking strength of the material,
and ignored entirely the limit of elastic-
ity. It did not seem reasonable, how-
ever, to consider one alone of the differ-
ent properties of the material, whether
that one was the breaking strength or
the limit of elasticity. A close connec-
tion existed between both those elements
of the question, and it remained to be
seen whether the German formulas ga^e
due weight to that consideration.

In Weyrauch's notation, a represented j
the intensity, or amount per unit area
of section, of the " ultimate working
strength," that was the breaking strength
of the material under any given condi-
tions, x, y, z, representing the circum-
stances in which the material worked,
of which conditions a was a function ;
so that

a=f (x> Hi z)

a was here the principal variable ; while
in France the breaking strength was
usually considered constant, at least for
definite varieties of material, t represent-
ed the intensity of breaking strength
under statical load, or steady load ap-
plied once for all, and was called the
" statical breaking strength " ; u was
called the "primitive strength," and was
the greatest intensity of stress not pro-
ducing rupture when indefinitely alter-
nated with complete release from stress;
and s, called "vibration -strength," was
the greatest intensity of the stress not
producing rupture when repeated in op-
posite senses alternately.

The most important point in Dr.
Weyrauch's paper was the distinction
between resistance to rupture by stat-
ical and repeated loading. Wohler's
experiments had shown u to be much
less than t, but it was not so fully

proved that a difference (similar in de-
gree) existed between s and u. It was
reasonable, however, to believe that if
the effect of intermittent stress was
greater than that of permanent stress,
that of alternation of opposite stresses,
would be greater still. On the basis of
the three coefficients, t, u, s, were found-
ed those new formulas of resistance
which had been used in Germany since
Wohler's experiments.

The author repeats at length the
reasoning given in Dr. Weyrauch's paper,
by which Launhardt's and Weyrauch's
formulas had been arrived at, and goes
on to remark that the series of equations
which led to Launhardt's formula, relat-
ing to repetition of stress in one sense
only, might cause it to be thought ra-
tional, although really empirical. The
close correspondence between values
given by it and certain experimental re-
sults of Wohler accounted for its general
vise in Germany. But Weyrauch's form-
ula still lacked confirmation by experi-
ment. After a brief reference to Wey-
rauch's ingenious application of the
formulas devised for simple longitudinal
stress to long pillars liable to flexure, it
is urged that the ideas on which the
formulas in question were founded must
be recognized as of great novelty and of
real practical interest, and might be
regarded as a first step towards a better
comprehension in the future of the influ-
ence of repetition and alternation of
stress on the working strength of mate-
rials. As yet they could not be said to
be fully established, and being empirical
in their character could only be judged
by a comparison of their results with
those sanctioned by experience. A typi-
cal example might be usefully quoted.
Eequired the limiting intensity of stress
to be adopted in the case of a bridge
girder, for which the ratio of dead to
total load was 1 to 3.5. . The* formula
gave for answer 800 kilograms per square
centimeter, and that was precisely the
value which would have been fixed by
practical judgment alone without calcu-
lation.

Wohler's experiments were valuable in
directing attention to the changes which
-might occur in the constitution of mate-
rials, but they did not conclusively show
that breaking strength was a safer basis
for limits of working stress than the

ON WKYKAlCIl's FORMULAS FOB THE STRENGTH OF MATERIALS. 51fi

limit of elasticity. Experience with
wrought-iron axles showed thai after
being successively twisted and untwisted
a greed many times a fibrous structure

developed which was not at first
visible. The facets seen, when fractures
thus produced were microscopically ex-
amined, were apparently caused by the
rubbing together of the ends o( tin1 fibers
previously broken in detail. From
Wohler's experiments it appeared that
similar, though less marked, changes in
molecular arrangements occurred much
re rupture. The author admitted
that the limit of elasticity was not a con-
stant quantity : experiments on the flex-
ure of rails, made by himself, having
shown that the material remained elastic
up to the stress to which it was last
subjected. Nevertheless, the possibility
of artificially raising the limit of elastic-
ity was of little or no advantage to the
material, since its condition then ap-
proached that of a brittle substance, and
the same faith could not be placed in its
permanent durability when strained.
Wohler's experiments furnished no evi-
dence that repetition of stress below the
elastic limit produced changed molecular
relations in the material. Until proof of
such changes was obtained the empirical
formulas of Launhardt and Weyrauch
could not be accepted, and the primitive
limit of elasticity would remain the safest
and most natural basis for the working-
formulas of resistance.

In conclusion, fif. Tresca draws atten-
tion to the fact that, at the Conservatoire
des Arts et Metiers, there are some plate-
dynamometer springs which have been
employed in experimental service for the
last thirty years, and had in that time
suffered rapidly repeated deflections,
which might now be numbered by mil-
lions. The greatest permitted deflection
of these springs corresponded nearly to
their elastic limit, and as yet no signs of
deterioration were visible. He thought
the objections raised against the limit of
elasticity, as a basis for working stress,
had been effectually refuted, providing
that in all cases when it was so employed
the primitive elastic limit suffered no
alteration.

By T. Seybig.

Dr. "Weyrauch's method of calculating
dimensions, was founded upon a long

series oi experiments, made by W6hler

between IS. IS and 1870, and rep.
later by Spangenburg. Certain proposi

tions had been deduced by the former
from his own experiments, which were
known collectively as Wohler's law, and
were thus expressed :

1. A piece experiencing repeated ap-
plications of stress alternating bet v.
certain maximum and minimum values,
ultimately breaks under a less intensity of
stress than would produce rupture if
gradually applied once.

'2. The number of repetitions produc-
ing rupture increases as the maximum
stress is diminished, the minimum si
to which the piece returns after each
repetition remaining constant.

3. The number of repetitions produc-
ing rupture increases as the minimum
stress is increased, the maximum stress
remaining constant.

4. "When the maximum intensity of
stress does not exceed a certain limit, ay
rupture does not occur, whatever the
number of repetitions.

5. That limiting intensity, a, increases
as the minimum stress is increased.

The author exemplifies these proposi-
tions separately by the results of some of
the experiments, and also illustrates 2
and 3 by diagrams in which the number
of repetitions required for rupture are
represented by ordinates whose corre-
sponding abscissas representedthe varia-
ble maximum or minimum stresses which
alternated with a fixed minimum or max-
imum stress respectively. The experi-
ments wTere made chiefly on specimens of
iron and steel from the Phonix and Krupp
Works, and, though not numerous or
embracing much variety of material, suf-
ficed to show a much greater similarity
between the nature of iron and steel
than had been hitherto supposed. Thus
the ratio of a to u was. for wrought iron
fo and for steel, -x85-. Jt was necessary
to observe that, owing to the very rapid
repetition of the stress, there wras no in-
terval of repose between its successive
applications. In large metallic struc-
tures such intervals usually occurred,
and it might be that the disturbed
molecules then returned more complete-
ly to their primitive positions and con-
dition of resistance — an important ques-
tion that remained for future investiga-
tion. A table is given, containing all the

ai6

VAN NOSTRAND'S ENGINEERING MAGAZINE.

yalues of the constants a, u and 5,
which the experiments had fur-
nished ; and a detailed explanation of
certain formulas devised by Prof. Wink-
ler, upon the basis of those values, which
might suit intermediate values of «, more
exactly than those of Launhardt and
Weyrauch, comparing them with the
latter both graphically and numerically.
The author admits the importance of the
limit of elasticity, but thinks that W0J1-
ler's experiments showed the need for
fully considering the conditions under
which the forces were applied to the
pieces of a machine or structure ; in the
former, quick repetition and motion ; in
the latter, the varying conditions pro-
duced jby the moving load. Most speci-
fications prescribed the minimum break-
ing strength and corresponding elonga-
tion, but not usually the limit of elastic-
ity. It now appeared, however, that the
latter was not constant, M. Tresca hav-
ing found that it might be raised to
near the limit of rupture ; and under
certain conditions of alternating opposite
stresses, Wohler had found rupture to
occur below the primitive value of the
elastic limit, which under these condi-
tions must have bfeen lowered. Woh-
ler's experiments required further con-
firmation, but still they sufficed to dis-
credit those uniform limits of working
stress, the use of which was at least as
unfavorable to economy as to security.
For if the conclusions of Launhardt,
Weyrauch, and Winkler were accepted,
a limiting stress, double of that hitherto
adopted in France, might, in some cases,
be worked to with the same margin of
safety, thus giving greater economy ;
while in other cases two-thirds only of
the usual limiting stress appeared per-
missible ; many existing structures being
therefore less secure than had been sup-
posed.

By E. E. Marche.

Although the experiments of Wohler
had been made too carefully to permit
doubt, either of- their accuracy or of the
truth of the law founded upon them, it
was otherwise with the new formulas
deduced from that law by other German
writers, and they should not be accepted
without investigation. The existence of
the " primitive strength " k, was a direct

conclusion from Wohler's experiments,
and Mr. Seyrig's diagrams showed it to
be the abscissa of the vertical asymptote
to the curve representing the variation in
the number of repetitions of any given
stress required to produce rupture, and
its accurate determination, was neces-
sarily difficult. After quoting in detail
some experiments of Wohler's on Phonix
iron and Krupp steel by repeated flexure,
the author infers that, from the entire
number of experiments made, two values
only of u could be deduced, viz., 22
kilograms per square millimeter for
wrought iron, and 37 kilograms for steel.
These were, sensibly, the primitive limits
of elasticity of the some materials, and
it was indeed remarkable that the German
experimenters should propose to super-
sede the limit of elasticity by a new con-
stant, which was only the same thing
under another name. That rupture
necessarily followed the repeated appli-
cation of stress above the limit of elas-
ticity he thought was scarcely yet fully
proved. He conceived that when rup-
ture occurred through repetition of stress
below the statical breaking strength, it
was due to alteration in the molecular
state of the material, produced by
vibration and manifested by diminished
cohesion or by displacement of the limit
of elasticity. Future experiments should
tell something more than the mere num-
ber of repetitions required to produce
rupture. After a certain number of
repetitions the limit of elasticity and
breaking strength should be again de-
termined, in order to ascertain whether
and to what extent their primitive
values had been altered. Wohler's ex-
periments showed with certainty that
stress below the elastic limit may be
alternated an indefinite number of times
with any less stress of the same sense,
or with zero, without fear of rupture or
molecular alteration of the material.
But the experiments on alternate tension
and compression which had led to the
coefficient s and Weyrauch' s formula
deserved serious attention, and suggested
the need for diminished limits of work-
ing stress in such circumstances. He
held that, for repeated stress of one
sense only, it was sufficient to fix the
working stress at one-third of the limit
of elasticity ; and that, in the case of
alternations of equal stresses of opposite

REPORTS OF ENGIJN BERING SOCIETJ E8.

517

senses, one-third of the value found for
8 might be use. I.

iota which had been ascertained
i>\ M Tresca and others, relative to per-
manent deformation were of great im-

ince, but since fchey only existed when
and because the elastic limit was pas
they should not be used as data for

listing the strength of materials
which, by the very conditions of their
employment, were required to remain
elastic and not to become modified or

irmed.

showed that its character should l>c ac-
curately determined and the fact a- of
Bafety fixed with due regard to crircum-

stan.

By E. Trelat.

The author believes the limit of elas-
ticity t<> be a more satisfactory basis for
limits for working stress than the break-
ogth. The business of an engi-
neer was fo so design the different mem-
of a structure that the greatest
loads should produce no visible perma-
nent changes of their form and dimensions-
Por brittle materials, such as stone,
which suffered no permanent change of
form before breaking, deformation was
proportional to the force producing it up
to rupture ; and it was therefore right to
fix the safe working load as a fraction of
the breaking strength. For those ma-
terials which could experience permanent
deformation before rupture, experiment
had shown their resistance to comprise
two distinct periods, in the first of which
they were elastic, while in the second
they suffered permanent change of form.
The boundary between those two periods,
in other words the primitive limit of elas-
ticity, marked the limit of safe employ-
ment for such materials with due regard
to preservation of their form and dimen:
sions ; and the safe working stress
should be taken as a fraction of that
primitive limit. If the limit of elasticity
artificially raised the working stress
should be a smaller fraction of that new
limit. Future experiment in such special
- that of repeated alternation of
stress in opposite senses, might show to
what extent the primitive limit of elas-
ticity was lowered, or perhaps that it
coincided with the breaking strength
under those conditions. The existence
of the different limits of rupture indicated
by the symbols t, u, s, did not diminish
the utility of the limit of elasticity as a
standard of working resistance ; but

Bj H. Matthhu, President of the S i
oiety of (1i\il Engineers of Paris.

Experiments made by the author 25
years age showed that, by successive ap-
plications of stress, at first feeble and
gradually increased by very small and

equal increments, the breaking strength

was raised above the primitive value.

But when this process was commenced
with an initial stress equal to half the

primitive breaking strength, rupture was
produced by less stress than in the firsl
case. The limit of elasticity seemed,
therefore, to vary according to the man-
ner in which it was sought for.

While rendering full justice to the re-
markable labors of the German experi-
menters, M. Matthieu thinks that French
engineers will retain their belief in the
principle of the limit of elasticity, which
in France had served hitherto as the
basis of the theory and the practical
formulas of the strength of materials.

REPORTS OF ENGINEERING SOCIETIES.

American Society of Civil Engineers —
This Society met, Wednesday, Oct. 18th,
1882, at 8 p.m. Vice-President, Wm. H. Paine
in the chair, John Bogart, Secretary. The
death of Henrique Harris, M. Aui. Soc. C. E.,
on Oct. 10th, was announced and the prepara-
tion of a memoir was directed.

A paper by Henry D. Blunden, M. Am. Soc.
C. E. , on the Care a ad Maintenance of Iron
Bridges, was read by the Secretary. The writer
observed, that while many papers and much
discussion had been published on the design
and construction of bridges, there had been
little or nothing on the subject of their care and
maintenance after erection. Indeed, there
seems a prevalent idea that once erected, they
will last forever with no care but an occasional
coat of paint and even that is often not attend-
ed to. A close examination during nine years
past, of a large number of bridges shows con-
stant, shameful neglect. The fact is that the
immediate care of bridges is generally left to
men who know nothing, either practically or
theoretically, of their design or manufacture.
The single idea is to screw everything up light
and to replace all rivets without asking why
a rivet drops out several times in the same
place.

The paper enumerated various causes of un-
due wear in bridges ; uneven bearing of rails
and ties ; insufficient freedom of expansion
gear often caused by accumulation of dirt ; im-

518

VAN nostrand's engineering magazine.

proper anchoring of fixed ends ; poor masonry:
uneven adjustment of laterals ; uneven bearing
of suspended floors ; over tightening of count-
ers ; corrosion of iron ; false economy in con-
struction of floors, rendering renewals very
expensive ; too large joints between ends of
rails.

The writer also gives a number of suggestions
as to the proper care of bridges, particularly
insisting upon constant inspection and frequent
reports to the office of the Chief Engineer. .

The paper was discussed by Messrs. C. Mac-
donald, S.H. Shreve, Thos. Cooper, Wm. H.
Paine, J. P. Davis, W. E. Worthen, J. G.
Sanderson, C. E. Emery and J. C. Campbell
In Ihe discussion the great necessity of atten-
tion to the care of bridges in use was forcibly
brought out. Instances were mentioned of the
serious results of entrusting this duty to incom-
petent men and of the advantage found by the
few corporations now taking proper measures.
Reference was made to the great difficulty of
adjustment in bridges with parts in cast and
parts in wrought iron. A case was described
in which an iron rod in contact with sulphur
became seriously corroded. It was stated that
the ordinary commercial sulphur had an amount
of sulphuric acid sufficient to cause rust, but
that when properly washed it was safe. The
use of sulphur or lead for joints was discussed.
An ordinary misapprehension as to scale was
illustrated by an instance where the actual
amount of iron in the scale was found to be
but one-tenth of the scale. The use of lime
whitewash to protect iron was considered, and
instances of its good effect were mentioned.

T Engineers' Club op Philadelphia. — The
Lj first meeting of the season was held Oct.
7th. President Rudoldph Hering in the chair.

Mr. W. H. Cory, of England, read a paper
upon the subject of his process for the utiliza-
tion of waste dust coal, which consists of mix-
ing the coal with a small percentage of fine,
dry fire-clay and another small percentage ol
silicate of soda, and submitting the block to a
pressure of one ton to the square inch. The
blocks are then stacked to dry and in 24 hours
(the chemical action of the alumina in the clay
having convei ted the silicate of soda into sili-
cate of alumina or into an insoluble substance,
in ihat time) the blocks are fit for use, and are
as hard as ordinary coal. Among the advant-
ages claimed lor this fuel are the following ;
seven per cent, more work than ordinary lump
coal, there being no loss from dust falling-
through the fire-bars, &c. ; that the fuel manu-
facturer can make his own silicate at little ex-
pense and trouble ; that the fuel, being com-
pressed, will stow in a much less space than
coal; that it does not smoke, smell, depreciate
in the furnace or 'cause clinker ; that the ma-
chinery is light and inexpensive; that the cost
of manufacture will not exceed fifty cents per
ton, and that all descriptions of coal can be
utilized, without deteriorating their burning
qualities. Mr. Cory exhibited samples made
from Anthracite, Bituminous and Lignite coals,
and concluded by giving statistics showing an-
nual waste of coal in dust, etc.

The secretary presented from Mr. H. M.Geer,

a discussion of that part of Mr. P. H. Baer-
mann's recent paper upon the "Thickness of
Cast Iron Pipe under Pressure," wherein he
refers to the rupture of a 12" pipe by the ram
upon the sudden closing of a 2%" opening, un-
der 230' head, by the breaking of a hydrant.

W v2
For Mr. Baermann's formula, — giving a

pressure of 2,330 lbs. per square inch, Mr. Geer

W v2

substitutes — - — =P s (P= force or resistance

3 g
and s — space over which P acts) or P —

W v2

r and obtains, assuming that the moving

2 g s

mass of water is brought to rest with a uni-
formly retarded motion, in one second 1,354
lbs. per square inch, in one-helf second 2,708
lbs. per square inch, and so on, inversely as the
time. Without knowing the actual time of the
closing of the valve and velocity of water, he
considers deductions impossible. He refers to
the reasoning of Mr. Fanning (Water Supply,
p. 449) in this connection, as likewise errone-
ous. He attributes the cause of failure to thin,
chilled and imperfect pipe, and the general
safety of pipes from effects of the ram' to the
existence of air chambers at summits of undu-
lations, the possible reflux of water to the re-
servoir, the compressibility of the yarn in the
joints and perhaps to the elasticity of the walls
of the pipe and the compressibility of the water
itself.

The Secretary presented, for Mr. Howard
Constable, a description of the KinzuaViaduct,
the highest bridge structure in the world, illus-
trated by numerous general and detail drawings
and photographs. It forms part of a branch of
the Erie Railway into the coal fields of Elk
Country, Pa., and its construction was found
to be the most economical way of crossing the
Kinzua Gorge, a long time obstacle in the way
of railroad construction.

Surveys and investigations leading to the
conception of this work, were made by Mr. O.
W..B irnes, Chief Engineer of the road before it
passed into the hands of the Erie Railway. It
was built according to Erie specifications, by
Messrs. Clarke, Reeves & Co., under Mr. O.
Chanute, Chief Engineer, assisted by Messrs.
Chas. Pugsley, H. C. Keif er and the author.
It contains 3,500,000 lbs. of iron and cost $275,-
000.

At the meeting of October 21st, Col. Living-
stone, of Philadelphia, described the system of
Driven Wells, giving various data and statis-
tics, with regard to results obtained in this and
other localities.

Dr. H. M. Chance described several horse-
shoe or ox bow bends occurring in the streams
of Western Pennsylvania, attributing the ori-
gin of each and every similar loop to syncli-
nal axes.

Loops on the Allegheny River at Brady's
Bend and at Scrubgrass (also an old abandoned
loop at Parker, two hundred feet above the
present Channel) ; on the Red Bank Creek near
Bethlehem; on Kettle Creek in Clinton County,
and old abandoned bends at Callensburg on the
Clanin River, and near Westport in Clinton

EN GIN KRRING NOTKS.

519

County, were described, the Inevitable syncli-
nal a\i^ present ai all of tbem, affording the
only explanation of ibeir origin.

ENGINEERING NOTES.

BLASTING WOBS IX THE DANUBE. — The
construction of the railway bridge across
the Danube at Peterwardein involves n Large
amount of blasting in the bed of the river,
which operations are now being carried out
under the direction of .Major Lauer, and at the
expense of the contractors for the bridge, the
Fives-Lille Company. The rock upon which
part of the fortress of Peterwardein is built de-
scends pretty steeply into the Danube. One
of the piers of the bridge will have its fouuda-

found

1,700 ft. span expedient. The Act for con-
structing a bridge at Queensferry across the
Forth was obtained in 1878, and the contract

for the construction of sir Thomas Bouch's
neat suspension bridge in two spans was made,
the preliminary works being in progress when
tin1 Tay Bridge fell. In consequence of the

latter disastt r, the directors of the Forth Bridge
Company decided not to proceed with the
works, and an Abandonment Bill was promoted
in the Session of L881. Different railway com-
panies, Interested in Becuring direct communi-
cation with the North of Scotland, objected to
the abandonment of the enterprise, and in-
structed their consulting engineers, .Messrs. .J.
Fowler, Harrison, and Harlow, to report anew
on the practicability and cost of crossing the
Forth by a bridge or otherwise, at Queensfeiry
or elsewhere. A careful reinvestigation of the

tion on this rocky slope, and it has been .

necessary ,0 level the rock for a length of 65 who e Question was accordingly made, with the

feet and a breadth of 26 feet, in order to be able
to lower with the requisite precision the cais-
son for the pier foundation. As the rock to
be removed is 88 feet below zero aud the pres-
ent level of the Dauube about 40 feet below
water, and as the current is running at a speed
of 10£ feet per second, some idea may be
formed of the difficulties of the blasting work
to be done. The method employed by Major
Lauer is consequently well suited to the oper-
ations needed; but as even with that method
considerable difficulties arise, it has been found
necessary, in this case, to construct, in the first
place, a guide-rod of a length of 65 feet, which
should resist the strong current to such an ex-
tent as to permit of the several dynamite
charges being sunk with the greatest accuracy.
After several experiments, a guide -rod has now
been constructed which meets the requirements
of the case, and enabled the workers to beirin
blasting operations on August 21. As upwards
of 10,000 cubic feet of rock have to be removed,
the work of blasting will probably last about
forty days, and thus an opportunity will be
offered for testing Major Lauer's method on a j
large scale.

rpHK Forth Bridge. — In Section G (Me-
J_ chanical Science) of the British Associ-
ation meeting at Southampton, Mr. B. Baker
read a paper on the Forth Bridge, in which it
was stated that the report of the Anthropometric
Committee showed that the average stature of a
new-born infant was 19.34 in., while the aver- !
ai;e height of the Guardsmen sent out to Egypt
was officially given at 5 ft. 10} in. These
figures had a ratio of 1 to 8.65, and as the
largest railway bridge in this country — the
Britannia BridVe — had a span of 465 ft., and
the Forth Bridge a span of 1,700 ft., the ratio
there wTas also 1 to 3 65. Hence to enable any
one to appreciate the size of the Forth Bridge
the following simple rule-of-three sum was
suggested:— As a Grenadier Guardsman is to a
new-born infant so is the Forth Bridge to the
largest railway bridge yet built in this country.

result that the directors were advised that it
Was perfectly practicable to build a bridge
across the Forth which would comply with the
requirements of the Boaid of Trade and public
safety, and that the best place of crossing was
Queensferry. The Abandonment Bill, which
had passed the Commons, was then withdrawn,
and the engineers were instructed to agree on a
design. Modifications of the original suspen-
sion bridge were then considered, and Mr.
Fowler and the writer of the paper submitted
a project for abridge on the continuous-girder
principle. Messrs. Harrison and Barlow, fully
appreciating the advantages which would per-
tain to such a bridge, as compared to a more
or less flexible suspension bridge, made inde-
pendent investigations, and suggested several
modifications, and finally the design, a model
aud plans of which were now before the meet-
ing, was unanimously agreed upon by all to be
recommended to the directors for adoption.
The directors acted upon this recommendation,
and the necessary plans were deposited, and an
Act obtained this year for constructing a con-
tinuous-girder bridge across the Forth at
Queensferry, having two spans of 1,700 ft.,
two of 675 ft., fourteen of 168 ft. and six of 50
ft., and giving a clear headway for navigation
purposes of 150 ft. above high-water spring
tides For this work Mr. Fowler and the
author of the paper were acting as engiueers.
Every one, probably, would concede that a
girder-bridge would prove stiffer than a sus-
pension bridge, but it was not so obvious that
it would be cheaper. Careful comparative es-
timates had, however, proved this to be so in
the case of the Forth Bridge. Having ex-
plained the reasons which induced the engi-
neers to fix on the length and width and other
matters connected with the design of the
bridge, the paper stated that the superstruc-
ture would be of steel. For the tension mem-
bers the steel used was to have an ultimate
tensile strength of not le<s than 30 tons, nor
more than 33 tons per square inch, with an
elongation of 20 per cent, in a length of 8 in.

Bridges a few feet larger in span than the Bri- 1 For the compression members the strength was
tannia has been built elsewhere, but they were to be from 34 tons to 37 tons, and the elonga-
baby bridges after all. It was not the physical tion 17 per cent. In making the tubes and
features of the country, but the habits of the other members, all plates and bars which can
population that rendered the construction of a be bent cold were to be so treated, and where

520

VAN nostrand's engineering magazine.

heating was esssential no work was to be done
upon the material after it had fallen to a blue
heat. The steady pressure of hydraulic presses
was to be substituted for hammering where
practicable, and annealing would be required
if the steel had been distressed in any way.
Having given details in reference to the bridge
compared with others, the paper stated that no
special difficulty would arise with respect to
the foundations. The total length of the great
continuous-girder was 5,330 ft., or, say a mile,
and of the viaduct approaches 2,754 ft., or
rather over half a mile. The piers would be
of rubble masonry, faced with granite, and
the superstructure of iron lattice girders,
with buckled -plate floor and trough-rail bear-
ers, as in the instance of the main spans. The
main girders spaced 16 ft. apart would be
placed under the railway, and there would be a
strong parapet and wind screen to protect the
trains. About 42,000 tons of steel would be
used in the superstructure of the main spans,
and 3,000 tons of wrought iron in that of the
viaduct approach. The total quantity of
masonry in the piers and foundations would
be about 125,000 cubic yards, and the estimated
cost of the entire work upon the basis of the
prices at which the original suspension bridge
was contracted for, was about £1,500,000,
though, owing to the magnitude and novelty of
the undertaking, the estimate must be taken as
approximate only, as a contract had not yet
been concluded for the works.

RAILWAY NOTES.

A capital of about eight millions would
suffice to construct the Euphrates Val-
ley Railway, including, the Nautical Gazette
thinks, stations and plant, and upon this sum
dividend earnings should not be impossible.
In the worst case a guarantee of 4 per cent,
interest would only cost Government the in-
considerable sum of £320,000 per annum, com-
pared with which the political avantages to be
obtained are immeasurably more consequen-
tial ; indeed cannot be weighed in the same bal-
ance. Besides which, the saving of seven
days in the passage of India would enable
Government to effect several economies in ad-
ministration, and in all probability to more
than save the actual outlay. About the stra-
tegic advantage of a quick alternative route
which would make us to some extent inde-
pendent of the Canal there can be no two ques-
tions. It would enable us to govern India
twice as efficiently and ten times more safely
than at present, while it would do more than
anything else to secure the peace of Europe.
Egypt and the Suez Canal would then lose
much of their political significance, and it
might be possible for continental nations— then
no longer jealous of England — to come to look
upon the Canal in the light of a commercial
water way only. All do not think with the
Nautical Gazette.

A paper in the Revue Scientifique (Paris,
Sept. 2) on the railways of Europe,
gives a number of interesting data. In 1840,
America had 2,800 miles of railway in work-

ing; England, 1,275 miles; France, 310 miles;
Germany, 290 miles; Belgium, 200 miles;
Austro-Hungary, 89 miles; Russia, 16£ miles;
and Holland, 11 miles. In 1860, the United
States possessed nearly as many miles of track
as the whole of the European system, having
30,460 miles, against a European total of 31,700
miles: England was a long way ahead of
Germany in the length of her system, and
France was much behind. In 1870 these con-
ditions were altered. During the ten years the
European systems had more than doubled their
mileage, which then had a total of 64,700
miles, America at the same time having only
52,450. England still retained the lead in
Europe, and Germany and France followed
her at a considerable distance, Germany, how-
ever, being little in advance of France. In 1878
Germany possessed a much longer system than
England, having 19,260 miles against our
17,100. .On December 31, in that year, Europe
had 98,060 miles; the United States, 81,650;
India, 7,530; Canada, 7,890; and Algeria, 465
miles. The United States had the greatest mile-
agein proportion to the population, having a little
over twenty-one miles for each 10,000 persons,
and were followed by Canada with 16£ miles.
In Europe, Sweden took the lead with 6£
miles to 10,000, England only having 5£ miles.
The number of locomotives running at the
same period over all the lines referred to was
30,079, represeting a force of ten million horse
power.

IRON AND STEEL NOTES.

English Importation of Iron. — Al-
most unnoticed, a startling change has,
during the last few years, taken place in
the metallurgical world. The iron manufac-
turers of Great Britain have come to depend in
very great degree upon foreign nations for a
large part of their raw materials. If we look
back twenty years we shall find that the iron
that was made in Great Britain was made al-
most exclusively of that smelted from our own
ores; but this is far from being the case now.
A few figures will show how great has been
the growth of the demand for iron ore from
other parts. In 1861 we imported 23,408 tons
of iron ore, all, except a few hundred tons,
being brought from Spain. Taking the im-
portations in the total for periods of five years
from that date, we find that by the year 1866
the importation had risen to 49,360 tons, and
by the year 1871 to 335,033 tons. Again, in
1876 it was 673,235 tons, and in 1881 it was
2,450,696 tons; so that, roughly speaking, it
doubled itself m every year named, except that
in the last of the periods there was an increase
much more than threefold. And it is worthy
of note that Spain still supplies the great bulk
of the ore thus brought in, for last year 2,227,-
486 tons were imported from that country,
Italy and Algiers sending in the bulk of the
remainder. Sweden used to send us large
quantities of iron ore, but for the last seven
or eight years it has sent us none; and Nor-
way, once a large source of supply, sent us
only 118 tons last year; so that it is from the

ORDNANCE AM) NANA I..

521

countries of Southern Europe and Spain thai

our supplies arc drawn.

The growth of the use of Imported ores is
due to one cause, the increase of Bteel pro
duction. Until the basic process was com-
menced it \\a-> tolerably clear thai the great
bulk of the in>n ore- of Britain were not Buil
able for use in the Bteel manufacture; and thus
as the use of steel grew there was an Inevitable

i ores that were so lit. The rich districts
ofFurnessand that of West Cumberland had

that were so usable, and then' was a con-
tinuous growth of the production of these;
but there was a call beyond that that they
could supply. And, moreover, many of the
works that were on the coast could bring ores
from Spain by sea cheaper than they could
bring those by land, so that there arose the

lemand for ore that has caused the swell-

: the imports shown in the figures above
given, and that Beems likely to continue, though
probably not witli such rapidity. There is now

ematic attempt to utilize our own ores by
the basic process, and this will allow a portion
of the steel that we use to be smelted from our
own iron, ami thus will at least lessen the ra-
pidity of the growth of the imports of iron.
But the fact thai we use about 2,500,000 tons
of ore from other nations, and that they cost
with the carriage probably £1,500,000, is one
thai should be a very irreat inducement towards
the further development of any and every sys-
tem that will allow of the increasing use of our
own resources, and that would retain a very large
amount of money in this country. It is not to
be expected that any such change will be very
rapid. The imported ore and its product has
made itself well known; that made by the
basic process fiom our own ores has yet to
win its way in many quarters. But whilst
there has been only one large extension, that
of Esten, where the process has been iu use,
there is now in course of construction one that
will be equally large, and that will, in the
course of a very few months, materially add to
the production, whilst in the Shropshire and
Staffordshire districts new works are in course
of construction or in contemplation, and by
these the basic process of steel production will
be much extended, and the use of our own
ores in the steel manufacture will be extended.
It remains to be seen what effect the exten-
sion will have on the importation of ores; in
the past that importation has been affected by
political events in Spain, and that cause alone
should induce as much as possible the substi-
tution of our own ores for those the continu-
ance of the supply of which has been broken
at times. — 77ie Builder.

The following information respecting car
wheels and car wheel iron has been pub-
lished by Messrs. Whitney and Sons, of Phila
delphia, makers of wheels. Concerning the
Hamilton process, which consists of melting
together charcoal and anthracite pig irons
with Bessemer steel ends, the firm claims: —
" It has been fully demonstrated that the use
of steel brings into service many charcoal irons
that would not otherwise be available for mak-
ing wheels on account of their deficient
Vol. XXVII.— No. 6—36.

strength or absence of chilling Qualities, that
a percentage of anthracite or coke irons maj
be used without impairing the strength or

durability of the wheel, and that steel i> better
than white iron to bring up the chill in any

wheel mixture." The greatest recorded mile-
age made by Whitney wheel-, with the use of
steel, is 178,000 miles, and this is the greatest
mileage on the Pennsylvania railroad wheel
records up to 1876. It is probable that since
that lime a much higher mileage has beeo ob-
tained of which there i< no accessible reconl.
Memoranda of tests of wheel mixtures of char-
coal irons and Bteel, wrought and anthracite
iron are added thereto: —

Tensile

per Trans- Dcth c-
Charcoal with sq. in. verse, tion.

2.1 per cent, steel 83,467 7926 .00157

3$ per cent, steel 26,788 9588 .00185

8pSStSSi«iV.:|H« 7988 .00218

7^ per cent, steel ,

7} per cent, anthracite... f 28,150 9425 .00221

2 1 per cent, steel )

2± percent, wrought iron )

6± per cent, anthracite... -25,550 8750 .00221

5 percent, steel )

»E££lKg5£?j"W0O 8200 .00284

The deflection is given in decimals of an inch
per 1000 lbs. of load. Transverse strength is
reduced to show weight required to break a
bar 1 inch square, supported at one end, the
weight being applied 1 inch from point of
support. The average tensile strength per
square inch of charcoal irons used for car
wheels is 22,000 lbs.

ORDNANCE AND NAVAL.

Improved Comfouxd Armor Plates — Ex-
periments with composite armor-plates
have shown that the cracks round the points of
impact projectiles are more numerous, longer,
and deeper, the greater the degree of hardness
possessed by the steel employed, while steel be-
low a certain point of hardness does not show
any cracks, but, on the other hand, has a power
of resistance scarcely above that of ordinary
iron. With the view of preventing the forma-
tion of cracks, and of rendering practicable the
employment of a steel as hard as possible and
of the required degree of resistance, Herr II.
Reusch, of Dillingen, exposes the armor-plates,
after the steel face has been cast on, and at any
stage of the subsequent rolling, for several days
to a glowing heat in an annealing furnace, the
steel face being covered as air-tight as possible,
with a substance giving off oxygen, for instance,
pure oxides of iron. It is stated that by this
process the steel face of the plate — according
to the duration of the heating process and the
effectiveness of the substance giving off oxygen
used — is more or less decarbonized, and con-
verted into a very soft and extremely tough
material, in which cracks are not produced by
the impact of projectiles. In order to effect a
close union between the bottom plate (soft steel

522

VAN NOSTRAND S ENGINEERING MAGAZINE.

or iron) and the hard steel face cast on to it, the
inventor employs easily fluxing silicates or bor-
ates as welding agents. They are applied either
dissolved in water or as powder. The inven-
tion of Herr Reusch is protected by patent.

mome important trials have recently been
JO made in the Keyham Basin, Devonport,
with the Audacious ironclad, the new flagship
for the China station. Booms had been rigged
out from the starboard side of the ship, vary-
ing in length from 30 ft. to 40 ft., and from
these were hung wire nets protecting the
whole side of the vessel. When the booms
were lowered there were 18 ft. of netting sub-
merged, enough to defeat the action of any
torpedo, as from experiments it has been
found that the destructive radius of torpedoes
does not exceed 10 ft., and that when they
are exploded at a greater depth the weight of
the water takes the explosion downwards. The
working of the booms was most satisfactory,
demonstrating that the nets afford effectual pro-
tection.'

By Archibald
London : Mac-

B00K NOTICES

PUBLICATIONS KECEIVED.

Through the politeness of Mr. James For-
rest, Secretary of the Institution of Civil
Engineers, we have received the following
papers:

A Composite Screw Tug Boat. By John
Augustus Thompson, Student I. C. E.

The Independent Testing of Steam Engines.
By John George Maif, M. I. C. E.

Bo'ness Harbor and Dock Works. By Patrick
Walter Meik, M. I. C. E.

Recent Landslips in Cheshire. By Edward
Leader Williams, M. I. C. E.

Dioptric Apparatus in Light-Houses. By
Allan Brebner, Jun., Student I. C. E.

Buckie Harbor. By James Barron, A. I . C . E.

Seacombe Ferry Improvement Works. By
Wilfrid S. Boult, A. M. I. C. E. ; and John
James Potts, A. M. I. C. E.

Corn Mill Machinery. By William Baker,
Henry Simon and William Bishop Harding.

Coal-Washing. By Thomas Fletcher Har-
vey, A. M. I. C. E.

Keport of New York State Survey
for 1880. By James T. Gardner, Di-
rector.

Signal Service Notes No. 3. How to
Foretell Frost. By Lieutenant James
Allen.

Monthly Weather Review for Sep-
tember. Washington : Government
Printing Office.

Scuola D'Appliczione per GlTngegneri,
Annual of the Practical Engineering
School of the Roman University 1882-3.
Rome, Italy.

Manufacture of Russet Leather. By
Capt. D. A. Lyle, Ordnance Depart-
ment, Washington.

ext-Book of Geology.
Geike, LL.D , F.R.S .
millan & Co.

We can do no better than to indicate briefly
the divisions of the subject exhibited by the
table of contents.

Book I. Relations of the Earth in the Scalar
System — Form and Size of the Earth — Move-
ments of the Earth in their Geological Rela-
tions.

Book II. A general description of the parts
of the Earth — Composition of the Earth's crust
including description of the leading simple
Minerals and a short treatise on Lithology.

Book III. Dynamical Geology; Hypogene
Action; Volcanoes, Earthquakes and causes of
Metamorphism. Epigene Action. The Action
of Air and Water

Book IV. Structural Geology, Stratification
Joints, Dip, Curvature, Cleavage; The Igne-
ous Rocks and the Crystalline Schists.

Book V. Paleontology.

Book VI. Stratigraphical Geology.

Book VII. Physiographical Geology.

To students of Geology the book is indis-
p3nsable. It is large for a text book, there
being 930 pages of the text. The illustrations
435 in number are fair.

Metallurzischen Chemie. Von Carl A.
M. Balling. Bonn : Emrl Strauss .

The chemistry of the more common metal-
lurgical processes is concisely set forth in this
book with little or no attention to mechanical
methods.

The Pryo chemical processes are, however,
fully discussed, including the properties of the
different available fuels.

The application of the principles of Chem-
ical Philosophy to the calculation of quantita-
tive results is also the subject of an important
chapter.

Die Magnetelektrischen und Dynamo -
elektrischen Maschinen. By Gustav
Glaser De Cew. Vienna: A. Hartleben. $1.10.

This is one of a series of technical hand
books, and is the first to be devoted to practical
electrical science. It gives descriptions of the
leading forms of Magneto and Dynamo ma-
chines aided by excellent illustrations.

The construction and theory of secondary
batteries receive a fair share of attention.

Subscales including Verniers. By Henry
H. Ludlow, U. S. A. New York: D.
Van Nostrand. Price 30 cents.

This is a reprint in pamphlet form of an es-
say bearing this title in the October number of
this Magazine.

' The theory of all vernier measurements is con-
cisely stated, and all kinds of verniers that are
worth imitating are described and illustrated.

Das Glycerin. By Siegfried Walter Koppe.
Vienna: A. Hartleben.
The Chemical Constitution, Physical Proper-
ties, Manufacture and Uses of Glycerine, are
presented in this little German book with fair
completeness. Of course Nitro-Glycerine re-
ceives a fair share of attention.
The solvent powers of the compound in pre-

Mis* i;i,i. a N EOT B.

523

par-inn extracts for chemical purposes are
li upon at nome length.
The little essay will prove equally useful to
pharmacists and to manufacturers of explo-
sives.

Cm \ik ai. \m> Physical Analysis of
Mn MILS and Infant

By Dr. Nicholas Gerber; translated by
I)r 11. Eodemann. Now York.

This hook, as its title denotes, was originally
published on tin- Qerman language, and was
favorably received.

Professor Or. c Declam (Gesundhett V.
speaks of it as follov

One of the most difficult tusks for the chem-
ist is a well executed chemical analysis of
milk. A method for the examination of milk,
Which for hygienic purposes allows to decide
ilv and exactly the questions concerning its
quality, purity or adulteration does not exist,
but every contribution thereto must be wel-
comed. When Dr. Gerber, who for a number
of years has been actively engaged in milk in-
dustries, undertakes to give us a uniform
method of analysis for milk anc* 'ts products,
be merits our sincere thanks, in the work be-
fore me the author has omitted to criticize the
older method*, as yet in use, in order to not
extend the work uunecessarily, some by the ac-
cumulation of much scientific material the
practical scope of the book mi«rht be greatly
diminished. He confines himself solely to the
description of short though exact methods,
which are easy of execution. This communi-
cation on the copious, carefully collected and
arranged contents will suffice to bear testi-
mony as to the abundance of information to be
found in this book. Dr. Gerber'sbook is to be
highly recommended to physicians and sani-
tarians.

The present English edition has been thor-
oughly revised and has received such additions
as were warranted by the progress of science.
Many of the plates which illustrate the German
edition have been substituted by better ones
taken from the best publications on this subject,
while others not contained in the original have
been added.

MISCELLANEOUS.

Some errors in page 437 of the November is-
sue in regard to the Great Lakes are here-
by corrected.

Height of Lake Superior above mean high
water is 609 feet; of Lakes Huron and Michi-
gan, 589 feet; Lake Erie, 574 feet ; Lake On-
tario, 247 feet. Lake Huron has, moreover, a
width of 105 miles.

Code of Rules for the Erection of
Lightning Conductors.-- The following
rules, from the "Report of Lightning Rod
Conference," 1882, published by Messrs. E. &
F. X. Spon 1G Charing-Cross, have been ab-
stracted under the directions of Major V. D.
Majendie, H. M. Chief Inspector of Explosives,
and sent by the Explosive Department of the
Home Office to the occupiers of factor!* b,
magazines, or stores of explosive materials, and

to the police authorities, Reasons, based on

practical and theoretical evidence, are given at
length in the Report for each rule and recom-
mendation :

1. Material of Hod. — Copper, weighing not
less than (> ox. per foot run, the electrical con-
ductivity of which is not less than 90 per cent
of that of pure copper, either in the form of
rod, tape, or rope of stout wires; no individual
wire being less than No. 12 B.W.G. (.109 in.).
Iron may be used but should not. weigh less
than '2l4 lb per foot run

2. .Joints. — Every joint, besides being well
cleaned and screwed, scarfed, or riveted, should
be thoroughly soldered.

3. Form of Faints. — The point of the upper
terminal of the conductor should not have a
sharper angle than 90 deg. A foot below the
extreme point a copper ring should be screwed
and soldered on to the upper terminal, in which
ring should be fitted three or four sharp copper
points, each about C inches long. It is desira
ble that these points should be so platinized,
gilded, or nickel plated, as to resist oxidation.

4. A umber and //eight of upper tenninoU. —
The number of conductors or upper terminals
required will depend upon the size of the build-

J ing, the material of which it is constructed, and

i the comparative height above ground of the

i several parts. No general rule can be given

for this, except that it may be assumed that the

space protected by a conductor is, as a rule, a

i cone, the radius of whose base is equal to the

height of the conductor from the ground.

5. Ciiroaturt-x. — The rod should not be bent
abruptly round sharp corners. in no case
should the length of a curve be more than half
as long again as its chord. A hole should be
drilled in siring courses or other projecting
masomy when possible, to allow7 the rod to pass

I freely through it.

6. InvuJworfi. — The conductor should not be
kept from the building by glass or other insu-
lators, but attached to it by fastenings of the
same meial as the conductor itself is composed
of.

7. Fixing. — Conductors j-hould preferentially
be taken down the side of the building which
is most exposed to rain. They should be held
firmly, but the holdfasts should not be driven
in so tightly as to pinch the conductor or pre-
vent contraction and expansion due to changes
of temperature.

8. (Alter mttai work. — All metallic spouts,
gutters, iron doors, and other masses of metal
about the building should be ekctiically con-
nected wi h the conductor.

9. Earth connection — It is most desirable
that, wheiu ver possible, the lowi r extremity of
the conductor should be buried in permanently
damp soil. Hence proximity to rainwater
pipes and to drains or other water is desirable.
It is a very «.ood plan to bifurcate the conduc-
tor clo>e below the surface of the ground, and
to adopt two of the following methods for a
curing the e:?cape of the lightning into the
earth : (1) A strip of copper tape may be led
from the bottom of the rod to a gas or water
main— not merely lo a leaden pipe — if such
exist near enough, and be soldered to it. (2)
A tape may be soldered to a sheet of copper 3

524

YrAN NOSTRAND'S ENGINEERING MAGAZINE.

ft. x 3 ft. TV in. tbick, buried in permanently
wet earth aud surrounded by cinders or coke
(3) Many yards of copper tape may be laid in
a trench filled with coke, having not less than
18 square feet of copper exposed.

10. Protection from Theft, &c — In cases
where there is any likelihood of the copper
being stolen or injured, it should be protected
by being enclosed in an iron eas pipe reaching
10 ft. — if there is room — above ground and
some distance into the ground.

11. Painting. — Iron conductors, galvanized
or not, should be painted. It is optional with
copper ones.

12. Inspection. — When the conductor is final-
ly fixed it should, in all cases, be examined and
tested by a qualified person, and this should be
done in the case of new buildings after all work
on them is finished.

Periodical examination and testing, should
opportunities offer, are also very desirable,
especially when iron-earth connections are em-
ployed.

Zinc Foil in Boilers. — Since 1875 experi-
ments have been carried on in the French
marine, particularly, with boilers having surface
condensers; to test the efficacy of zinc leaves in
neutralizing the effect of fatty acids in the
boiler and giving rise to inoffensive products.
Commandant Frene has recently given an ac-
count of the results obtained on board the De-
saix to the French Academy of Sciences. The
zinc inside and the iron of the boiler consti-
tute a voltaic element which decomposes the
water and liberates oxygen and hydrogen. The
oxygen forms oxide #of zinc, which combines
with the fatty acids mingled with the feed
water, thus forming "soaps" of zinc which,
coating the tubes of the boilers, prevent the ad-
hesion of the salts left by evaporation. It is
easy then to brush away the fixed matter on the
tubes which is in a mealy state. As to the hy-
drogen, it behaves as MM. Gernez and Donny
have described in the Annale* de Chimie et de
Physique for 1875. Ebullition takes place by
evaporation at the surface of a gas whether dis-
solved in the liquid or clinging to the solid en-
velope of the containing vessel. If the gas is
expelled from boiling water the latter can be
superheated to 30 deg. or 40 deg. Cent, above
the normal boiling point, and in such a case
evaporation only takes place at the surface.
When the temperature of the vapor emitted
corresponds to the tension which equilibrates
the pressure exercised at the surface of the
liquid, the ebullition can be started at will by
introducing a gas bubble into the liquid. Solid
bodies operate in the same way by reason of
the film of gas adhering to them. When by
long boiling all the gas is expelled, the waiter
becomes superheated, and thus an element of
danger is iniroduced. But by the employment
of zinc in the boiler a constant supply of gas
is maintained, and all danger of superheating
is avoided. The hydrogen not only starts the
boiling, but keeps it up. It is, however, nec-
essary from time to time to take out the zinc
plates from the boiler and clean from them the
salts adhering to them, else the galvanic ac

tion will dwindle and perhaps stop altogether.
M. Frene is of opinion that the action of the
zinc is, however, not so regular as theory
might expect, and advocates the substitution
of a sure and constant mechaiical action un-
der the form of a moderate but continuous in-
jection of warm air by the lower part of the
boiler, or better still, a non-oxidizing pas, such
as carbonic acid. This plan he thinks would
produce a perfectly regular ebullition, a rapid
evaporation, a saving of fuel, and freedom from
risk. Superheating, which he figuratively calls
a sleep of the liquid, would be no longer possi-
ble. The carbonic acid could be developed by
the combination of carbonate of lime and hy-
drochloric acid.

MDe Villiees has invented a metallic al-
. loy for silvering. It consists of 80
parts of tin, 18 parts of lead, and 2 parts of sil-
ver, or 90 parts of tin, 9 parts of lead, and 1
part of silver. The tin is melted first, and when
the bath is of a brilliant white the lead is added
in grains, and the mixture stirred with a stick
of pine wood, the partially melted silver is add-
ed, and the mixture stirred again. The fire is
then increased for a little while, until the sur-
face of the bath assumes a light yellow color,
when it is thoroughly stirred up and the alloy
cast in bars. The operation is then carried out
in the following manner : The article, a knife-
blade for example, is dipped in a solution of
hydroehloric or sulphuric acid, rinsed with
clean water, dried and rubbed with a piece of
soft leather or dry sponge, and finally exposed
to a temperature of 70 deg. or 80 deg. Cent. —
158 deg. to 176 deg. Fah.— for five minutesin
a muffle, to prepare the iron or steel to receive
the alloy, by making the surface porous. If the
fron is not very good these holes are much
larger, and frequently flaws and bad places are
disclosed, which make the silvering more diffi-
cult. With steel the process goes on very regu-
larly. The article, warmed to. say, 140 deg.
Fah., is dipped in the bath, melted in a cruci-
ble -over a gentle fire. The bath must be per-
fectly fluid, and is stirred with a stick of pine
or poplar ; the surface of the bath must have a
fine white silver color. For a knife-blade an
immersion of one or two minutes is sufficient to
cover it ; larger articles require five minutes
immersion. Alter taking it out of the bath it is
dipped in cold water, or treated so as to temper
it if necessary. If left too long in cold water
it frequently becomes brittle. It is then only
necessary to rub it off dry and polish without
heating it. Articles treated in this manner
look like silver, and ring like it too,+ and with-
stand the oxidizing action of the air.- To pro-
tect them from the effect of acid liquids like
vinegar, they are dipped in a bath of amalgam,
composed of 60 parts mercury, 39 parts of tin,
and 1 part of silver ; then dipped warm into
melted silver, or electro-plated with silver to
give them the silvery look. This kind of silver-
ing is said to be very durable, and the cost com-
paratively small. If this method is as good as
the inventor represents it, the i>ciemific Ameri-
can thinks it will be preferred to nickel-plat-
ing.

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